Sandimmune (cyclosporine)

No dosing information is available for this tab.

Cyclosporine is administered orally as conventional (nonmodified) or modified formulations; the drug also is administered by IV infusion.

There is no enhanced messaging for this drug.

Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

Calcineurin Inhibitors/Mifamurtide

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Mifamurtide activates macrophages as its mechanism of action. Calcineurin inhibitors inhibit macrophages and mononuclear phagocytic function.(1)

CLINICAL EFFECTS: Concurrent use of calcineurin inhibitors may decrease the effectiveness of mifamurtide.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The UK manufacturer of mifamurtide states that concurrent use with calcineurin inhibitors is contraindicated.(1)

DISCUSSION: Because calcineurin inhibitors are thought to inhibit splenic macrophages and mononuclear phagocytic function, their concurrent use with mifamurtide is contraindicated.(1)

Cyclosporine/Aliskiren

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Aliskiren is a substrate for the P-glycoprotein (P-gp) system. Cyclosporine is a potent inhibitor of P-gp.(1)

CLINICAL EFFECTS: The concurrent use of aliskiren and cyclosporine may result in elevated levels of aliskiren. This may result in increased effect and toxicity of aliskiren such as hypotension.(1,2)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of aliskiren states that concurrent use of cyclosporine should be avoided.(1) The UK manufacturer of aliskiren states that the concurrent use of potent P-gp inhibitors such as cyclosporine is contraindicated.(2)

DISCUSSION: In a study in healthy subjects, concurrent cyclosporine (200 mg and 600 mg) increased the maximum concentration (Cmax) and area-under-curve (AUC) of aliskiren (75 mg) by 2.5-fold and 5-fold, respectively.(1,2)

Cyclosporine/Ambrisentan (> 5 MG)

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Cyclosporine may inhibit the metabolism/transport of ambrisentan by CYP3A4, OATP, and P-gp.(1,2)

CLINICAL EFFECTS: Concurrent use of cyclosporine may result in elevated levels of and toxicity from ambrisentan.(1,2)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Patients maintained on cyclosporine should receive a maximum daily dose of 5 mg of ambrisentan.(1,2)

DISCUSSION: In an open-label, parallel-treatment study, 28 healthy subjects had ambrisentan (5 mg daily) added to steady-state cyclosporine (100-150 mg BID) and 24 subjects had cyclosporine (100-150 mg BID) added to steady-state ambrisentan (5 mg daily). All drug levels were evaluated at steady-state. Ambrisentan maximum concentration (Cmax) and area-under-curve (AUC) increased 1.5-fold and 2-fold, respectively, in the presence of cyclosporine. There were no significant effects on cyclosporine levels. The addition of ambrisentan to cyclosporine was less tolerable than the addition of cyclosporine to ambrisentan therapy.(1,2)

Cyclosporine/Atorvastatin (> 10 MG)

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Unknown.

CLINICAL EFFECTS: Myopathy and muscle aches, tenderness and weakness (rhabdomyolysis) may occur with concurrent administration of HMG-CoA reductase inhibitors and cyclosporine.

PREDISPOSING FACTORS: The risk for myopathy or rhabdomyolysis may be greater in patients 65 years and older, inadequately treated hypothyroidism, renal impairment, carnitine deficiency, malignant hyperthermia, or in patients with a history of myopathy or rhabdomyolysis. Patients with a SLCO1B1 polymorphism that leads to decreased function of the hepatic uptake transporter OATP1B1 may have increased statin concentrations and be predisposed to myopathy or rhabdomyolysis.

PATIENT MANAGEMENT: Avoid the concurrent use of atorvastatin(1) with cyclosporine. If concurrent use is necessary, the dose of atorvastatin should be limited to 10 mg or less.(2) When possible use alternative therapy, such as fluvastatin at dosages of 20 mg BID or less,(3) pravastatin at dosages of 20 mg daily or less,(4) or rosuvastatin at dosages of 5 mg daily or less.(5) Patients receiving concurrent therapy should be instructed to report symptoms of muscle pain, tenderness, or weakness.

DISCUSSION: Since this reaction may occur with HMG-CoA-reductase inhibitors alone, a causal relationship is difficult to establish. However, the incidence of myopathy and rhabdomyolysis appears to increase with concurrent administration of cyclosporine. In a study in 18 renal transplant patients, atorvastatin had no effect on the pharmacokinetics of cyclosporine.(6) In a study in six liver transplant patients, atorvastatin increased the area-under-curve (AUC) of cyclosporine by 10%, which was not considered clinically significant.(7) In a study in 21 renal transplant patients, cyclosporine increased atorvastatin levels by 6.4-fold when compared to historical controls. The AUC of cyclosporine decreased by 9.5%.(8) Concurrent administration of atorvastatin (10 mg) and cyclosporine (5.2 mg/kg/day) increased atorvastatin AUC and Cmax by 8.7-fold and 10.7-fold.(1) In a study in 33 renal patients, subjects were randomized to receive either atorvastatin or cerivastatin. In the cerivastatin group, there were no significant effects on cyclosporine levels. In the atorvastatin group, 4 of 10 subjects had changes in cyclosporine trough levels of 25% or more.(9) In a study, administration of pravastatin in 11 heart transplant patients receiving cyclosporine was compared to 8 control subjects not receiving cyclosporine. Pravastatin AUC and Cmax were 7-8-fold and 12-fold higher, respectively, in subjects taking cyclosporine.(10) In a double-blind, randomized, cross-over study in 44 renal transplant patients, neither lovastatin nor pravastatin affected cyclosporine levels. Pravastatin levels after 1 day and after 28 days of concurrent therapy were 5-fold higher than historical controls. Lovastatin levels accumulated over the course of the study and by Day 28 were 20-fold higher than historical controls.(11) In a study in 31 renal transplant patients, neither pravastatin nor simvastatin affected cyclosporine levels.(12) In contrast, in a study in 44 heart transplant subjects, cyclosporine clearance was increased following the addition of simvastatin.(13) Several studies have found no effect from fluvastatin on cyclosporine pharmacokinetics.(14-18) One of these also noted no affects of cyclosporine on fluvastatin levels.(13) In contrast, a study that compared the administration of fluvastatin in 10 heart transplant to 10 healthy control subjects found that fluvastatin AUC and Cmax were 2.55-fold and 3.10-fold higher than in control subjects.(19) In an open-label study in 10 heart transplant patients, concurrent cyclosporine increased rosuvastatin AUC and Cmax by 7.1-fold and 10.6-fold, respectively, when compared to historical controls. There were no effects on cyclosporine levels.(20) Rhabdomyolysis has been reported with concurrent cyclosporine and atorvastatin.(21,22) In a PKPB model, concurrent use of atorvastatin (10 mg daily) with cyclosporine (125 mg daily for 2 months) increased the simulated Cmax ratio and AUC ratio of atorvastatin by 6.85 and 3.92, respectively.(23)

Cyclosporine/Bosentan; Sitaxsentan

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Bosentan may induce the metabolism of cyclosporine by CYP3A4.(1) The exact mechanisms behind the increased levels of bosentan is unknown, but may involve competitive inhibition for CYP3A4.(1) The exact mechanism behind the increased levels of sitaxsentan is unknown;(2,3) however, sitaxsentan may be a substrate of the OATP transporter system.(2)

CLINICAL EFFECTS: Concurrent use of bosentan and cyclosporine may result in elevated levels of and effects from bosentan, including severe headache, nausea, and vomiting, and may increase the risk of liver damage. Concurrent use may result in decreased levels and effectiveness of cyclosporine.(1) Concurrent use of sitaxsentan and cyclosporine may result in elevated levels of and effects from sitaxsentan, including severe headache, nausea, and vomiting, and may increase the risk of liver damage.(2)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of bosentan states that the concurrent use of bosentan and cyclosporine is contraindicated.(1) The Canadian(3) and UK(2) manufacturers of sitaxsentan state that the concurrent use of sitaxsentan and cyclosporine is contraindicated.

DISCUSSION: On the first day of concurrent bosentan (500 mg and 1000 mg twice daily) and cyclosporine therapy, bosentan trough concentrations (Cmin) increased 30-fold. Steady-state bosentan concentrations were 3- to 4-fold higher during concurrent cyclosporine. Side effects reported during concurrent therapy included severe headache, nausea, and vomiting. Mild decreases in blood pressure and heart rate were observed. Cyclosporine concentrations were decreased by 50%.(1) In a study in healthy subjects, administration of bosentan (250 mg to 1000 mg twice daily) and cyclosporine (300 mg twice daily, adjusted to achieve a Cmin of 200-250 ng/ml) increased dose-normalized bosentan Cmin on Day 1 and Day 8 by approximately 21-fold and 2-fold, respectively, when compared to bosentan administration alone. Cyclosporine mean dose-normalized maximum concentration (Cmax), area-under-curve (AUC), and Cmin decreased by 30%, 50%, and 60%, respectively, when compared to cyclosporine administration alone.(4,5) Concurrent use of sitaxsentan (100 mg daily) and cyclosporine (3.5 mg/kg twice daily) increased the minimum concentration (Cmin) of sitaxsentan by 6-fold. There were no effects on cyclosporine clearance.(2,3)

Cyclosporine/Daraxonrasib

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Cyclosporin competes with daraxonrasib to bind to cyclophilin A. Daraxonrasib binds to cyclophilin A and then active GTP-bound RAS to form the inhibitory tri-complex that blocks RAS signaling.(1) Daraxonrasib is a substrate for P-glycoprotein (P-gp). Cyclosporine is an inhibitor of P-gp and may increase intestinal absorption and decrease elimination of daraxonrasib.(1)

CLINICAL EFFECTS: The combined effect of cyclosporin and daraxonrasib is unknown. Concurrent use may result in decreased effectiveness or higher systemic concentrations of daraxonrasib which may increase the risk of gastrointestinal perforation, dermatologic toxicity, stomatitis, interstitial pneumonitis, or gastrointestinal adverse effects (nausea/vomiting/diarrhea).(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of daraxonrasib states that concurrent use of daraxonrasib and cyclosporine should be avoided.(1)

DISCUSSION: Concurrent use of daraxonrasib and cyclosporine may alter daraxonrasib pharmacokinetics, efficacy, and safety as a result of cyclosporine binding to cyclophilin A.(1) In a pharmacokinetic model, concurrent use of daraxonrasib with quinidine (300 mg three times daily, P-gp inhibitor) increased daraxonrasib area-under-the-curve (AUC) 1.8-fold.(1)

Cyclosporine/Dronedarone

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Cyclosporine may inhibit the metabolism of dronedarone by CYP3A4.(1) Dronedarone may inhibit the metabolism of cyclosporine by CYP3A4.(2)

CLINICAL EFFECTS: Concurrent use of cyclosporine with dronedarone may result in elevated levels of and toxicity from dronedarone and cyclosporine, including serious infections, nephrotoxicity, hepatotoxicity, and prolongation of the QTc interval and life-threatening cardiac arrhythmias, which may lead to torsades de pointes.(1)

PREDISPOSING FACTORS: The risk of QT prolongation or torsade de pointes may be increased in patients with cardiovascular disease (e.g. heart failure, myocardial infarction, history of torsade de pointes, congenital long QT syndrome), hypokalemia, hypomagnesemia, hypocalcemia, bradycardia, female gender, or advanced age.(3) Concurrent use of more than one drug known to cause QT prolongation or higher systemic concentrations of either QT prolonging drug are additional risk factors for torsade de pointes. Factors which may increase systemic drug concentrations include rapid infusion of an intravenous dose or impaired metabolism or elimination of the drug (e.g. coadministration with an agent which inhibits its metabolism or elimination, and/or renal/hepatic dysfunction).(3)

PATIENT MANAGEMENT: The US manufacturer of dronedarone states that concurrent administration of cyclosporine is contraindicated.(1) If alternatives are not available and concurrent therapy is deemed medically necessary, obtain serum calcium, magnesium, and potassium levels and monitor ECG at baseline and at regular intervals. Correct any electrolyte abnormalities. Instruct patients to report any irregular heartbeat, dizziness, or fainting.

DISCUSSION: Concurrent use of ketoconazole (a strong CYP3A4 inhibitor) with dronedarone increased the area-under-curve (AUC) and maximum concentration (Cmax) of dronedarone by 17-fold and 9-fold, respectively.(1)

Cyclosporine/Fluv (>20BID); Pit; Prav (>20); Ros (>5); Simva

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Cyclosporine is a CYP3A4, P-glycoprotein, and OATP inhibitor, while statins are CYP3A4, P-glycoprotein, and OATP substrates. (18,30) When a statin is combined with cyclosporine, statin clearance is reduced and elevated statin concentrations remain in the peripheral blood and muscle cells.(31)

CLINICAL EFFECTS: Myopathy and muscle aches, tenderness and weakness (rhabdomyolysis) may occur with concurrent administration of HMG-CoA reductase inhibitors and cyclosporine.

PREDISPOSING FACTORS: The risk for myopathy or rhabdomyolysis may be greater in patients 65 years and older, inadequately treated hypothyroidism, renal impairment, carnitine deficiency, malignant hyperthermia, or in patients with a history of myopathy or rhabdomyolysis. Patients with a SLCO1B1 polymorphism that leads to decreased function of the hepatic uptake transporter OATP1B1 may have increased statin concentrations and be predisposed to myopathy or rhabdomyolysis. Patients on fluvastatin who are CYP2C9 intermediate or poor metabolizers may have increased fluvastatin concentrations and risk of myopathy. Patients on rosuvastatin with ABCG2 polymorphisms leading to decreased or poor BCRP transporter function may have increased rosuvastatin concentrations and risk of myopathy.

PATIENT MANAGEMENT: The dosage of fluvastatin should not exceed 20 mg BID in patients receiving cyclosporine.(1) The concurrent use of pitavastatin with cyclosporine is contraindicated.(2) The dosage of pravastatin should not exceed 20 mg in patients receiving cyclosporine.(3) The dosage of rosuvastatin should not exceed 5 mg in patients receiving cyclosporine.(4) The concurrent use of simvastatin with cyclosporine is contraindicated.(5-7) Patients receiving concurrent therapy should be instructed to report symptoms of muscle pain/tenderness/weakness, fever, unusual tiredness, and/or a change in the amount of urine.

DISCUSSION: Since this reaction may occur with HMG-CoA-reductase inhibitors alone, a causal relationship is difficult to establish. However, the incidence of myopathy and rhabdomyolysis appears to increase with concurrent administration of cyclosporine. In a study, administration of a single dose of cyclosporine (2 mg/kg) on Day 6 of pitavastatin (2 mg daily) increased the AUC and Cmax of pitavastatin by 4.6-fold and 6.6-fold, respectively.(2) In a study, administration of pravastatin in 11 heart transplant patients receiving cyclosporine was compared to 8 control subjects not receiving cyclosporine. Pravastatin AUC and Cmax were 7-8-fold and 12-fold higher, respectively, in subjects taking cyclosporine.(8) In a double-blind, randomized, cross-over study in 44 renal transplant patients, neither lovastatin nor pravastatin affected cyclosporine levels. Pravastatin levels after 1 day and after 28 days of concurrent therapy were 5-fold higher than historical controls. Lovastatin levels accumulated over the course of the study and by Day 28 were 20-fold higher than historical controls.(9) In a study in 31 renal transplant patients, neither pravastatin nor simvastatin affected cyclosporine levels.(10) In contrast, in a study in 44 heart transplant subjects, cyclosporine clearance was increased following the addition of simvastatin.(11) In a study, a single dose of cyclosporine (5 mg/kg) increased the Cmax and AUC of a single dose of pravastatin (40 mg) by 327% and 282%, respectively.(3) Several studies have found no effect from fluvastatin on cyclosporine pharmacokinetics.(12-16) One of these also noted no affects of cyclosporine on fluvastatin levels.(12) In contrast, a study that compared the administration of fluvastatin in 10 heart transplant to 10 healthy control subjects found that fluvastatin AUC and Cmax were 2.55-fold and 3.10-fold higher than in control subjects.(17) In another study, stable cyclosporine doses increased the Cmax and AUC of fluvastatin (20 mg daily for 14 weeks) by 30% and 90%, respectively.(1) In an open-label study in 10 heart transplant patients, concurrent cyclosporine increased rosuvastatin AUC and Cmax by 7.1-fold and 10.6-fold, respectively, when compared to historical controls. There were no effects on cyclosporine levels.(4,18) Rhabdomyolysis has been reported with concurrent cyclosporine and lovastatin(19-23) and simvastatin.(24-29)

Cyclosporine/Lercanidipine

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Cyclosporine, a moderate inhibitor of CYP3A4, may inhibit the metabolism of lercanidipine.(1)

CLINICAL EFFECTS: The concurrent use of lercanidipine and cyclosporine may result in elevated levels of lercanidipine. This may result in increased effects of lercanidipine.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of lercanidipine states that concurrent use of lercanidipine and cyclosporine is contraindicated.(1)

DISCUSSION: In a study in healthy volunteers, concurrent administration of lercanidipine and cyclosporine increased lercanidipine's plasma concentration 3-fold and cyclosporines area-under-the-curve (AUC) by 21%.(1)

Cyclosporine/Letermovir (> 240 MG)

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Cyclosporine, an OATP1B1/3 inhibitor, may inhibit the metabolism of letermovir. Letermovir, a moderate CYP3A4 inhibitor, may inhibit the metabolism of cyclosporine.(1)

CLINICAL EFFECTS: The concurrent administration of cyclosporine and letermovir may result in elevated levels of letermovir and/or cyclosporine.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of letermovir states that if oral or intravenous letermovir is coadministered with cyclosporine, the dosage of letermovir should be decreased to 240 mg once daily in adult and pediatric patients 12 years of age or older in the following populations: - Hematopoietic stem cell transplantation (HSCT) recipients weighing at least 30 kg, or - Kidney transplant recipients weighing at least 40 kg.(1) If cyclosporine is initiated after starting letermovir, the next dose of letermovir should be decreased to 240 mg once daily.(1) If cyclosporine is discontinued after starting letermovir, the next dose of letermovir should be increased to 480 mg once daily.(1) If cyclosporine dosing is interrupted due to high cyclosporine levels, no dose adjustment of letermovir is needed.(1) The manufacturer of letermovir states that if oral or intravenous letermovir is coadministered with cyclosporine in pediatric HSCT recipients 6 months to less than 12 years of age, or 12 years of age and weighing less than 30 kg, the dosage of letermovir may require adjustment as outlined: - 30 kg and above: Daily dose of letermovir = 240 mg - 15 kg to less than 30 kg: Daily dose of letermovir = 120 mg - 7.5 kg to less than 15 kg: Daily dose of letermovir = 60 mg - 6 kg to less than 7.5 kg: Daily dose of letermovir = 40 mg If cyclosporine is initiated after starting letermovir, the next dose of letermovir should be the daily oral or intravenous dose co-administered with cyclosporine.(1) If cyclosporine is discontinued after starting letermovir, the next dose of letermovir should be the daily oral or intravenous dose administered without cyclosporine.(1) If cyclosporine dosing is interrupted due to high cyclosporine levels, no dose adjustment of letermovir is needed.(1) Refer to letermovir prescribing information for dosing recommendations based on patient age and weight.(1) Frequently monitor cyclosporine whole blood concentrations during treatment and after discontinuation of letermovir and adjust the dose of cyclosporine accordingly.(1)

DISCUSSION: In a study, concurrent administration of cyclosporine (200 mg single dose, oral) with letermovir (240 mg once daily, oral) increased letermovir's area-under-the-curve (AUC), maximum concentration (Cmax), and trough concentration (C24hr) by 2.11-fold, 1.48-fold, and 2.06-fold.(1) In a study, concurrent administration of cyclosporine (50 mg single dose, oral) with letermovir (240 mg once daily, oral) increased cyclosporine's AUC and C24hr by 1.66-fold and 2.19-fold.(1)

Cyclosporine/Tacrolimus

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Both tacrolimus and cyclosporine are nephrotoxic. Additionally, both drugs are highly protein bound, and extensively metabolized by CYP3A4, increasing risk for elevated serum concentrations. When taken together they may cause additive or synergistic nephrotoxicity.(1-3)

CLINICAL EFFECTS: Concurrent use of tacrolimus and cyclosporine may result in nephrotoxicity.(1-3)

PREDISPOSING FACTORS: Patients with baseline hypertension and/or taking high doses of cyclosporine may have an increased risk of an adverse effect.(4)

PATIENT MANAGEMENT: The manufacturer of tacrolimus states that tacrolimus should not be used simultaneously with cyclosporine. When switching patients from one agent to another, the first agent should be discontinued for at least 24 hours prior to beginning the new agent. In patients with elevated levels of tacrolimus or cyclosporine, allow additional time between agents.(1) If concurrent therapy is used, renal function, specifically serum creatinine, should be closely monitored. If severe impairment occurs, consider a dose reduction of tacrolimus or alternative treatment.(2-3)

DISCUSSION: Tacrolimus is extremely nephrotoxic. Initial clinical experience with concurrent tacrolimus and cyclosporine resulted in additive/ synergistic nephrotoxicity.(1) A prospective study evaluated treatment regimens for patients who had a liver transplant within the last year and had calcineurin inhibitor (CNI)-induced renal dysfunction. 75 patients were randomized to either continue their current CNI dose or switch to mycophenolate mofetil (MMF) with a reduced CNI dose. Compared to baseline there was a statistically significant improvement in renal function in the MMF group. Changes in renal function for the CNI group were not statistically significant. This study suggests an alternative treatment regimen for patients with CNI-induced renal impairment.(5)

Cyclosporine; Sirolimus/Adagrasib

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Adagrasib may decrease the metabolism and increase the absorption of cyclosporine and sirolimus by inhibiting CYP3A4 and P-glycoprotein (P-gp).(1)

CLINICAL EFFECTS: Concurrent use of adagrasib may result in elevated levels of and toxicity from cyclosporine and sirolimus.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of adagrasib states that concurrent administration of sensitive narrow therapeutic index P-glycoprotein substrates or sensitive CYP3A4 substrates (e.g. cyclosporine, sirolimus) with adagrasib should be avoided.(1)

DISCUSSION: Concurrent adagrasib (600 mg twice daily) increased the area-under-curve (AUC) and maximum concentration (Cmax) of digoxin by 1.5-fold and 1.9-fold, respectively.(1) In a study, adagrasib (400 mg twice daily) increased the AUC and Cmax of a single dose of midazolam by 21-fold and 4.8-fold, respectively. In a study, adagrasib (600 mg twice daily) increased the AUC and Cmax of a single dose of midazolam by 31-fold and 3.1-fold, respectively.(1)

Immunosuppressive; Immunomod/Cladribine Onc Inj (10 MG/5 ML)

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Cladribine in combination with immunosuppressives and immune-modulators all suppress the immune system.(1-2)

CLINICAL EFFECTS: Concurrent use of cladribine with immunosuppressive or immune-modulating agents may result in an increased risk of serious infections.(1-2)

PREDISPOSING FACTORS: Incomplete washout of previously prescribed immunosuppressive or immune-modulating medications.

PATIENT MANAGEMENT: Recommendations for cladribine regarding this interaction differ between regulatory approving agencies. The UK and AU manufacturers of Litak state that concomitant use of other myelosuppressive medicinal products with cladribine is contraindicated.(1-2) The Israeli manufacturer of Litak states that cladribine should not be used concomitantly with other myelosuppressive medicinal products.(3)

DISCUSSION: The risk of severe myelotoxicity and long-lasting immunosuppression is increased in patients with a disease-related bone marrow infiltration or a previous myelosuppressive treatment.(1-3)

Immunosuppressives; Immunomodulators/Efalizumab; Natalizumab

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Natalizumab,(1-3) efalizumab,(4) immunosuppressives, and immunomodulators all suppress the immune system.

CLINICAL EFFECTS: Concurrent use of natalizumab(1-3) or efalizumab(4) with immunosuppressives or immunomodulators may result in an increased risk of infections, including progressive multifocal leukoencephalopathy (PML), an opportunistic infection caused by the JC virus (JCV).

PREDISPOSING FACTORS: Previous JCV infection, longer duration of natalizumab treatment - especially if greater than 2 years, and prior or concomitant treatment with immunosuppressant medication are all independent risk factors which increase the risk for PML.(1,5) The FDA has estimated PML incidence stratified by risk factors: If anti-JCV antibody positive, no prior immunosuppressant use and natalizumab treatment less than 25 months, incidence <1/1,000. If anti-JCV antibody positive, history of prior immunosuppressant use and natalizumab treatment less than 25 months, incidence 2/1,000 If anti-JCV antibody positive, no prior immunosuppressant use and natalizumab treatment 25-48 months, incidence 4/1,000 If anti-JCV antibody positive, history of prior immunosuppressant use and natalizumab treatment 25-48 months, incidence 11/1,000.

PATIENT MANAGEMENT: The US manufacturer of natalizumab states patients with Crohn's disease should not receive concurrent immunosuppressants, with the exception of limited overlap of corticosteroids, due to the increased risk for PML. For new natalizumab patients currently receiving chronic oral corticosteroids for Crohn's Disease, begin corticosteroid taper when therapeutic response to natalizumab has occurred. If corticosteroids cannot be discontinued within six months of starting natalizumab, discontinue natalizumab.(3) The US manufacturer of natalizumab states that natalizumab should not ordinarily be used in multiple sclerosis patients receiving immunosuppressants or immunomodulators due to the increased risk for PML. Immunosuppressives include, but are not limited to azathioprine, cyclophosphamide, cyclosporine, mercaptopurine, methotrexate, mitoxantrone, mycophenolate, and corticosteroids.(3,6) The UK manufacturer of natalizumab states that concurrent use with immunosuppressives or antineoplastic agents is contraindicated.(1) The Canadian manufacturer of natalizumab states that natalizumab should not be used with immunosuppressive or immunomodulatory agents.(2) The US manufacturer of certolizumab states that concurrent therapy with natalizumab is not recommended.(7)

DISCUSSION: Progressive multifocal leukoencephalopathy has been reported in patients receiving concurrent natalizumab were recently or concomitantly taking immunomodulators or immunosuppressants.(1-5,8,9) In a retrospective cohort study of multiple sclerosis patients newly initiated on a disease-modifying therapy, use of high-efficacy agents (alemtuzumab, natalizumab, or ocrelizumab) resulted in the same risk of overall infections as moderate-efficacy agents, but there was an elevated risk of serious infections (adjusted hazard ratio [aHR] = 1.24, 95% confidence interval (CI) = 1.06-1.44) and UTIs (aHR = 1.21, 95% CI = 1.14-1.30).(10)

Oatp1b1-3 Inhibitors/Atrasentan

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: OATP1B1 and 1B3 inhibitors may increase the absorption and/or decrease the hepatic uptake of atrasentan.(1)

CLINICAL EFFECTS: Concurrent use of OATP1B1 or 1B3 inhibitors may result in elevated levels of and side effects from atrasentan, including fluid retention and hepatotoxicity.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of atrasentan states that concurrent use of OATP1B1 or 1B3 inhibitors should be avoided.(1)

DISCUSSION: In a clinical study, atrasentan maximum concentration (Cmax) was 4.3 times higher and area-under-curve (AUC) was 3.8 times higher following coadministration of a single dose of 0.75 mg atrasentan with cyclosporine (OATP1B1 and 1B3 inhibitor) compared to atrasentan alone. OATP1B1 and OATP1B3 inhibitors include: atazanavir, belumosudil, boceprevir, clarithromycin, cobicistat, cyclosporine, eltrombopag, erythromycin, fostemsavir, gemfibrozil, glecaprevir-pibrentasvir, leflunomide, leniolisib, letermovir, lopinavir, nirmatrelvir, ombitasvir-paritaprevir, resmetirom, ritonavir, roxadustat, saquinavir, simeprevir, telaprevir, teriflunomide, tipranavir, vadadustat, velpatasvir, voclosporin, and voxilaprevir.(1,2)

Oatp1b1-3 Inhibitors/Elbasvir-Grazoprevir

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Inhibitors of OATP1B1/3 may decrease the hepatocyte uptake and increase the plasma concentrations of elbasvir and grazoprevir.(1-3)

CLINICAL EFFECTS: Concurrent use of an inhibitor of OATP1B1/3 may result in elevated levels of grazoprevir and an increased risk of ALT elevations.(1-3)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Concurrent use of elbasvir-grazoprevir and OATP1B1/3 inhibitors is contraindicated.(1-2,4) If concurrent use is deemed medically necessary, monitor the patient for toxicity and elevated AST levels.

DISCUSSION: In a study in 10 subjects, atazanavir/ritonavir (300/100 mg daily) increased the maximum concentration (Cmax), area-under-curve (AUC), and minimum concentration (Cmin) of elbasvir (50 mg daily) by 4.15-fold, 4.76-fold, and 6.45-fold, respectively. There were no clinically significant effects on atazanavir levels.(1,2) In a study in 12 subjects, atazanavir/ritonavir (300/100 mg daily) increased the Cmax, AUC, and Cmin of grazoprevir (200 mg daily) by 6.24-fold, 10.58-fold, and 11.64-fold, respectively. There were no clinically significant effects on atazanavir levels.(1,2) In a study in 14 subjects, cyclosporine (400 mg single dose) increased the Cmax, AUC, and Cmin of elbasvir (50 mg daily) by 1.95-fold, 1.98-fold, and 2.21-fold, respectively. The Cmax, AUC, and Cmin of grazoprevir (200 mg daily) increased by 17-fold, 15.21-fold, and 3.39-fold, respectively. There were no clinically significant effects on cyclosporine levels.(1,2) In a study in 10 subjects, darunavir/ritonavir (600/100 mg twice daily) increased the Cmax, AUC, and Cmin of elbasvir (50 mg daily) by 1.67-fold, 1.66-fold, and 1.82-fold, respectively. There were no clinically significant effects on darunavir levels.(1,2) In a study in 13 subjects, darunavir/ritonavir (600/100 mg twice daily) increased the Cmax, AUC, and Cmin of grazoprevir (200 mg daily) by 5.27-fold, 7.50-fold, and 8.05-fold, respectively. There were no clinically significant effects on darunavir levels.(1,2) In a study in 10 subjects, lopinavir/ritonavir (400/100 mg twice daily) increased the Cmax, AUC, and Cmin of elbasvir (50 mg daily) by 2.87-fold, 3.71-fold, and 4.58-fold, respectively. There were no clinically significant effects on lopinavir levels.(1,2) In a study in 13 subjects, lopinavir/ritonavir (400/100 mg twice daily) increased the Cmax, AUC, and Cmin of grazoprevir (200 mg daily) by 7.31-fold, 12.86-fold, and 21.70-fold, respectively. There were no clinically significant effects on lopinavir levels.(1,2) In single dose studies, rifampin increased levels of both elbasvir and grazoprevir. In a study in 14 subjects, rifampin (600 mg single IV dose) increased the Cmax, AUC, and Cmin of a single dose of elbasvir (50 mg) by 41%, 22%, and 31%, respectively. In a study in 14 subjects, rifampin (600 mg single oral dose) increased the Cmax, AUC, and Cmin of a single dose of elbasvir (50 mg) by 29%, 17%, and 21%, respectively. In a study in 12 subjects, rifampin (600 mg single IV dose) increased the Cmax, AUC, and Cmin of a single dose of grazoprevir (200 mg) by 10.94-fold, 10.21-fold, and 1.77-fold, respectively. In a study in 12 subjects, rifampin (600 mg single oral dose) increased the Cmax, AUC, and Cmin of a single dose of grazoprevir (200 mg) by 6.52-fold, 8.35-fold, and 1.61-fold, respectively.(1) OATP1B1/3 inhibitors include: atazanavir, belumosudil, cyclosporine, darunavir, fostemsavir, leniolisib, letermovir, lopinavir, nirmatrelvir/ritonavir, paritaprevir, resmetirom, roxadustat, saquinavir, tipranavir, vadadustat, and voclosporin.(1-3)

Oatp1b3 Inhibitors/Zavegepant

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Zavegepant is a substrate of the organic anion transporting polypeptide 1B3 (OATP1B3) transporter. Inhibitors of OATP1B3 may increase zavegepant exposure.(1)

CLINICAL EFFECTS: Concurrent use of OATP1B3 inhibitors may result in increased levels of and toxicity from zavegepant.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Concurrent administration of zavegepant with OATP1B3 inhibitors should be avoided.(1)

DISCUSSION: In a study, rifampin (an OATP1B3 and NTCP inhibitor) at steady state increased the area-under-curve (AUC) and maximum concentration (Cmax) of zavegepant by 2.3-fold and 2.2-fold. Since rifampin is also a CYP3A4 inducer and zavegepant is metabolized by CYP3A4, concurrent use of zavegepant with other OATP1B3 inhibitors that are not CYP3A4 inducers may have an even more significant effect on zavegepant exposure.(1) OATP1B3 inhibitors include: atazanavir, belumosudil, cobicistat, cyclosporine, darolutamide, enasidenib, encorafenib, fostemsavir, glecaprevir/pibrentasvir, leflunomide, leniolisib, letermovir, lopinavir/ritonavir, paritaprevir, resmetirom, rifampin, ritonavir, teriflunomide, velpatasvir, voclosporin, and voxilaprevir.(2-9)

P-Glycoprotein (P-GP) Inh/Colchicine (FOR CARDIOPROTECTION)

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: P-glycoprotein (P-gp) inhibitors may affect the transport of colchicine, a P-gp substrate.(1,2)

CLINICAL EFFECTS: Concurrent use of a P-gp inhibitor may result in elevated levels of and toxicity from colchicine. Symptoms of colchicine toxicity include abdominal pain; nausea or vomiting; severe diarrhea; muscle weakness or pain; numbness or tingling in the fingers or toes; myelosuppression; feeling weak or tired; increased infections; and pale or gray color of the lips, tongue, or palms of hands.(1,2)

PREDISPOSING FACTORS: This interaction is expected to be more severe in patients with renal or hepatic impairment.(1,2)

PATIENT MANAGEMENT: The manufacturer of colchicine used for cardiovascular risk reduction states that concurrent use of colchicine with P-gp inhibitors is contraindicated.(1)

DISCUSSION: There are several reports of colchicine toxicity(3-5) and death(6,7) following the addition of clarithromycin to therapy. In a retrospective review of 116 patients who received clarithromycin and colchicine during the same hospitalization, 10.2% (9/88) of patients who received simultaneous therapy died, compared to 3.6% (1/28) of patients who received sequential therapy.(8) An FDA review of 117 colchicine-related deaths that were not attributable to overdose found that 60 deaths (51%) involved concurrent use of clarithromycin.(2) There is one case report of colchicine toxicity with concurrent erythromycin.(9) In a study in 20 subjects, pretreatment with diltiazem (240 mg daily for 7 days) increased the maximum concentration (Cmax) and area-under-curve (AUC) of a single dose of colchicine (0.6 mg) by 44.2% (range -46.6% to 318.3%) and by 93.4% (range -30.2% to 338.6%), respectively.(1) In a study in 24 subjects, pretreatment with verapamil (240 mg twice daily for 7 days) increased the Cmax and AUC of a single dose of colchicine (0.6 mg) by 40.1% (range -47.1% to 149.5%) and by 103.3% (range -9.8% to 217.2%), respectively.(1) Colchicine toxicity has been reported with concurrent use of CYP3A4 and P-gp inhibitors such as clarithromycin, cyclosporine, diltiazem, erythromycin, and verapamil.(1,2) P-gp inhibitors include abrocitinib, amiodarone, asciminib, asunaprevir, aumolertinib, azithromycin, belumosudil, capmatinib, carvedilol, cimetidine, cyclosporine, danicopan, daraxonrasib, daridorexant, deutivacaftor, diltiazem, diosmin, dronedarone, erythromycin, flibanserin, fluvoxamine, fostamatinib, glecaprevir/pibrentasvir, imlunestrant, ivacaftor, lapatinib, ledipasvir, mavorixafor, neratinib, osimertinib, pirtobrutinib, propafenone, quinidine, ranolazine, schisandra, selpercatinib, sotorasib, tepotinib, valbenazine, velpatasvir, vemurafenib, venetoclax, vepdegestrant, verapamil, vimseltinib, and voclosporin.(1,10,11)

P-Glycoprotein (P-GP) Inhibitors/Doxorubicin

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: P-glycoprotein (P-gp) inhibition may increase doxorubicin cellular concentration, as well as decrease biliary or renal elimination.(1)

CLINICAL EFFECTS: Increased cellular or systemic levels of doxorubicin may result in doxorubicin toxicity, including cardiomyopathy, myelosuppression, or hepatic impairment.(1)

PREDISPOSING FACTORS: The interaction magnitude may be greater in patients with impaired renal or hepatic function.

PATIENT MANAGEMENT: Avoid the concurrent use of P-gp inhibitors in patients undergoing therapy with doxorubicin.(1) Consider alternatives with no or minimal inhibition. If concurrent therapy is warranted, monitor the patient closely for signs and symptoms of doxorubicin toxicity. For patients on daraxonrasib, the manufacturer of daraxonrasib states that it should be taken at least 4 hours apart from P-gp substrates.(2)

DISCUSSION: Doxorubicin is a substrate of P-gp.(1) Clinical studies have identified and evaluated the concurrent use of doxorubicin and P-gp inhibitors as a target to overcome P-gp mediated multidrug resistance.(3,4) P-gp inhibitors linked to this monograph include: amiodarone, asciminib, asunaprevir, aumolertinib, azithromycin, belumosudil, capmatinib, cimetidine, cyclosporine, daclatasvir, danicopan, daraxonrasib, daridorexant, deutivacaftor, diltiazem, diosmin, dronedarone, eliglustat, erythromycin, flibanserin, fluvoxamine, fostamatinib, ginkgo, ginseng, glecaprevir/pibrentasvir, hydroquinidine, imlunestrant, istradefylline, ivacaftor, lapatinib, ledipasvir, mavorixafor, neratinib, osimertinib, paroxetine, pirtobrutinib, propafenone, quercetin, quinidine, quinine, ranolazine, sarecycline, schisandra, selpercatinib, simeprevir, sofosbuvir/velpatasvir/voxilaprevir, sotorasib, tepotinib, valbenazine, vemurafenib, vepdegestrant, verapamil, vimseltinib, and voclosporin.(5,6)

Select Immunosuppressives/Ropeginterferon Alfa-2B

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Ropeginterferon alfa-2b and immunosuppressives both suppress the immune system.

CLINICAL EFFECTS: Concurrent use of ropeginterferon alfa-2b with immunosuppressives may result in an increased risk of serious infections.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US and UK manufacturers of ropeginterferon alfa-2b state that concurrent use of ropeginterferon alfa-2b in transplant patients receiving immunosuppressive agents is contraindicated.(1-2)

DISCUSSION: In clinical trials, 20% of patients experienced leukopenia. Interferon alfa products may cause fatal or life-threatening infections.(1-2)

Select P-Gp Inhibitors/Aumolertinib

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Aumolertinib is a substrate for P-glycoprotein (P-gp). Inhibitors of P-gp may increase intestinal absorption and decrease elimination of aumolertinib.(1)

CLINICAL EFFECTS: Concurrent use with selected P-gp inhibitors may result in higher systemic concentrations of aumolertinib which may increase the risk for cardiac failure, rhabdomyolysis, thrombosis, elevated LFTs, hyponatremia, hematologic toxicity, and QT prolongation, which may result in potentially life-threatening cardiac arrhythmias like torsade de pointes (TdP).(1)

PREDISPOSING FACTORS: The risk of QT prolongation or torsades de pointes may be increased in patients with cardiovascular disease (e.g. heart failure, myocardial infarction, history of torsades de pointes, congenital long QT syndrome), hypokalemia, hypomagnesemia, hypocalcemia, bradycardia, female gender, or advanced age.(2) Concurrent use of more than one drug known to cause QT prolongation or higher systemic concentrations of either QT prolonging drug are additional risk factors for torsades de pointes. Factors which may increase systemic drug concentrations include rapid infusion of an intravenous dose or impaired metabolism or elimination of the drug (e.g. coadministration with an agent which inhibits its metabolism or elimination, genetic impairment in drug metabolism or elimination, and/or renal/hepatic dysfunction).(2) Patients with risk factors for thrombosis may be at higher risk of adverse events, including those with advanced age, obesity (BMI >30), smoking, prolonged immobilization, heart failure, hypercoagulable state, history of venous thromboembolism, malignancy, and major surgery. The risk for rhabdomyolysis may be greater in patients 65 years and older, inadequately treated hypothyroidism, renal impairment, carnitine deficiency, malignant hyperthermia, or in patients with a history of rhabdomyolysis.

PATIENT MANAGEMENT: The manufacturer of aumolertinib states concomitant administration of aumolertinib should be avoided with P-gp inhibitors.(1) If concurrent therapy is warranted, consider obtaining serum calcium, magnesium, and potassium levels and monitoring ECG at baseline and at regular intervals. Correct any electrolyte abnormalities. Instruct patients to report any irregular heartbeat, dizziness, or fainting.

DISCUSSION: Based on in vitro data, aumolertinib is a substrate of P-gp.(1) P-gp inhibitors linked to this interaction are: abrocitinib, asunaprevir, belumosudil, capmatinib, carvedilol, cimetidine, cobicistat, conivaptan, curcumin, cyclosporine, danicopan, daridorexant, diltiazem, diosmin, flibanserin, fluvoxamine, fostamatinib, ginseng, glecaprevir/pibrentasvir, grapefruit, imlunestrant, indinavir, isavuconazole, itraconazole, ivacaftor, josamycin, ketoconazole, mifepristone, neratinib, nirmatrelvir, pirtobrutinib, ritonavir, telaprevir, tepotinib, tezacaftor, tipranavir, tucatinib, valbenazine, velpatasvir, verapamil, vimseltinib, voclosporin, and voxilaprevir.(3)

Selected Agents/Mibefradil

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Mibefradil has been shown to inhibit the activity of CYP P-450-3A4 and CYP P-450-2D6 and may inhibit the metabolism of these agents.(1-2)

CLINICAL EFFECTS: Concurrent administration may result in elevated levels of these agents.(1,2) Withdrawal of mibefradil may result in decreased levels of these agents. Concurrent administration of the mibefradil with the HMG-CoA reductase inhibitors may result in elevated levels of the HMG-CoA reductase inhibitors, which may result in rhabdomyolysis.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Patients who received concurrent therapy with mibefradil and these agents should be monitored for decreased levels and effectiveness of these medications during the two weeks following the withdrawal of mibefradil. Dosage adjustments of the medications may be necessary. The manufacturer of mibefradil stated that concurrent administration of mibefradil with either lovastatin or simvastatin was contraindicated and that concurrent administration of mibefradil with either atorvastatin or cerivastatin should have generally been avoided.(1) Fluvastatin or pravastatin, which are not significantly metabolized by CYP P-450-3A4, may have been used as alternatives in patients receiving mibefradil.

DISCUSSION: Mibefradil was shown to inhibit CYP P-450-3A4 and CYP P-450-2D6 thus may inhibit the metabolism of agents metabolized at these sites. Withdrawal of mibefradil may result in decreased levels of these agents as the CYP P-450 system returns to normal. Following the discontinuation of mibefradil, seven to 14 days are required for sufficient elimination of mibefradil metabolites to minimize mibefradil effects on the CYP P-450 system. Dosage adjustments may need to be made during this period.(2) The manufacturer stated that there were seven reports of rhabdomyolysis in patients receiving concurrent therapy with simvastatin and mibefradil. Four patients were also receiving cyclosporine. Because lovastatin follows the same metabolic pathway as simvastatin, a similar interaction would be expected. Atorvastatin and cerivastatin are metabolized by CYP P-450-3A4 to active and inactive metabolites.(1)

Selected Cyp3a4 Substrates/Mifepristone

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Mifepristone is an inhibitor of CYP3A4 and may increase levels and effects of drugs metabolized by this enzyme.(1)

CLINICAL EFFECTS: Lovastatin, simvastatin and CYP3A4 substrates with a narrow therapeutic window such as alprazolam, cyclosporine, dihydroergotamine, ergotamine, pimozide, quinidine, sirolimus, and tacrolimus or CYP3A4 substrates with a high first pass effect such as oral midazolam, sildenafil, and triazolam are particularly susceptible to significant toxicity.(1,2)

PREDISPOSING FACTORS: Due to the need for continuous therapy and mifepristone's long half-life of 85 hours(1) which leads to accumulation, patients with endogenous Cushing's syndrome may be at an increased risk for toxicity. With pimozide, the risk of anticholinergic toxicities including cognitive decline, delirium, falls and fractures is increased in geriatric patients using more than one medicine with anticholinergic properties.(3)

PATIENT MANAGEMENT: The US manufacturer of mifepristone for hypercortisolism due to endogenous Cushing's syndrome states use with lovastatin, simvastatin, CYP3A4 substrates with a narrow therapeutic range, or CYP3A4 substrates with a high first pass effect is contraindicated.(1)

DISCUSSION: Administration of mifepristone 1200 mg daily for 10 days followed by a single dose of simvastatin 80 mg led to an increase of simvastatin and simvastatin acid (active metabolite) area-under-curve (AUC) of 10.4-fold and 15.7-fold, respectively.

Selected Immunosuppressants/Conivaptan

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Conivaptan increases plasma levels of cyclosporine, sirolimus, and temsirolimus by inhibition of CYP3A4.(1-4)

CLINICAL EFFECTS: Concurrent conivaptan may result in elevated levels of and toxicity from cyclosporine, sirolimus, and temsirolimus.(1-4)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of conivaptan states that concomitant use of drugs eliminated primarily by CYP3A-mediated metabolism should be avoided.(1) Cyclosporine, sirolimus, or temsirolimus levels and renal function should be monitored if conivaptan is initiated or discontinued from concurrent therapy. The dosage of cyclosporine, sirolimus, or temsirolimus may need to be adjusted. The US manufacturer of sirolimus states that concurrent therapy with moderate CYP3A4 inhibitors such as conivaptan should be used with caution. The dosage of sirolimus or conivaptan may require adjustment.(3)

DISCUSSION: Erythromycin 800 mg every 8 hours, a moderate CYP3A4 and P-gp inhibitor, given to 24 healthy volunteers increased the maximum concentration (Cmax) and area-under-curve (AUC) of sirolimus 2 mg by 4.4-fold and 4.2-fold, respectively.(3) In a study of 18 healthy volunteers, diltiazem 120 mg, a moderate CYP3A4 inhibitor and P-gp inhibitor, increased the Cmax and AUC of sirolimus 10 mg by 1.4-fold and 1.6-fold, respectively.(3) In 25 healthy volunteers, verapamil 180 mg twice daily, a moderate CYP3A4 inhibitor and P-gp inhibitor, increased the max and AUC of sirolimus 2 mg by 2.3-fold and 2.2-fold, respectively.(3) Concurrent administration of ketoconazole, another inhibitor of CYP3A4, had no effects on temsirolimus AUC or Cmax; however, sirolimus AUC and Cmax increased 3.1-fold and 2.2-fold, respectively. Dosage adjustment of temsirolimus to 12.5 mg/week in the presence of strong CYP3A4 inhibitors is expected to adjust levels to the range observed without inhibitors; however, there are no data available with this dose adjustment.(4)

Selected Immunosuppressants/Nadofaragene Firadenovec

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Nadofaragene firadenovec may contain low levels of replication-competent adenovirus.(1)

CLINICAL EFFECTS: Concurrent use of nadofaragene firadenovec in patients receiving immunosuppressive therapy may cause disseminated adenovirus infection.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Individuals who are immunosuppressed or immune-deficient should not receive nadofaragene firadenovec.(1)

DISCUSSION: Nadofaragene firadenovec is a non-replicating adenoviral vector-based gene therapy but may contain low levels of replication-competent adenovirus. Immunocompromised persons, including those receiving immunosuppressant therapy, may be at risk for disseminated adenovirus infection.(1)

Selected Immunosuppressants/Talimogene Laherparepvec

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Talimogene laherparepvec is a live, attenuated herpes simplex virus.(1)

CLINICAL EFFECTS: Concurrent use of talimogene laherparepvec in patients receiving immunosuppressive therapy may cause a life-threatening disseminated herpetic infection.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Talimogene laherparepvec is contraindicated in immunosuppressed patients.(1) The magnitude of immunocompromise and associated risks due to immunosuppressant drugs should be determined by a physician.

DISCUSSION: Concurrent use of talimogene laherparepvec in patients receiving immunosuppressive therapy may cause a life-threatening disseminated herpetic infection.(1)

Selected Immunosuppressants;Temsirolimus/Selected Macrolides

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Macrolide antibiotics may inhibit the metabolism of cyclosporine, sirolimus, and temsirolimus by CYP3A4.

CLINICAL EFFECTS: The concurrent administration of cyclosporine, sirolimus, or temsirolimus with a macrolide that inhibits CYP3A4 may result in elevated levels of cyclosporine, sirolimus, or temsirolimus and possible toxicity. The levels of the macrolide may also be elevated and result in toxicity.

PREDISPOSING FACTORS: Progressively decreasing renal/hepatic function.

PATIENT MANAGEMENT: Cyclosporine, sirolimus, and temsirolimus levels should be carefully monitored in patients receiving concurrent therapy with macrolide antibiotics. The dosage of cyclosporine, sirolimus, or temsirolimus may need to be adjusted during and/or after macrolide therapy or the macrolide may need to be discontinued. The dosage of the macrolide antibiotic may need to be adjusted. Guidelines from the American Society of Transplantation state that clarithromycin and erythromycin are contraindicated with sirolimus (although product labels do not contraindicate these combinations), and that the use of clarithromycin or erythromycin with cyclosporine should be avoided. If the combination must be used, lower the dose of the immunosuppressant by up to 50 % upon initiation of the antibiotic and monitor levels daily with cyclosporine or every 3rd day with sirolimus. The US manufacturer of sirolimus states that concurrent use with erythromycin, clarithromycin, or telithromycin is not recommended and should be avoided. The US manufacturer of temsirolimus recommends that concurrent therapy with strong CYP3A4 inhibitors such as clarithromycin or telithromycin be avoided. If concurrent use is warranted, a dosage reduction to 12.5 mg/week of temsirolimus should be considered. If the macrolide is discontinued, a washout period of 1 week should be allowed before adjusting the dosage of temsirolimus to previous levels.

DISCUSSION: Concomitant administration of cyclosporine and erythromycin has been shown to increase cyclosporine trough serum levels and clinical symptoms of drug toxicity. Maximum effect may be seen one week after concurrent administration. These effects reverse when erythromycin is discontinued. The interaction probably occurs with troleandomycin also. Case reports have documented increased cyclosporine and creatinine levels during concurrent administration with clarithromycin. Several studies have shown that spiramycin does not affect cyclosporine pharmacokinetics. Because studies in rats have shown that azithromycin does not affect CYP P-450, it would not be expected to interact with cyclosporine. One case report exists which describes a potential interaction between cyclosporine and azithromycin; however, the time course of the events suggest that other factors, such as the patient's failing renal graft, may have led to the increased cyclosporine levels in this patient. In a cross-over study in 16 healthy subjects, pretreatment with erythromycin (500 mg 3 times daily for 9 days) increased the maximum concentration (Cmax), area-under-curve (AUC), and half-life (T1/2) of a single oral dose of everolimus (2 mg on Day 5) by 2.0-fold, 4.4-fold, and 39%, respectively. There were no effects on erythromycin levels. In a study in 24 healthy subjects, concurrent sirolimus (2 mg daily) and erythromycin ethylsuccinate (800 mg 3 times daily) increased sirolimus Cmax, AUC, and time to Cmax (Tmax) by 4.4-fold, 4.2-fold, and 0.4 hours, respectively. Erythromycin Cmax, AUC, and Tmax were increased by 1.6-fold, 1.7-fold, and 0.3 hours, respectively. There are case reports of toxicity with concurrent sirolimus and erythromycin. Concurrent administration of ketoconazole, another inhibitor of CYP3A4, had no effects on temsirolimus AUC or Cmax; however, sirolimus AUC and Cmax increased 3.1-fold and 2.2-fold, respectively. Dosage adjustment of temsirolimus to 12.5 mg/week in the presence of strong CYP3A4 inhibitors is expected to adjust levels to the range observed without inhibitors; however, there are no data available with this dose adjustment. Azithromycin, a weak CYP3A4 inhibitor, and spiramycin, which does not inhibit the CYP P-450 system, would not be expected to interact with cyclosporine, sirolimus, or temsirolimus.

Selected Immunosuppressive Agents/Live Vaccines; Live Bcg

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: A variety of disease modifying agents suppress the immune system. Immunocompromised patients may be at increased risk for uninhibited replication after administration of live, attenuated vaccines or intravesicular BCG. Immune response to vaccines may be decreased during periods of immunocompromise.(1)

CLINICAL EFFECTS: The expected serum antibody response may not be obtained and/or the vaccine may result in illness.(1) After instillation of intravesicular BCG, immunosuppression may interfere with local immune response, or increase the severity of mycobacterial infection following inadvertent systemic exposure.(2)

PREDISPOSING FACTORS: Immunosuppressive diseases (e.g. hematologic malignancies, HIV disease), treatments (e.g. radiation) and drugs may all increase the magnitude of immunodeficiency.

PATIENT MANAGEMENT: The Centers for Disease Control(CDC) Advisory Committee on Immunization Practices (ACIP) states that live-virus and live, attenuated vaccines should not be administered to patients who are immunocompromised. The magnitude of immunocompromise and associated risks should be determined by a physician.(1) For patients scheduled to receive chemotherapy, vaccination should ideally precede the initiation of chemotherapy by 14 days. Patients vaccinated while on immunosuppressive therapy or in the 2 weeks prior to starting therapy should be considered unimmunized and should be revaccinated at least 3 months after discontinuation of therapy.(1) Patients who receive anti-B cell therapies should not receive live vaccines for at least 6 months after such therapies due to a prolonged duration of immunosuppression. An exception is the Zoster vaccine, which can be given at least 1 month after receipt of anti-B cell therapies.(1) The US manufacturer of abatacept states live vaccines should not be given during or for up to 3 months after discontinuation of abatacept.(2) The US manufacturer of live BCG for intravesicular treatment of bladder cancer states use is contraindicated in immunosuppressed patients.(3) The US manufacturer of daclizumab states live vaccines are not recommended during and for up to 4 months after discontinuation of treatment.(4) The US manufacturer of guselkumab states that live vaccines should be avoided during treatment with guselkumab.(5) The US manufacturer of inebilizumab-cdon states that live vaccines are not recommended during treatment and after discontinuation until B-cell repletion. Administer all live vaccinations at least 4 weeks prior to initiation of inebilizumab-cdon.(6) The US manufacturer of ocrelizumab states that live vaccines are not recommended during treatment and until B-cell repletion occurs after discontinuation of therapy. Administer all live vaccines at least 4 weeks prior to initiation of ocrelizumab.(7) The US manufacturer of ozanimod states that live vaccines should be avoided during and for up to 3 months after discontinuation of ozanimod.(8) The US manufacturer of siponimod states that live vaccines are not recommended during treatment and for up to 4 weeks after discontinuation of treatment.(9) The US manufacturer of ustekinumab states BCG vaccines should not be given in the year prior to, during, or the year after ustekinumab therapy.(10) The US manufacturer of satralizumab-mwge states that live vaccines are not recommended during treatment and should be administered at least four weeks prior to initiation of satralizumab-mwge.(11) The US manufacturer of ublituximab-xiiy states that live vaccines are not recommended during treatment and until B-cell recovery. Live vaccines should be administered at least 4 weeks prior to initiation of ublituximab-xiiy.(12) The US manufacturer of etrasimod states that live vaccines should be avoided during and for 5 weeks after treatment. Live vaccines should be administered at least 4 weeks prior to initiation of etrasimod.(13) The US manufacturer of emapalumab-lzsg states that live vaccines should not be administered to patients receiving emapalumab-lzsg and for at least 4 weeks after the last dose of emapalumab-lzsg. The safety of immunization with live vaccines during or following emapalumab-lzsg therapy has not been studied.(14) The US manufacturer of sibeprenlimab-szsi states live vaccines should not be given within 30 days prior to initiation or during treatment with sibeprenlimab-szsi.(15)

DISCUSSION: Killed or inactivated vaccines do not pose a danger to immunocompromised patients.(1) Patients with a history of leukemia who are in remission and have not received chemotherapy for at least 3 months are not considered to be immunocompromised.(1)

Selected Inhibitors Of Bcrp With Myelosuppression/Topotecan

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Inhibitors of the BCRP transporter may increase the intestinal absorption and hepatic uptake of topotecan.(1) Also, topotecan in combination with myelosuppressive agents may result in additive or synergistic effects on the immune system.(1)

CLINICAL EFFECTS: The concurrent administration of topotecan with an inhibitor of BCRP may result in elevated levels of topotecan and signs of toxicity. These signs may include but are not limited to anemia, diarrhea, thrombocytopenia, and increased risk of serious infections.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of topotecan states that the use of topotecan and BCRP inhibitors should be avoided. If concurrent use is warranted, carefully monitor patients for adverse effects.(1)

DISCUSSION: In clinical studies, the combined use of elacridar (100 mg to 1000 mg), a BCRP and P-gp inhibitor, increased the area-under-curve (AUC) of topotecan approximately 2.5-fold.(1) BCRP inhibitors linked to this monograph include: cyclosporine, encorafenib, leflunomide, leniolisib, momelotinib, and teriflunomide.(2,3)

Selected Inhibitors Of P-Gp Or Bcrp/Pazopanib

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Inhibitors of P-glycoprotein (P-gp) or BCRP may increase the absorption of pazopanib.(1)

CLINICAL EFFECTS: The concurrent administration of pazopanib with an inhibitor of P-glycoprotein or BCRP may result in elevated levels of pazopanib and signs of toxicity.(1)

PREDISPOSING FACTORS: The risk of QT prolongation or torsade de pointes may be increased in patients with cardiovascular disease (e.g. heart failure, myocardial infarction, history of torsade de pointes, congenital long QT syndrome), hypokalemia, hypomagnesemia, hypocalcemia, bradycardia, female gender, or advanced age.(2) Concurrent use of more than one drug known to cause QT prolongation or higher systemic concentrations of either QT prolonging drug are additional risk factors for torsade de pointes. Factors which may increase systemic drug concentrations include rapid infusion of an intravenous dose or impaired metabolism or elimination of the drug (e.g. coadministration with an agent which inhibits its metabolism or elimination, and/or renal/hepatic dysfunction).(2)

PATIENT MANAGEMENT: The US manufacturer of pazopanib states concurrent use of P-gp inhibitors or BCRP inhibitors should be avoided.(1) Monitor patients for increased side effects from pazopanib. The manufacturer of daraxonrasib states P-gp substrates should be administered at least 4 hours apart from daraxonrasib.(5) If concurrent therapy is warranted, consider obtaining serum calcium, magnesium, and potassium levels and monitoring ECG at baseline and at regular intervals. Correct any electrolyte abnormalities. Instruct patients to report any irregular heartbeat, dizziness, or fainting.

DISCUSSION: Pazopanib is a substrate of P-gp and BCRP. Inhibitors of these transporters are expected to increase pazopanib levels.(1) BCRP inhibitors linked to this monograph include: asciminib, belumosudil, clopidogrel, cyclosporine, curcumin, darolutamide, eltrombopag, enasidenib, febuxostat, fostemsavir, grazoprevir, lazertinib, leflunomide, leniolisib, momelotinib, oteseconazole, pirtobrutinib, regorafenib, resmetirom, ritonavir, rolapitant, roxadustat, tafamidis, teriflunomide, tolvaptan, turmeric, vadadustat, and zongertinib.(1,3-5) P-glycoprotein inhibitors linked to this monograph include: asunaprevir, belumosudil, capmatinib, carvedilol, cyclosporine, danicopan, daraxonrasib, daridorexant, diltiazem, flibanserin, fostamatinib, ginseng, glecaprevir/pibrentasvir, imlunestrant, isavuconazonium, ivacaftor, ledipasvir, neratinib, sofosbuvir/velpatasvir/voxilaprevir, tepotinib, tezacaftor, ticagrelor, valbenazine, verapamil, vimseltinib, and voclosporin.(3,4)

Selected Nephrotoxic Agents/Bacitracin

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Bacitracin may cause renal failure due to glomerular and tubular necrosis. Concurrent administration of other nephrotoxic agents may result in additive renal toxicity.(1-3)

CLINICAL EFFECTS: Concurrent use of bacitracin with other potentially nephrotoxic agents may result in renal toxicity.(1-3)

PREDISPOSING FACTORS: Dehydration and high-dose bacitracin may predispose to adverse renal effects.(1)

PATIENT MANAGEMENT: Health Canada states that bacitracin is contraindicated in patients with renal impairment, including those taking other nephrotoxic drugs.(1) The Canadian and US manufacturers of bacitracin state that concomitant use of bacitracin with other potentially nephrotoxic agents should be avoided.(2,3)

DISCUSSION: Renal impairment is a major toxicity of bacitracin. Cases of nephrotoxicity have been reported when bacitracin was used off-label.(1-3)

Selected P-Glycoprotein (P-GP) Inhibitors/Ensartinib

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Ensartinib is a P-glycoprotein (P-gp) substrate. P-gp inhibitors may increase the levels of ensartinib.(1)

CLINICAL EFFECTS: The concurrent administration of a P-glycoprotein (P-gp) inhibitor may result in elevated levels of and toxicity from ensartinib.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of ensartinib states that concurrent use of P-glycoprotein (P-gp) inhibitors should be avoided.(1) The manufacturer of daraxonrasib states P-gp substrates should be administered at least 4 hours apart from daraxonrasib.(4)

DISCUSSION: Ensartinib is a substrate of P-gp. Inhibitors of P-gp may increase toxicity of ensartinib.(1) Inhibitors of P-gp linked to this monograph include: abrocitinib, amiodarone, Asian ginseng (Panax ginseng), asunaprevir, aumolertinib, azithromycin, belumosudil, capmatinib, carvedilol, cimetidine, cyclosporine, danicopan, daraxonrasib, daridorexant, diosmin, eliglustat, flibanserin, fostamatinib, ginkgo biloba, glecaprevir and pibrentasvir, hydroquinidine, ivacaftor, lapatinib, mavorixafor, milk thistle (Silybum marianum), neratinib, osimertinib, propafenone, quercetin, quinidine, ranolazine, rolapitant, silibinin, silymarin, sotagliflozin, tepotinib, tezacaftor, valbenazine, velpatasvir, vemurafenib, venetoclax, vepdegestrant, vilazodone, vimseltinib, and voclosporin.(2,3)

Slt Immunosuppressants;Temsirolimus/Ensitrelvir;Nirmatrelvir

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Ensitrelvir and nirmatrelvir-ritonavir may inhibit the metabolism of cyclosporine, everolimus, sirolimus, tacrolimus, and temsirolimus by CYP3A4.(1-8)

CLINICAL EFFECTS: Concurrent use of ensitrelvir or nirmatrelvir-ritonavir may result in increased levels of and risk of toxicity from cyclosporine, everolimus, sirolimus, tacrolimus, or temsirolimus.(1-8)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The American Society of Transplantation (AST) Statement on Oral Antiviral Therapy for COVID-19 for Organ Transplant Recipients states use of nirmatrelvir-ritonavir will be challenging in transplant patients due to significant drug interactions and difficulty with therapeutic drug monitoring in outpatients with active Covid-19 infections. Alternatives such as early use of either an appropriate monoclonal antibody or outpatient intravenous remdesivir may be preferred as first line therapy in transplant patients to prevent progression.(9) The US manufacturer of nirmatrelvir-ritonavir states concurrent use with immunosuppressants should not be used if close monitoring is not feasible.(6) Specific immunosuppressant recommendations: -Cyclosporine: For therapy with nirmatrelvir-ritonavir in patients on cyclosporine, some experts recommend lowering the cyclosporine dose by 80%. -Tacrolimus: For therapy with nirmatrelvir-ritonavir in patients on tacrolimus, experts recommend holding tacrolimus for the 5-day duration of nirmatrelvir-ritonavir therapy. Tacrolimus level is recommended on day 3 to assess the need for a one-time dose of tacrolimus during nirmatrelvir-ritonavir therapy. -As soon as possible after nirmatrelvir-ritonavir therapy, cyclosporine or tacrolimus levels should be checked, and every 2-4 days thereafter until stable, to determine when to increase cyclosporine doses or resume tacrolimus.(8) -Everolimus: For therapy with nirmatrelvir-ritonavir in patients on everolimus, AST states CYP3A4 inhibitors, such as clarithromycin, ketoconazole, voriconazole, and HIV protease inhibitors, are contraindicated with everolimus. The US manufacturer of everolimus states concurrent use should be avoided with strong CYP3A4 inhibitors. -Sirolimus: The US manufacturer of nirmatrelvir-ritonavir(6) and sirolimus protein-bound injection (Fyarro)(10) state concurrent use should be avoided. -Temsirolimus: The US manufacturer of temsirolimus recommends that concurrent therapy with strong CYP3A4 inhibitors such as nirmatrelvir-ritonavir be avoided. If concurrent use is warranted, a dosage reduction to 12.5 mg/week of temsirolimus should be considered. If nirmatrelvir-ritonavir is discontinued, a washout period of 1 week should be allowed before adjusting the dosage of temsirolimus to previous levels.(2) For patients concurrently taking cyclosporine, everolimus, sirolimus, tacrolimus, or temsirolimus with nirmatrelvir, therapeutic concentration monitoring of the immunosuppressant is recommended. Although there are no specific recommendations for concurrent use of ensitrelvir with immunosuppressants, a similar approach would be prudent.

DISCUSSION: A retrospective study evaluated the interaction between cyclosporine or tacrolimus and nirmatrelvir/ritonavir in 25 solid-organ transplant recipients. Upon nirmatrelvir/ritonavir initiation, cyclosporine doses were decreased by 80% and tacrolimus was held for the duration of nirmatrelvir/ritonavir therapy. No patients had acute rejection in the 30 days following nirmatrelvir/ritonavir. In 21 patients on tacrolimus, the median tacrolimus trough concentration before and after nirmatrelvir/ritonavir therapy was 7.4 ng/mL (IQR, 6.6-8.6) and 5.2 ng/mL (IQR, 3.6-8.7), respectively. Four patients had supratherapeutic tacrolimus troughs after restarting tacrolimus. In these patients, tacrolimus was resumed at either reduced dose or at pre-nirmatrelvir/ritonavir dose 2-5 days after completion of nirmatrelvir/ritonavir therapy.(5) Concurrent use of nirmatrelvir/ritonavir with tacrolimus resulted in elevated tacrolimus levels, treatment interruption, and acute kidney injury.(12) In a case series, 12 bilateral lung transplant recipients with COVID-19 were started on nirmatrelvir/ritonavir. All patients were on immediate-release tacrolimus and prednisone, and all except one were also on mycophenolate. Patients stopped tacrolimus 10-14 hours before starting nirmatrelvir-ritonavir and had tacrolimus levels checked between days 3-5 of therapy. One patient required a supplemental 0.5 mg dose of tacrolimus during nirmatrelvir-ritonavir therapy. Six patients had trough levels within goal, and 3 patients had troughs below goal but at adequate immunosuppression level based on the clinicians' judgement. Ten of the patients resumed tacrolimus at 25% of their baseline dose at day 8, and 9 of them resumed full dose tacrolimus by day 10. One patient was hospitalized for worsening COVID-19. No patients experienced tacrolimus side effects or acute rejection.(13) In a case series of 3 renal transplant recipients, tacrolimus was held 1 day before patients started nirmatrelvir-ritonavir therapy. Two patients resumed previous doses of tacrolimus one day after finishing nirmatrelvir/ritonavir; one had stable tacrolimus levels and the other was supratherapeutic. The 3rd patient received a supplemental dose of tacrolimus on day 4 of therapy and resumed his previous dose starting on day 5, and was supratherapeutic on day 6. No patients experienced adverse effects or graft rejection. The authors state that nirmatrelvir/ritonavir is not contraindicated and tacrolimus levels can be closely monitored for patients on tacrolimus.(14) In a case report of a 67-year old patient on chronic tacrolimus therapy, after 4 days of nirmatrelvir-ritonavir she presented to the emergency department with slowed speech, fatigue, weakness, and loss of appetite. The patient's tacrolimus level was 176.4 ng/mL (normal range is 5-20 ng/mL).(15) In a case series of 4 renal transplant recipients, tacrolimus was paused during nirmatrelvir-ritonavir therapy, which resulted in stable therapeutic levels. In one patient, tacrolimus was resumed immediately and resulted in a toxic tacrolimus level. In three patients, tacrolimus was resumed at a reduced dose 24 hours after nirmatrelvir-ritonavir was stopped and resulted in therapeutic to supratherapeutic tacrolimus levels.(16) In a case report of a 39-year-old female, the patient developed a sudden increase in tacrolimus levels after starting nirmatrelvir-ritonavir.(17) In a PKPB model, tacrolimus clearance decreased to 35% and bioavailability increased by 18.7-fold after the coadministration of nirmatrelvir/ritonavir, compared with tacrolimus alone.(18) The selected immunosuppressants linked to this monograph include: cyclosporine, everolimus, sirolimus, tacrolimus, and temsirolimus.

Strong Oatp1b1 Inhibitors/Elagolix

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Strong inhibitors of OATP1B1 may decrease the hepatic uptake of elagolix.(1,2)

CLINICAL EFFECTS: Concurrent use of an inhibitor of OATP1B1 may result in elevated levels of and side effects from elagolix, including an increased risk of ALT elevations.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Concurrent use of elagolix and strong OATP1B1 inhibitors is contraindicated.(1)

DISCUSSION: Strong OATP1B1 inhibitors linked to this monograph include: belumosudil, cyclosporine, encorafenib, gemfibrozil, letermovir, paritaprevir, resmetirom, roxadustat, and vadadustat.(1,2)

Weak Cyp3a4 Inhibitors/Lemborexant (> 5 MG)

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Inhibitors of CYP3A4 may inhibit the metabolism of lemborexant.(1)

CLINICAL EFFECTS: Concurrent use of an inhibitor of CYP3A4 may result in increased levels of and effects from lemborexant, including somnolence, fatigue, CNS depressant effects, daytime impairment, headache, and nightmare or abnormal dreams.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The maximum recommended dose of lemborexant with concurrent use of a weak CYP3A4 inhibitors should not exceed 5 mg per dose.(1) For patients on avapritinib: this interaction applies only to gastrointestinal stromal tumor (GIST) patients on avapritinib 200 mg or 300 mg.(2)

DISCUSSION: Lemborexant is a CYP3A4 substrate. In a PKPB model, concurrent use of lemborexant with itraconazole increased area-under-curve (AUC) and concentration maximum (Cmax) by 3.75-fold and 1.5-fold, respectively. Concurrent use of lemborexant with fluconazole increased AUC and Cmax by 4.25-fold and 1.75-fold, respectively.(1) Weak inhibitors of CYP3A4 include: amiodarone, amlodipine, anamorelin, asciminib, avapritinib, azithromycin, Baikal skullcap, belumosudil, berberine, bicalutamide, blueberry, brodalumab, camizestrant, cannabidiol, capivasertib, chlorzoxazone, cilostazol, cimetidine, ciprofloxacin, clotrimazole, cranberry, cyclosporine, daclatasvir, daridorexant, delavirdine, dihydroberberine, diosmin, elinzanetant, everolimus, flibanserin, fosaprepitant, fostamatinib, gepotidacin, ginkgo, givinostat, glecaprevir/pibrentasvir, goldenseal, grazoprevir, isoniazid, istradefylline, ivacaftor, lacidipine, lapatinib, larotrectinib, lazertinib, leflunomide, levamlodipine, linagliptin, lomitapide, lurasidone, mavorixafor, olaparib, osilodrostat, palbociclib, pazopanib, peppermint oil, piperine, propiverine, propofol, ranitidine, ranolazine, resveratrol, roxithromycin, rucaparib, selpercatinib, simeprevir, sitaxsentan, skullcap, teriflunomide, ticagrelor, tolvaptan, trofinetide, vepdegestrant, viloxazine, vonoprazan, and ziftomenib.(1,3)

Weak Cyp3a4 Inhibitors/Ubrogepant (> 50 MG)

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Weak inhibitors of CYP3A4 may inhibit the metabolism of ubrogepant.(1)

CLINICAL EFFECTS: Concurrent use of ubrogepant with weak CYP3A4 inhibitors may result in an increase in exposure of ubrogepant.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer recommends a dosage adjustment of ubrogepant when used concomitantly with weak CYP3A4 inhibitors. Initial dose of ubrogepant should not exceed 50 mg when used concomitantly with weak inhibitors of CYP3A4. A second dose may be given within 24 hours but should not exceed 50 mg when used concurrently with weak CYP3A4 inhibitors.(1) For patients on avapritinib: this interaction applies only to gastrointestinal stromal tumor (GIST) patients on avapritinib 200 mg or 300 mg.(2)

DISCUSSION: Coadministration of ubrogepant with verapamil, a moderate CYP3A4 inhibitor, resulted in a 3.5-fold and 2.8-fold increase in area-under-curve (AUC) and concentration maximum (Cmax), respectively. No dedicated drug interaction study was conducted to assess concomitant use with weak CYP3A4 inhibitors. The conservative prediction of the maximal potential increase in ubrogepant exposure with weak CYP3A4 inhibitors is not expected to be more than 2-fold.(1) Weak inhibitors of CYP3A4 include: amiodarone, amlodipine, anamorelin, asciminib, avapritinib, azithromycin, Baikal skullcap, berberine, bicalutamide, blueberry, brodalumab, camizestrant, cannabidiol, capivasertib, chlorzoxazone, cilostazol, cimetidine, ciprofloxacin, clotrimazole, cranberry, cyclosporine, daclatasvir, delavirdine, deutivacaftor, dihydroberberine, diosmin, elinzanetant, everolimus, flibanserin, fosaprepitant, fostamatinib, gepotidacin, givinostat, glecaprevir/pibrentasvir, goldenseal, grazoprevir, isoniazid, istradefylline, ivacaftor, lacidipine, lapatinib, larotrectinib, lazertinib, leflunomide, levamlodipine, linagliptin, lomitapide, lurasidone, maribavir, mavorixafor, olaparib, osilodrostat, palbociclib, pazopanib, peppermint oil, piperine, pirtobrutinib, propiverine, propofol, ranitidine, ranolazine, resveratrol, roxithromycin, rucaparib, simeprevir, sitaxsentan, skullcap, teriflunomide, ticagrelor, tolvaptan, trofinetide, vepdegestrant, viloxazine, vonoprazan, and ziftomenib. (3,4)

Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

Bile Salt Efflux Pump (BSEP) Inhibitors/Cholic Acid

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: BSEP inhibitors, such as cyclosporine, decrease the amount of conjugated cholic acid secreted into the bile.(1)

CLINICAL EFFECTS: Concurrent use of a BSEP inhibitor may increase the accumulation of conjugated bile salts in the liver, resulting in exacerbation of liver impairment.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Avoid the concurrent use of cholic acid with BSEP inhibitors such as cyclosporine. If concurrent use is warranted, monitor serum transaminases and bilirubin. Instruct patients to report any signs of worsening liver impairment, such as yellowing of the whites of the eyes or skin, dark or brown (tea-colored) urine, pain on the right side of the stomach, bleeding or bruising that occurs more easily than normal, or increased lethargy.(1)

DISCUSSION: BSEP inhibitors, such as cyclosporine, decrease the amount of conjugated cholic acid secreted into the bile. Concurrent use of these agents with cholic acid may increase the accumulation of conjugated bile salts in the liver, resulting in exacerbation of liver impairment.(1)

Cyclosporine/Aminoglycosides

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Cyclosporine and aminoglycosides can both cause nephrotoxicity. Concurrent administration may result in an additive or synergistic risk of nephrotoxicity.(1-3)

CLINICAL EFFECTS: Concurrent use of cyclosporine with aminoglycosides may result in a higher risk of renal dysfunction, including structural kidney damage.(1-3)

PREDISPOSING FACTORS: Factors predisposing to nephrotoxicity include pre-existing renal impairment, older age, higher doses or longer treatment duration of either drug, and dehydration.(1-3)

PATIENT MANAGEMENT: Avoid the concurrent use of cyclosporine and aminoglycosides whenever possible.(2,3) If concurrent use cannot be avoided, it should be undertaken with great caution. Minimize the cyclosporine dose and monitor renal function carefully. Frequent dose adjustment may be indicated. If renal function deteriorates, the aminoglycoside may need to be decreased or discontinued.(1-4)

DISCUSSION: Coadministration of cyclosporine with other drugs that may impair renal function, like aminoglycosides, may cause additive or synergistic impairment of renal function. A meta-analysis of 30 studies that evaluated the correlation and risk factors between cyclosporine and kidney injury in allogeneic hematopoietic stem cell transplant (allo-HSCT) patients included 7 studies that examined the role of the combination with other drugs in the development of nephrotoxicity. Coadministration of aminoglycosides and amphotericin B were independent risk factors for acute or chronic kidney diseases related to cyclosporine in allo-HSCT patients.(5)

Cyclosporine/Amphotericin B

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Additive nephrotoxicity is most likely mechanism.

CLINICAL EFFECTS: May observe enhanced nephrotoxicity of one or both drugs.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Administer this combination cautiously. Monitoring of renal function is indicated. A decrease in cyclosporine dose will result in rapid reversal of cyclosporine-induced increases in creatinine. Holding the cyclosporine dose until serum levels are less than 150 ng/ml may reduce the likelihood of renal toxicity.

DISCUSSION: Documentation is lacking; however, if an interaction occurs, the consequences could be severe.

Cyclosporine/Atorvastatin (<= 10 MG); Lovastatin

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Unknown.

CLINICAL EFFECTS: Myopathy and muscle aches, tenderness and weakness (rhabdomyolysis) may occur with concurrent administration of HMG-CoA reductase inhibitors and cyclosporine.

PREDISPOSING FACTORS: The risk for myopathy or rhabdomyolysis may be greater in patients 65 years and older, inadequately treated hypothyroidism, renal impairment, carnitine deficiency, malignant hyperthermia, or in patients with a history of myopathy or rhabdomyolysis. Patients with a SLCO1B1 polymorphism that leads to decreased function of the hepatic uptake transporter OATP1B1 may have increased statin concentrations and be predisposed to myopathy or rhabdomyolysis.

PATIENT MANAGEMENT: Avoid the concurrent use of atorvastatin(1) or lovastatin(2) with cyclosporine. If concurrent use is necessary, the dose of atorvastatin should be limited to 10 mg or less.(3) When possible use alternative therapy, such as fluvastatin at dosages of 20 mg BID or less,(4) pravastatin at dosages of 20 mg daily or less,(5) or rosuvastatin at dosages of 5 mg daily or less.(6) Patients receiving concurrent therapy should be instructed to report symptoms of muscle pain, tenderness, or weakness.

DISCUSSION: Since this reaction may occur with HMG-CoA-reductase inhibitors alone, a causal relationship is difficult to establish. However, the incidence of myopathy and rhabdomyolysis appears to increase with concurrent administration of cyclosporine. In a study in 18 renal transplant patients, atorvastatin had no effect on the pharmacokinetics of cyclosporine.(7) In a study in six liver transplant patients, atorvastatin increased the area-under-curve (AUC) of cyclosporine by 10%, which was not considered clinically significant.(8) In a study in 21 renal transplant patients, cyclosporine increased atorvastatin levels by 6.4-fold when compared to historical controls. The AUC of cyclosporine decreased by 9.5%.(9) Concurrent administration of atorvastatin (10 mg) and cyclosporine (5.2 mg/kg/day) increased atorvastatin AUC and Cmax by 8.7-fold and 10.7-fold, respectively.(1) In a study in 33 renal patients, subjects were randomized to receive either atorvastatin or cerivastatin. In the cerivastatin group, there were no significant effects on cyclosporine levels. In the atorvastatin group, 4 of 10 subjects had changes in cyclosporine trough levels of 25% or more.(10) In a study, administration of cerivastatin (0.2 mg) in 12 renal transplant patients receiving cyclosporine was compared to 12 healthy control subjects not receiving cyclosporine. Plasma concentration of cerivastatin and its metabolites increased 3-fold to 5-fold.(11) In a study, administration of pravastatin in 11 heart transplant patients receiving cyclosporine was compared to 8 control subjects not receiving cyclosporine. Pravastatin AUC and Cmax were 7-8-fold and 12-fold higher, respectively, in subjects taking cyclosporine.(12) In a double-blind, randomized, cross-over study in 44 renal transplant patients, neither lovastatin nor pravastatin affected cyclosporine levels. Pravastatin levels after 1 day and after 28 days of concurrent therapy were 5-fold higher than historical controls. Lovastatin levels accumulated over the course of the study and by Day 28 were 20-fold higher than historical controls.(13) In a study in 31 renal transplant patients, neither pravastatin nor simvastatin affected cyclosporine levels.(14) In contrast, in a study in 44 heart transplant subjects, cyclosporine clearance was increased following the addition of simvastatin.(15) Several studies have found no effect from fluvastatin on cyclosporine pharmacokinetics.(16-20) One of these also noted no affects of cyclosporine on fluvastatin levels.(15) In contrast, a study that compared the administration of fluvastatin in 10 heart transplant to 10 healthy control subjects found that fluvastatin AUC and Cmax were 2.55-fold and 3.10-fold higher than in control subjects.(21) In an open-label study in 10 heart transplant patients, concurrent cyclosporine increased rosuvastatin AUC and Cmax by 7.1-fold and 10.6-fold, respectively, when compared to historical controls. There were no effects on cyclosporine levels.(22) Rhabdomyolysis has been reported with concurrent cyclosporine and atorvastatin,(23,24) cerivastatin,(25) and lovastatin.(26-30) In a PKPB model, concurrent use of atorvastatin (10 mg daily) with cyclosporine (125 mg daily for 2 months) increased the simulated Cmax ratio and AUC ratio of atorvastatin by 6.85 and 3.92, respectively.(31)

Cyclosporine/Caspofungin

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: The exact mechanism is unknown.

CLINICAL EFFECTS: The concurrent use of caspofungin and cyclosporine may result in elevated levels of caspofungin, as well as increases in alanine transaminase (ALT) and aspartate transaminase (AST) levels.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Caspofungin and cyclosporine should only be used concurrently if the potential benefits outweigh the potential risk to the patient. Patients receiving concurrent therapy who develop elevated liver function tests should be monitored and the risk/benefit of continuing concurrent therapy should be evaluated.(1)

DISCUSSION: In a clinical study, four subjects received two 3 mg/kg doses of cyclosporine on Day 10 of caspofungin (70 mg daily). Three of the four subjects developed transient elevations of ALT on Day 11 that were 2-3 times the upper limit of normal. AST levels were also elevated, but to a lesser magnitude. Eight subjects received cyclosporine (3 mg/kg) twice on Day 1 of caspofungin (35 mg daily for 3 days). Two of these subjects had a small increase in ALT (slightly above the upper limit of normal) and a slight elevation in AST. Cyclosporine (one 4 mg/kg dose or two 3 mg/kg doses) has been shown to increase the area-under-curve (AUC) of caspofungin by 35%.(1) In a study in 40 immunocompromised patients, subjects received concurrent caspofungin and cyclosporine from 1 to 290 days (median 17.5 days). Of these, 14 (35%) developed transaminase elevations greater than 5 times the upper limit of normal or greater than 3 times baseline during concurrent therapy or the 14 days afterwards. Five were considered possibly related to concurrent therapy. None developed clinical evidence of hepatotoxicity or serious hepatic events. Discontinuation of therapy because of abnormalities in hepatic enzymes from any cause occurred in 4 patients, 2 were considered related to concurrent therapy.(1) In prospective invasive aspergillosis and compassionate use studies, there were 4 patients who received concurrent therapy for 2 to 56 days. None developed increased hepatic enzymes.(1)

Cyclosporine/Coal Tar

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Concurrent use of cyclosporine and coal tar may result in excessive immunosuppression.(1)

CLINICAL EFFECTS: Concurrent use of cyclosporine and coal tar may increase the risk of skin malignancy.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of cyclosporine states that concurrent use of cyclosporine and coal tar is contraindicated in psoriasis patients because of the possibility of increased risk of malignancies.(1)

DISCUSSION: Tumors have been reported in 32 (2.2%) of 1439 psoriasis patients treated with cyclosporine in clinical trials. Tumors have been reported in an additional 7 patients in post-marketing reports. Sixteen of these reports involved skin malignancies. Coal tar was used by 3 of the patients.(1)

Cyclosporine/Colchicine

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Colchicine is metabolized and transported by CYP3A4 and P-glycoprotein (P-gp) respectively. Cyclosporine is an inhibitor of both of these pathways. Studies indicate that cyclosporine may inhibit renal secretion(4) of colchicine and decrease the hepatic secretion(5) of colchicine into the bile.

CLINICAL EFFECTS: Concurrent use of cyclosporine may result in elevated levels of and toxicity from colchicine. Symptoms of colchicine toxicity include muscle weakness or pain; numbness or tingling in the fingers or toes; myelosuppression; abdominal pain; nausea; severe diarrhea or vomiting; feeling weak or tired; increased infections; and pale or gray color of the lips, tongue, or palms of hands.(1,2) Patients with familial Mediterranean fever (FMF) may experience a higher incidence of colchicine-related gastrointestinal effects.

PREDISPOSING FACTORS: Serum colchicine levels and the risk of colchicine myopathy may be increased by renal dysfunction,(2) which may occur in renal transplant patients(3) and is common in gout.(2) This interaction is expected to be more severe in patients with renal and/or hepatic impairment(1,2) and may occur more frequently in patients with familial Mediterranean fever (FMF).

PATIENT MANAGEMENT: The concurrent use of strong P-gp inhibitors such as cyclosporine is contraindicated in patients with renal or hepatic impairment.(6,7) In patients without renal or hepatic impairment who are currently taking or have taken strong P-gp inhibitors such as cyclosporine in the previous 14 days, the dosage of colchicine should be reduced. For gout flares, the recommended dosage is 0.6 mg (1 tablet) for one dose. This dose should be repeated no earlier than in 3 days. For gout prophylaxis, if the original dosage was 0.6 mg twice daily, use 0.3 mg daily. If the original dosage was 0.6 mg daily, use 0.3 mg every other day. For Familial Mediterranean fever (FMF), the recommended maximum daily dose is 0.6 mg (may be given as 0.3 mg twice a day).(6,7) Patients should be instructed to immediately report any signs of colchicine toxicity, such as abdominal pain; significant nausea or vomiting; diarrhea; muscle weakness/pain; numbness/tingling in fingers/toes; unusual bleeding or bruising, infections, unusual weakness/tiredness, or pale/gray color of the lips/tongue/palms of hands.

DISCUSSION: In a study in 23 subjects, concurrent administration of a single dose of cyclosporine (100 mg) increased the maximum concentration (Cmax) and area-under-curve (AUC) of a single dose of colchicine (0.6 mg) by 270% (range 62% to 606.9%) and by 259% (range 75.8% to 511.9%), respectively.(7) In a case report, a renal transplant patient's cyclosporine level increased more than 9-fold the day after the initiation of colchicine. The patient also developed renal dysfunction.(1) In another report, a renal transplant patient developed renal dysfunction and myopathy two weeks after a three-day course of colchicine.(8) In a case report, a renal transplant patient developed myopathy four weeks after the addition of colchicine to his cyclosporine regimen. Prior to his transplant, he had taken colchicine for almost five years with no adverse effects.(9) In another report, a renal transplant patient developed myopathy two weeks after the addition of colchicine to cyclosporine therapy.(10) Another report describes three cases of myopathy during concurrent cyclosporine and colchicine. The patients had taken the combination for six weeks, one year, and eight years prior to developing myopathy.(11) In a retrospective review, five of ten patients (50%) who received concurrent cyclosporine and colchicine developed myopathy. There were no differences in age, transplant duration, or serum creatinine between those patients who developed myopathy and those who did not.(12) In a study in four patients with familial Mediterranean fever (FMF) who were receiving colchicine, an attempt was made to convert azathioprine to cyclosporine. All four patients developed pronounced side effects, including diarrhea and elevated serum lactic acid; three had elevated serum alanine aminotransferase (ALT) and hyperbilirubinemia; two had elevated serum creatinines; and one was hospitalized with myopathy. No patients reached therapeutic levels of cyclosporine. The authors had previously converted three colchicine-treated FMF patients to cyclosporine.(13) Another article reported that only one of eight patients with FMF tolerated concurrent cyclosporine and colchicine following renal transplantation. Two subjects only had gastrointestinal side effects, the other five had myopathy in addition to gastrointestinal side effects.(14) In another case report, a 59 year-old male renal transplant patient maintained on cyclosporine developed rhabdomyolysis with progressive quadriparesis, hematologic toxicity, and acute renal failure following the addition of colchicine (3 mg daily for 7 days) to his regimen.(15)

Cyclosporine/Digoxin

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Cyclosporine may increase the absorption of digoxin by inhibiting P-glycoprotein (P-gp).

CLINICAL EFFECTS: The pharmacological effects of digoxin may be increased resulting in toxicity. Symptoms of digoxin toxicity can include anorexia, nausea, vomiting, headache, fatigue, malaise, drowsiness, generalized muscle weakness, disorientation, hallucinations, visual disturbances, and arrhythmias.

PREDISPOSING FACTORS: Low body weight, advanced age, impaired renal function, hypokalemia, hypercalcemia, and/or hypomagnesemia may increase the risk of digoxin toxicity.

PATIENT MANAGEMENT: In patients receiving digoxin, monitor serum digoxin level when treatment with cyclosporine is instituted, increased, decreased or discontinued. Adjust the dose of digoxin accordingly.

DISCUSSION: Digoxin toxicity has been reported in two patients following the addition of cyclosporine to their treatment schedule. In two additional patients, the apparent volume of distribution and the plasma clearance of digoxin decreased by 71% and 53% respectively during concurrent administration of cyclosporine.

Cyclosporine/Everolimus

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Cyclosporine may inhibit the metabolism of everolimus by CYP3A4 and P-glycoprotein (P-gp).(1) Concurrent use may also increase the risk of nephrotoxicity.(1)

CLINICAL EFFECTS: Simultaneous use may result in nephrotoxicity and elevated levels of everolimus, as well as increase the risk of thrombotic microangiopathy/thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TMA/TTP/HUS).(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Reduced dosages of cyclosporine are required during concurrent therapy. The dosage of everolimus will need to be adjusted if cyclosporine is initiated, modified, or discontinued. Serum levels of both cyclosporine and everolimus should be monitored during concurrent therapy and whenever dosage adjustments of either agent are made. Patients receiving concurrent therapy should also be monitored for proteinuria. Renal function and hematologic parameters should be monitored as well.(1) Everolimus and cyclosporine should be administered at the same time.(1)

DISCUSSION: In a single dose study in healthy subjects, cyclosporine (Neoral, 175 mg) increased everolimus (2 mg) area-under-curve (AUC) by 168% (range: 46% to 365%) and maximum concentration (Cmax) by 82% (range: 25% to 158%).(1,2) Administration of another formulation of cyclosporine (Sandimmune, 300 mg) had no affect on everolimus Cmax, but increased everolimus AUC by 74%.(2) In clinical trials, the combination of everolimus and standard doses of cyclosporine resulted in frequent elevations of serum creatinine and higher mean and median serum creatinine levels.(1) In a study in renal allograft recipients, administration of everolimus (0.75 mg/day to 10 mg/day) had no significant effects on cyclosporine levels.(3)

Cyclosporine/Glecaprevir-Pibrentasvir

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Cyclosporine is an inhibitor of P-glycoprotein, BCRP, OATP1B1 and OATP1B3.(2) Pibrentasvir and glecaprevir are substrates of P-gp and BCRP. Glecaprevir is also a substrate of OATP1B1 and OATP1B3.(1)

CLINICAL EFFECTS: Concurrent use of cyclosporine may lead to higher systemic concentrations of glecaprevir-pibrentasvir increasing the risk for toxicity.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Glecaprevir-pibrentasvir is not recommended for use in patients requiring stable cyclosporine doses greater than 100 mg per day.(1)

DISCUSSION: In an interaction study in 12 subjects, cyclosporine (100 mg single dose) with glecaprevir-pibrentasvir (400/120 mg once daily) increased glecaprevir's maximum concentration (Cmax) only 30% and exposure (area-under-curve, AUC) 37%. respectively. In another study in 11 subjects, cyclosporine (400 mg single dose) with glecaprevir-pibrentasvir (300/120 mg daily) increased glecaprevir's Cmax and AUC by 4.51-fold and 5.08-fold, respectively. Pibrentasvir's AUC was increased 1.93-fold.(1)

Cyclosporine/Letermovir (<= 240 MG)

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Cyclosporine, an OATP1B1/3 inhibitor, may inhibit the metabolism of letermovir. Letermovir, a moderate CYP3A4 inhibitor, may inhibit the metabolism of cyclosporine.(1)

CLINICAL EFFECTS: The concurrent administration of cyclosporine and letermovir may result in elevated levels of letermovir and/or cyclosporine.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of letermovir states that if oral or intravenous letermovir is coadministered with cyclosporine, the dosage of letermovir should be decreased to 240 mg once daily in adult and pediatric patients 12 years of age or older in the following populations: - Hematopoietic stem cell transplantation (HSCT) recipients weighing at least 30 kg, or - Kidney transplant recipients weighing at least 40 kg.(1) If cyclosporine is initiated after starting letermovir, the next dose of letermovir should be decreased to 240 mg once daily.(1) If cyclosporine is discontinued after starting letermovir, the next dose of letermovir should be increased to 480 mg once daily.(1) If cyclosporine dosing is interrupted due to high cyclosporine levels, no dose adjustment of letermovir is needed.(1) The manufacturer of letermovir states that if oral or intravenous letermovir is coadministered with cyclosporine in pediatric HSCT recipients 6 months to less than 12 years of age, or 12 years of age and weighing less than 30 kg, the dosage of letermovir may require adjustment as outlined: - 30 kg and above: Daily dose of letermovir = 240 mg - 15 kg to less than 30 kg: Daily dose of letermovir = 120 mg - 7.5 kg to less than 15 kg: Daily dose of letermovir = 60 mg - 6 kg to less than 7.5 kg: Daily dose of letermovir = 40 mg If cyclosporine is initiated after starting letermovir, the next dose of letermovir should be the daily oral or intravenous dose co-administered with cyclosporine.(1) If cyclosporine is discontinued after starting letermovir, the next dose of letermovir should be the daily oral or intravenous dose administered without cyclosporine.(1) If cyclosporine dosing is interrupted due to high cyclosporine levels, no dose adjustment of letermovir is needed.(1) Refer to letermovir prescribing information for dosing recommendations based on patient age and weight.(1) Frequently monitor cyclosporine whole blood concentrations during treatment and after discontinuation of letermovir and adjust the dose of cyclosporine accordingly.(1)

DISCUSSION: In a study, concurrent administration of cyclosporine (200 mg single dose, oral) with letermovir (240 mg once daily, oral) increased letermovir's area-under-the-curve (AUC), maximum concentration (Cmax), and C24hr by 2.11-fold, 1.48-fold, and 2.06-fold.(1) In a study, concurrent administration of cyclosporine (50 mg single dose, oral) with letermovir (240 mg once daily, oral) increased cyclosporine's AUC and C24hr by 1.66-fold and 2.19-fold.(1)

Cyclosporine/Methotrexate

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Cyclosporine may inhibit the metabolism of methotrexate to its inactive metabolite, increasing its toxicity.(1) Concurrent use may result in excessive immunosuppression.(2)

CLINICAL EFFECTS: Concurrent use of cyclosporine and methotrexate may increase the levels of and toxicity from methotrexate, leading to increased risk of severe neurotoxicity, stomatitis, and myelosuppression, including neutropenia. Concurrent use may also increase the risk of malignancy.(2)

PREDISPOSING FACTORS: Risk factors for methotrexate toxicity include: - High-dose oncology regimens - Impaired renal function, ascites, or pleural effusions

PATIENT MANAGEMENT: The US manufacturer of cyclosporine states that concurrent use of cyclosporine and methotrexate in contraindicated in psoriasis patients because of the possibility of excessive immunosuppression and the subsequent risk of malignancies.(2) Cyclosporine and methotrexate can be used concurrently in the treatment of rheumatoid arthritis. CBC and liver function tests should be performed monthly in patients receiving concurrent therapy.(2)

DISCUSSION: In a study in 30 subjects with rheumatoid arthritis, concurrent cyclosporine increased methotrexate maximum concentration (Cmax) and area-under-curve (AUC) by 26% and 18%, respectively. The plasma AUC of the inactive 7-hydroxymethotrexate metabolite decreased by 80%. In 13 subjects who received a 10 mg dose of methotrexate, the urinary excretion of 7-hydroxymethotrexate decreased by 87%. There were no effects on the pharmacokinetics of cyclosporine or its metabolites.(1) A study that compared 30 rheumatoid arthritis patients who received concurrent cyclosporine and methotrexate to 30 rheumatoid arthritis patients who received cyclosporine alone found no effects by methotrexate on cyclosporine pharmacokinetics.(3) Tumors have been reported in 32 (2.2%) of 1439 psoriasis patients treated with cyclosporine in clinical trials. Tumors have been reported in an additional 7 patients in post-marketing reports. Sixteen of these reports involved skin malignancies. Methotrexate was used by 7 of the patients.(2)

Cyclosporine/Obeticholic Acid

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Inhibitors of the bile salt efflux pump (BSEP) may inhibit the secretion of the taurine conjugate of obeticholic acid into bile.(1)

CLINICAL EFFECTS: Concurrent administration of a obeticholic acid and cyclosporine may result in accumulation of conjugated bile salts and result in clinical symptoms.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Avoid concomitant use of obeticholic acid and inhibitors of the bile salt efflux pump (BSEP), such as cyclosporine. If concomitant use is deemed necessary, monitor serum transaminases and bilirubin.(1)

DISCUSSION: In vitro studies have shown the taurine conjugate of obeticholic acid is a substrate of the bile salt efflux pump (BSEP). Concomitant use of medications that inhibit BSEP may exacerbate accumulation of conjugated bile salts and result in clinical symptoms.(1) Cyclosporine in an inhibitor of BSEP.(1)

Cyclosporine/Ombitasvir-Paritaprevir-Ritonavir

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Ritonavir is an inhibitor of CYP3A4 and may inhibit the metabolism of cyclosporine by CYP3A4.(1-3)

CLINICAL EFFECTS: Concurrent use of ombitasvir-paritaprevir-ritonavir with or without dasabuvir may result in increased levels of cyclosporine.(1-3)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: For patients concurrently taking cyclosporine and either a HIV or HCV protease inhibitor, therapeutic concentration monitoring of the cyclosporine is recommended.(1-3) Guidelines from the American Society of Transplantation recommend avoiding the use of ritonavir-based antiviral regimens with cyclosporine due to an increased risk of graft loss and death. If the combination must be used, lower the dose of cyclosporine to 25-50 mg daily. Monitor drug concentrations closely.(1) The US and European manufacturer of ombitasvir-paritaprevir-ritonavir, with or without dasabuvir, states cyclosporine therapy should be reduced to one-fifth of the previous daily dose when ombitasvir-paritaprevir-ritonavir is started. Monitor cyclosporine levels and further adjust the dosage as needed.(2-3) Frequent assessment of renal function and cyclosporine-related toxicity is recommended.(2)

DISCUSSION: In an interaction study of healthy volunteers, ombitasvir-paritaprevir-ritonavir increased the AUC of cyclosporine 10 mg by 4.28-fold.(3) The combination of ombitasvir-paritaprevir-ritonavir-dasabuvir increased the AUC of cyclosporine 30 mg by 5.82-fold.(2-3) A case series described two liver transplant recipients who were stable on cyclosporine and were successfully treated for HCV reinfection with ombitasvir-paritaprevir-ritonavir. The first patient was on cyclosporine 100 mg/day and required a reduction in her cyclosporine dose to 10 mg/day. The second patient was on cyclosporine 60 mg/day and required a cyclosporine dose reduction to 10 mg/day. Neither patient had signs of liver injury suggestive of rejection.(4)

Cyclosporine/Orlistat

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: The exact mechanism is unknown. Orlistat may bind with cyclosporine in the stomach or small intestine, thus decreasing the absorption of cyclosporine.

CLINICAL EFFECTS: The concurrent administration of cyclosporine and orlistat may result in a decrease in the levels and clinical effects of cyclosporine.(1,2)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of orlistat states that cyclosporine should be administered either at least 3 hours before or after orlistat and that cyclosporine levels should be carefully monitored.(1)

DISCUSSION: In a case report, a heart-transplant patient experienced a decrease in cyclosporine trough concentration, maximum concentration (Cmax), and area-under-curve (AUC) by 47%, 86%, and 75%, respectively, following the addition of orlistat to his regimen.(3) In a case report, larger than normal doses of cyclosporine were required in a renal transplant patient who had been maintained on orlistat.(4) In a case report, a renal transplant patient experienced decreased cyclosporine levels following the addition of orlistat to her regimen, despite the administration of orlistat 2 hours before cyclosporine. However, the authors note that the patient did not follow a low-fat diet and experienced severe diarrhea which may have also contributed to poor cyclosporine absorption.(5) There are other case reports of decreased cyclosporine levels following the addition of orlistat,(6-9) including six reports received by the US Food and Drug Administration.(6) In a multiple dose study, orlistat (120 mg TID) decreased the Cmax and AUC of cyclosporine (50 mg BID) by 25% and 31%, respectively. When separated by 3 hours, orlistat (120 mg TID) decreased the Cmax and AUC of cyclosporine (50 mg BID) by 4% and 17%, respectively.(1,10)

Cyclosporine/Quinupristin-Dalfopristin; Pristinamycin

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Quinupristin-dalfopristin and pristinamycin may inhibit the metabolism of cyclosporine by CYP3A4.(1,2)

CLINICAL EFFECTS: Concurrent use of quinupristin-dalfopristin or pristinamycin and cyclosporine may result in elevated levels of cyclosporine and toxicity.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Cyclosporine levels should be carefully monitored when quinupristin-dalfopristin or pristinamycin is added to or discontinued from concurrent cyclosporine therapy.(1,2) The dosage of cyclosporine may need to be adjusted.

DISCUSSION: In a study in 24 subjects, the administration of quinupristin-dalfopristin (7.5 mg/kg three times daily for 2 days) and cyclosporine (300 mg on Day 3) resulted in increases in cyclosporine area-under-curve (AUC), maximum concentration (Cmax), and half-life by 63%, 30%, and 77%, respectively. There was a 33% decrease in cyclosporine clearance.(1) In a case report, a patient's trough cyclosporine levels increased from a range of 80-105 ng/ml to 261 ng/ml and 291 ng/ml two and three days after the addition of quinupristin-dalfopristin. The patient's cyclosporine dosage was decreased by one-third. Following the completion of quinupristin-dalfopristin therapy, cyclosporine levels decreased and the cyclosporine dosage was increased to prior levels.(2) In vitro studies have shown that quinupristin-dalfopristin significantly inhibits CYP3A4 metabolism, including that of cyclosporine.(1)

Cyclosporine/Selected Androgens

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Danazol and methyltestosterone may inhibit the metabolism of cyclosporine.

CLINICAL EFFECTS: Concurrent therapy may result in increased levels of cyclosporine, which may produce hepatic and renal dysfunction.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: If possible, avoid giving patients receiving cyclosporine danazol or methyltestosterone. If concurrent therapy is warranted, monitor cyclosporine levels as well as renal and hepatic function carefully. Cyclosporine dosage adjustments may be necessary when these agents are initiated or discontinued, as well as during concurrent therapy. Discontinuation of the androgen may be necessary.

DISCUSSION: Four case reports have documented increased cyclosporine levels during concurrent therapy with danazol.(1-4) In two of these reports, elevated cyclosporine levels persisted even after decreases in cyclosporine dosages.(1,2) One patient also experienced decreased renal function, as indicated by an increase in serum creatinine levels.(1) Cyclosporine levels returned to baseline following the discontinuation of danazol.(1-4) Two case reports have documented increased cyclosporine levels during concurrent therapy with methyltestosterone. Both patients experienced elevated cyclosporine, bilirubin, and serum creatinine levels during concurrent therapy.(5,6) In one patient, elevated cyclosporine levels persisted despite a 40% decrease in cyclosporine dosage.(5) Discontinuation of methyltestosterone resulted in a gradual return of cyclosporine levels to previous values.(5,6)

Cyclosporine/Selected Cyp3a4 Inhibitors

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: CYP3A4 inhibitors may inhibit the metabolism of cyclosporine.(1)

CLINICAL EFFECTS: Concurrent use of CYP3A4 inhibitors may result in elevated levels of and toxicity from cyclosporine.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Monitor cyclosporine levels and renal function in patients receiving concurrent therapy. Cyclosporine dosages may need to be decreased.(1) The manufacturers of gepotidacin and sevabertinib state that concurrent use of drugs that are extensively metabolized by CYP3A4 and have a narrow therapeutic window like cyclosporine should be avoided.(2,3)

DISCUSSION: In a study, renal and cardiac patients required a cyclosporine dose reduction of 15% to 48% when diltiazem, a moderate CYP3A4 inhibitor, was co-administered to maintain a cyclosporine trough similar to cyclosporine alone.(4) In a study, cyclosporine required a 25% dose reduction when co-administered with fluconazole, a moderate CYP3A4 inhibitor, to maintain a goal serum concentration similar to cyclosporine alone.(5) In a clinical study, coadministration of single-dose midazolam 2 mg (a sensitive CYP3A4 substrate) with gepotidacin (3,000 mg every 12 hours for 2 doses) increased the area-under-curve (AUC) of midazolam by 1.9-fold.(2) Selected CYP3A4 inhibitors linked to this monograph include: camizestrant, gepotidacin, and sevabertinib.

Cyclosporine/Sulfonamides

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Both cyclosporine and sulfonamides can cause serum creatinine and BUN elevations and nephrotoxicity.(1,2)

CLINICAL EFFECTS: Coadministration of sulfonamides and cyclosporine may produce additive nephrotoxicity.(1,2)

PREDISPOSING FACTORS: The risk of nephrotoxicity is higher with elderly patients and increasing doses of cyclosporine.

PATIENT MANAGEMENT: The manufacturer of trimethoprim/sulfamethoxazole states that concurrent use of cyclosporine should be avoided.(1) The manufacturer of cyclosporine states that concurrent use of drugs that may cause additive or synergistic renal impairment should be approached with caution. Renal function (especially serum creatinine) should be closely monitored. In all patients treated with cyclosporine, renal function should be assessed repeatedly by measurement of serum creatinine and BUN.(2)

DISCUSSION: It is not unusual for cyclosporine to cause elevations in serum creatinine and BUN.(2) There have been reports of marked but reversible nephrotoxicity with coadministration of trimethoprim/sulfamethoxazole (TMP/SMX) and cyclosporine in renal transplant patients.(1,3-4) A double-blind controlled trial of 132 renal transplant recipients on cyclosporine and randomized for prophylactic TMP/SMX therapy found that patients on TMP/SMX had 15% higher serum creatinine than control patients (p<0.01). However, the difference reflected trimethoprim inhibition of tubular excretion of creatinine and was reversible. There was no evidence that TMP/SMX augmented nephrotoxicity.(5)

Cyclosporine;Sirolimus;Temsirolimus/Slt Strong Cyp3a4 Inhib

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: The metabolism of cyclosporine, sirolimus, and temsirolimus by CYP3A4 may be inhibited by strong CYP3A4 inhibitors.

CLINICAL EFFECTS: Concurrent administration of strong CYP3A4 inhibitors may result in elevated levels of and toxicity from cyclosporine, sirolimus, or temsirolimus.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Cyclosporine, sirolimus, or temsirolimus levels and renal function should be monitored if strong CYP3A4 inhibitors are initiated or discontinued from concurrent therapy. The dosage of cyclosporine, sirolimus, or temsirolimus may need to be adjusted. The manufacturer of ribociclib states that caution is recommended when ribociclib is administered with CYP3A4 substrates with a narrow therapeutic index. The dose of the sensitive CYP3A4 substrate with a narrow therapeutic index may need to be reduced.(5) The manufacturer of sirolimus states that the concurrent use of strong CYP3A4 inhibitors is not recommended and should be avoided.(1) The US manufacturer of temsirolimus recommends that concurrent therapy with strong CYP3A4 inhibitors such as ribociclib be avoided. If concurrent use is warranted, a dosage reduction to 12.5 mg/week of temsirolimus should be considered. If ribociclib is discontinued, a washout period of 1 week should be allowed before adjusting the dosage of temsirolimus to previous levels.(2)

DISCUSSION: In a study in healthy subjects, concomitant administration of ribociclib (400 mg once daily for 8 days) with midazolam increased the midazolam maximum concentration (Cmax) and area under the curve (AUC) by 2.1-fold and 3.8-fold, respectively. Administration of ribociclib 600 mg once daily is predicted to increase the midazolam Cmax and AUC by 2.4-fold and 5.2-fold, respectively.(5) Strong CYP3A4 inhibitors linked include: relacorilant and ribociclib.(6,7)

Cyclosporine;Tacrolimus/Baxdrostat; Potassium-Spar Diuretics

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Concurrent use of cyclosporine(1) or tacrolimus(2) with baxdrostat(3) or a potassium-sparing diuretic may result in additive or synergistic effects on potassium levels.

CLINICAL EFFECTS: Concurrent use of cyclosporine(1) or tacrolimus(2) with baxdrostat(3) or a potassium-sparing diuretic may result in severe hyperkalemia.

PREDISPOSING FACTORS: Renal impairment increases the risk for hyperkalemia.

PATIENT MANAGEMENT: The US manufacturers of cyclosporine(1) and tacrolimus(2) state that potassium-sparing diuretics should not be used during therapy with these agents.

DISCUSSION: Hyperkalemia has been reported with cyclosporine, therefore, the US manufacturer states that potassium-sparing diuretics should not be used with cyclosporine.(1) In tacrolimus clinical trials, mild to severe hyperkalemia was reported in 31% of kidney transplant patients, 45% of US liver transplant patients, and 13% of European liver transplant patients. The manufacturer of tacrolimus states that potassium levels should be closely monitored in all patients maintained on tacrolimus and that potassium-sparing diuretics should be avoided during tacrolimus therapy.(2)

Immunosuppres;Immunomodul/Selected Multiple Sclerosis Agents

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Ocrelizumab or ofatumumab in combination with immunosuppressives and immune-modulators all suppress the immune system.(1,2)

CLINICAL EFFECTS: Concurrent use of ocrelizumab or ofatumumab with immunosuppressive or immune-modulating agents may result in an increased risk of serious infections, such as disseminated herpetic infection or progressive multifocal leukoencephalopathy (PML), an opportunistic infection caused by the JC virus (JCV).(1,2)

PREDISPOSING FACTORS: Incomplete washout of previously prescribed immunosuppressive or immune-modulating medications.

PATIENT MANAGEMENT: The ocrelizumab US prescribing information states: - Ocrelizumab and other immune-modulating or immunosuppressive therapies, (including immunosuppressant doses of corticosteroids) are expected to increase the risk of immunosuppression, and the risk of additive immune system effects must be considered if these therapies are coadministered with ocrelizumab. When switching from drugs with prolonged immune effects, such as daclizumab, fingolimod, natalizumab, teriflunomide, or mitoxantrone, the duration and mode of action of these drugs must be considered to avoid unintended additive immunosuppressive effects when initiating ocrelizumab.(1) The ofatumumab US prescribing information states: - Ofatumumab and other immunosuppressive therapies (including systemic corticosteroids) may have the potential for increased immunosuppressive effects and increase the risk of infection. When switching between therapies, the duration and mechanism of action of each therapy should be considered due to the potential for additive immunosuppressive effects. Ofatumumab for MS therapy has not been studied in combination with other MS agents that suppress the immune system.(2)

DISCUSSION: Fatal disseminated herpes zoster and herpes simplex infections and cases of progressive multifocal leukoencephalopathy (PML) have been reported in patients who previously received immunomodulators or immunosuppressants.(1,2) In a retrospective cohort study of multiple sclerosis patients newly initiated on a disease-modifying therapy, use of high-efficacy agents (alemtuzumab, natalizumab, or ocrelizumab) resulted in the same risk of overall infections as moderate-efficacy agents, but there was an elevated risk of serious infections (adjusted hazard ratio [aHR] = 1.24, 95% confidence interval (CI) = 1.06-1.44) and UTIs (aHR = 1.21, 95% CI = 1.14-1.30).(3)

Immunosuppressives; Immunomodulators/Baricitinib

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Concurrent use of baricitinib with other biologic disease-modifying antirheumatic drugs (DMARDs) or potent immunosuppressants such as azathioprine or cyclosporine may result in additive or synergistic effects on the immune system.

CLINICAL EFFECTS: Concurrent use of baricitinib with other biologic DMARDs or potent immunosuppressants such as azathioprine or cyclosporine may increase the risk of serious infections.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of baricitinib states that concurrent use of baricitinib with biologic DMARDs or potent immunosuppressants is not recommended.(1)

DISCUSSION: Most patients who developed serious infections while being treated with baricitinib were on concomitant immunosuppressants like methotrexate and corticosteroids. The combination of baricitinib with other biologic DMARDs has not been studied.(1)

Immunosuppressives; Immunomodulators/Deuruxolitinib

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Deuruxolitinib, immunosuppressives, and immunomodulators all suppress the immune system.(1)

CLINICAL EFFECTS: Concurrent use of deuruxolitinib and potent immunosuppressants may increase the risk of serious infections.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of deuruxolitinib states that concurrent use of deuruxolitinib with other JAK inhibitors, biologic immunomodulators, cyclosporine or other potent immunosuppressants is not recommended.(1) If concurrent use cannot be avoided, patients should be monitored for signs and symptoms of infection. If a patient develops a serious or opportunistic infection, interrupt deuruxolitinib treatment until the infection is controlled.

DISCUSSION: Serious infections have been reported in patients receiving treatment with deuruxolitinib.(1)

Immunosuppressives; Immunomodulators/Etrasimod

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Etrasimod causes reversible sequestration of lymphocytes in lymphoid tissues, resulting in a mean 55% decrease in peripheral blood lymphocyte count at 52 weeks.(1) Other immunosuppressives and immune-modulators also suppress the immune system.

CLINICAL EFFECTS: Concurrent use of etrasimod with immunosuppressive or immune-modulating agents may result in an increased risk of serious and fatal infections, such as disseminated herpetic infection, cryptococcal infection, or progressive multifocal leukoencephalopathy (PML).(1)

PREDISPOSING FACTORS: Incomplete washout of previously prescribed immunosuppressive or immune-modulating medications increases the risk of adverse effects.

PATIENT MANAGEMENT: The etrasimod US prescribing information states etrasimod has not been studied in combination with anti-neoplastic, immune-modulating, or immunosuppressive therapies. Concomitant administration of these therapies with etrasimod should be avoided because of the risk of additive immune effects during therapy and in the weeks following administration. Etrasimod's effect on peripheral lymphocytes may persist for up to 5 weeks after discontinuation.(1) When switching from drugs with prolonged immune effects, the half-life and mode of action of these drugs must be considered in order to avoid unintended additive immunosuppressive effects.(1)

DISCUSSION: Fatal disseminated herpes zoster and herpes simplex infections, cryptococcal meningitis, disseminated cryptococcal infections, and cases of progressive multifocal leukoencephalopathy (PML) have been reported in patients treated with other sphingosine-1 phosphate receptor modulators.(1)

Immunosuppressives; Immunomodulators/Filgotinib

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Concurrent use of filgotinib with other immunosuppressants or immunomodulators including azathioprine, cyclosporine, tacrolimus, biologic disease-modifying antirheumatic drugs (DMARDs), or other Janus kinase (JAK) inhibitors may result in additive or synergistic effects on the immune system.(1)

CLINICAL EFFECTS: Concurrent use of filgotinib with other immunosuppressants or immunomodulators including azathioprine, cyclosporine, tacrolimus, biologic DMARDs, or other JAK inhibitors may increase the risk of serious infections.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The UK manufacturer of filgotinib states that concurrent use of filgotinib with other immunosuppressants or immunomodulators including azathioprine, cyclosporine, tacrolimus, biologic DMARDs, or other JAK inhibitors is not recommended.(1)

DISCUSSION: Serious infections have been reported in patients receiving filgotinib. Caution should be used in patients with a higher incidence of serious infection, including elderly patients aged 75 years and older.(1)

Immunosuppressives; Immunomodulators/Fingolimod

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Fingolimod in combination with immunosuppressives and immune-modulators all suppress the immune system.(1-3)

CLINICAL EFFECTS: Concurrent use of fingolimod with immunosuppressive or immune-modulating agents may result in an increased risk of serious infections, such as disseminated herpetic infection or progressive multifocal leukoencephalopathy (PML), an opportunistic infection caused by the JC virus (JCV).(1-3)

PREDISPOSING FACTORS: Incomplete washout of previously prescribed immunosuppressive or immune-modulating medications.

PATIENT MANAGEMENT: Recommendations for fingolimod regarding this interaction differ between regulatory approving agencies. The fingolimod US prescribing information states: - Antineoplastic, immune-modulating, or immunosuppressive therapies, (including corticosteroids) are expected to increase the risk of immunosuppression, and the risk of additive immune system effects must be considered if these therapies are coadministered with fingolimod. When switching from drugs with prolonged immune effects, such as natalizumab, teriflunomide or mitoxantrone, the duration and mode of action of these drugs must be considered to avoid unintended additive immunosuppressive effects when initiating fingolimod.(1) The fingolimod Canadian prescribing information states: - Concurrent use with immunosuppressive or immunomodulatory agents is contraindicated due to the risk of additive immune system effects. However, co-administration of a short course of corticosteroids (up to 5 days) did not increase the overall rate of infection in patients participating Phase III clinical trials.(2) The fingolimod UK specific product characteristics states: - Fingolimod is contraindicated in patients currently receiving immunosuppressive therapies or those immunocompromised by prior therapies. When switching patients from another disease modifying therapy to Gilenya, the half-life and mode of action of the other therapy must be considered in order to avoid an additive immune effect whilst at the same time minimizing the risk of disease activation.(3)

DISCUSSION: Fatal disseminated herpes zoster and herpes simplex infections and cases of progressive multifocal leukoencephalopathy (PML) have been reported in patients who previously received immunomodulators or immunosuppressants.(1-3)

Immunosuppressives; Immunomodulators/Inebilizumab

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Inebilizumab, immunosuppressives, and immunomodulators all suppress the immune system.(1)

CLINICAL EFFECTS: Concurrent use of inebilizumab with immunosuppressive or immunomodulating agents may result in myelosuppression including neutropenia resulting in an increased risk for serious infections.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of inebilizumab states that the concurrent use of inebilizumab with immunosuppressive agents, including systemic corticosteroids, may increase the risk of infection. If concurrent therapy is warranted, consider the risk of additive immune suppression and monitor based on prescribing information for both agents.(1)

DISCUSSION: Inebilizumab has not been studied in combination with other immunosuppressants. If concurrent therapy is warranted, consider the potential for increased immunosuppressive risks from both agents. The most common infections reported by inebilizumab treated patients in the randomized and open-label clinical trial periods included urinary tract infections (20%), nasopharyngitis (13%), upper respiratory tract infections (8%), and influenza (7%). Although there been no cases of Hepatitis B virus reactivation or progressive multifocal leukoencephalopathy reported in patients taking inebilizumab, these infections have been observed in patients taking other B-cell-depleting antibodies.(1)

Immunosuppressives; Immunomodulators/Ozanimod

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Ozanimod in combination with immunosuppressives and immune-modulators all suppress the immune system.(1)

CLINICAL EFFECTS: Concurrent use of ozanimod with immunosuppressive or immune-modulating agents may result in an increased risk of serious infections, such as disseminated herpetic infection or progressive multifocal leukoencephalopathy (PML), an opportunistic infection caused by the JC virus (JCV).(1)

PREDISPOSING FACTORS: Incomplete washout of previously prescribed immunosuppressive or immune-modulating medications.

PATIENT MANAGEMENT: The ozanimod US prescribing information state this information regarding this interaction: -Ozanimod has not been studied in combination with anti-neoplastic, immune-modulating, or immunosuppressive therapies. Caution should be used during concomitant administration because of the risk of additive immune effects during therapy and in the week following administration. When switching from drugs with prolonged immune effects, the half-life and mode of action of these drugs must be considered in order to avoid unintended additive immunosuppressive effects. Initiating treatment with ozanimod after alemtuzumab is not recommended. However, ozanimod can generally be started immediately after discontinuation of beta interferon or glatiramer acetate.(1)

DISCUSSION: Fatal disseminated herpes zoster and herpes simplex infections and cases of progressive multifocal leukoencephalopathy (PML) have been reported in patients who previously received immunomodulators or immunosuppressants.(1)

Immunosuppressives; Immunomodulators/Ponesimod

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Ponesimod in combination with immunosuppressives and immune-modulators all suppress the immune system.(1)

CLINICAL EFFECTS: Concurrent use of ponesimod with immunosuppressive or immune-modulating agents may result in an increased risk of serious infections, such as disseminated herpetic infection, cryptococcal infection, or progressive multifocal leukoencephalopathy (PML), an opportunistic infection caused by the JC virus (JCV).(1)

PREDISPOSING FACTORS: Incomplete washout of previously prescribed immunosuppressive or immune-modulating medications.

PATIENT MANAGEMENT: The ponesimod US prescribing information states ponesimod has not been studied in combination with anti-neoplastic, immune-modulating, or immunosuppressive therapies. Caution should be used during concomitant administration because of the risk of additive immune effects during therapy and in the weeks following administration. When switching from drugs with prolonged immune effects, the half-life and mode of action of these drugs must be considered in order to avoid unintended additive immunosuppressive effects. Initiating treatment with ponesimod after alemtuzumab is not recommended. However, ponesimod can generally be started immediately after discontinuation of beta interferon or glatiramer acetate.(1)

DISCUSSION: Fatal disseminated herpes zoster and herpes simplex infections, cryptococcal meningitis, disseminated cryptococcal infections, and cases of progressive multifocal leukoencephalopathy (PML) have been reported in patients who previously received immunomodulators or immunosuppressants.(1)

Immunosuppressives; Immunomodulators/Ritlecitinib

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Ritlecitinib, immunosuppressives, and immunomodulators all suppress the immune system.

CLINICAL EFFECTS: Concurrent use of ritlecitinib with immunosuppressives or immunomodulators may result in an increased risk of serious infections.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of ritlecitinib states that concurrent use of ritlecitinib with other JAK inhibitors, biologic immunomodulators, cyclosporine or other potent immunosuppressants is not recommended.(1)

DISCUSSION: Serious infections have been reported in patients receiving ritlecitinib. Reported infections included appendicitis, COVID-19 infection (including pneumonia), and sepsis. Reports of viral reactivation, including herpes virus reactivation was reported in clinical studies with ritlecitinib.(1)

Immunosuppressives; Immunomodulators/Siponimod

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Siponimod in combination with immunosuppressives and immune-modulators all suppress the immune system.(1)

CLINICAL EFFECTS: Concurrent use of siponimod with immunosuppressive or immune-modulating agents may result in an increased risk of serious infections, such as disseminated herpetic infection or progressive multifocal leukoencephalopathy (PML), an opportunistic infection caused by the JC virus (JCV).(1)

PREDISPOSING FACTORS: Incomplete washout of previously prescribed immunosuppressive or immune-modulating medications.

PATIENT MANAGEMENT: The siponimod US prescribing information state this information regarding this interaction: -Siponimod has not been studied in combination with anti-neoplastic, immune-modulating, or immunosuppressive therapies. Caution should be used during concomitant administration because of the risk of additive immune effects during therapy and in the week following administration. When switching from drugs with prolonged immune effects, the half-life and mode of action of these drugs must be considered in order to avoid unintended additive immunosuppressive effects. Initiating treatment with siponimod after alemtuzumab is not recommended. However, siponimod can generally be started immediately after discontinuation of beta interferon or glatiramer acetate.(1)

DISCUSSION: Fatal disseminated herpes zoster and herpes simplex infections and cases of progressive multifocal leukoencephalopathy (PML) have been reported in patients who previously received immunomodulators or immunosuppressants.(1)

Immunosuppressives; Immunomodulators/Tofacitinib

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Concurrent use of tofacitinib and azathioprine, other biologic disease-modifying antirheumatic drugs (DMARDs), or potent immunosuppressants may result in additive or synergistic effects on the immune system.(1)

CLINICAL EFFECTS: Concurrent use of tofacitinib and azathioprine, other biologic DMARDs, or potent immunosuppressants use may increase the risk of serious infections.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Tofacitinib should not be used concurrently with azathioprine, other biologic DMARDs, or cyclosporine.(1) Patient should be monitored for decreases in lymphocytes and neutrophils. Therapy should be adjusted based on the indication. - For all indications: If absolute neutrophil count (ANC) or lymphocyte count is less than 500 cells/mm3, discontinue tofacitinib. - For rheumatoid arthritis or psoriatic arthritis and absolute neutrophil count (ANC) 500 to 1000 cells/mm3: interrupt dosing. When ANC is greater than 1000 cells/mm3, resume Xeljanz 5 mg twice daily or Xeljanz XR 11 mg once daily. - For ulcerative colitis and ANC 500 to 1000 cells/mm3: -If taking Xeljanz 10 mg twice daily, decrease to 5 mg twice daily. When ANC is greater than 1000 cells/mm3, increase to 10 mg twice daily based on clinical response. -If taking Xeljanz 5 mg twice daily, interrupt dosing. When ANC is greater than 1000 cells/mm3, resume 5 mg twice daily. -If taking Xeljanz XR 22 mg once daily, decrease to 11 mg once daily. When ANC is greater than 1000 cells/mm3, increase to 22 mg once daily based on clinical response. -If taking Xeljanz XR 11 mg once daily, interrupt dosing. When ANC is greater than 1000 cells/mm3, resume 11 mg once daily. - For polyarticular course juvenile idiopathic arthritis (pcJIA) and ANC 500 to 1000 cells/mm3: interrupt dosing until ANC is greater than 1000 cells/mm3.(1)

DISCUSSION: Concurrent use of tofacitinib and azathioprine, other biologic DMARDs, or potent immunosuppressants may increase the risk of infection.(1) Serious infections due to bacterial, mycobacterial, invasive fungal, viral, or other opportunistic pathogens have been reported in patients receiving tofacitinib. Some patients presented with disseminated disease and were often taking concomitant immunomodulating agents. In the ulcerative colitis population, a greater risk of serious infections was seen with a higher tofacitinib dose. In 7 placebo-controlled rheumatoid arthritis trials (0-3 months exposure), the overall frequency of infections was 20% in the tofacitinib 5 mg twice daily group and 22% in the tofacitinib 10 mg twice daily group compared to 18% in the placebo group. Serious infections were reported in 11 patients (1.7 events per 100 patient-years) with a rate difference between treatment groups of 1.1 (-0.4, 2.5) events per 100 patient-years for both tofacitinib 5 mg twice daily and 10 mg twice daily. During 0-12 months exposure, serious infections were reported in 34 patients (2.7 events per 100 patient years) in the tofacitinib 5 mg twice daily group and 33 patients (2.7 events per 100 patient years) in the tofacitinib 10 mg twice daily group.(1)

Immunosuppressives; Immunomodulators/Upadacitinib

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Upadacitinib, immunosuppressives, and immunomodulators all suppress the immune system.

CLINICAL EFFECTS: Concurrent use of upadacitinib with immunosuppressives or immunomodulators may result in an increased risk of serious infections.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of upadacitinib states that concurrent use of upadacitinib with immunosuppressives or immunomodulators is not recommended.

DISCUSSION: Serious infections have been reported in patients receiving upadacitinib. Reported infections included pneumonia, cellulitis, tuberculosis, multidermatomal herpes zoster, oral/esophageal candidiasis, cryptococcosis. Reports of viral reactivation, including herpes virus reactivation and hepatitis B reactivation, were reported in clinical studies with upadacitinib.(1)

Myelosuppressives; Immunomodulators/Sodium Iodide I 131

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Sodium iodide I 131 can cause depression of the hematopoetic system. Myelosuppressives and immunomodulators also suppress the immune system.(1)

CLINICAL EFFECTS: Concurrent use of sodium iodide I 131 with agents that cause bone marrow depression, including myelosuppressives or immunomodulators, may result in an enhanced risk of hematologic disorders, including anemia, blood dyscrasias, bone marrow depression, leukopenia, and thrombocytopenia. Bone marrow depression may increase the risk of serious infections and bleeding.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of sodium iodide I 131 states that concurrent use with bone marrow depressants may enhance the depression of the hematopoetic system caused by large doses of sodium iodide I 131.(1) Sodium iodide I 131 causes a dose-dependent bone marrow suppression, including neutropenia or thrombocytopenia, in the 3 to 5 weeks following administration. Patients may be at increased risk of infections or bleeding during this time. Monitor complete blood counts within one month of therapy. If results indicate leukopenia or thrombocytopenia, dosimetry should be used to determine a safe sodium iodide I 131 activity.(1)

DISCUSSION: Hematologic disorders including death have been reported with sodium iodide I 131. The most common hematologic disorders reported include anemia, blood dyscrasias, bone marrow depression, leukopenia, and thrombocytopenia.(1)

Oatp1b1 Inhibitors/Eluxadoline

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: OATP1B1 inhibitors may decrease the hepatic uptake of eluxadoline.(1)

CLINICAL EFFECTS: Concurrent use of OATP1B1 inhibitors may result in elevated levels of and side effects from eluxadoline, including constipation, nausea, abdominal pain, and impaired mental and physical abilities.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Patients receiving concurrent OATP1B1 inhibitors should receive a dose of eluxadoline of 75 mg twice daily. Monitor patients for impaired mental or physical abilities, abdominal pain, nausea, and constipation.(1)

DISCUSSION: Concurrent administration of a single dose (600 mg) of cyclosporine, an OATP1B1 inhibitor, increased the maximum concentration (Cmax) and area-under-curve (AUC) of a single dose of eluxadoline (100 mg) by 4.4-fold and 6.2-fold, respectively.(1) OATP1B1 inhibitors include: atazanavir, belumosudil, boceprevir, cyclosporine, darunavir, encorafenib, eltrombopag, erythromycin, gemfibrozil, leflunomide, leniolisib, letermovir, lopinavir, paritaprevir, resmetirom, rifampin, ritonavir, roxadustat, saquinavir, simeprevir, telaprevir, teriflunomide, tipranavir, vadadustat, and voclosporin.(1,2)

Oatp1b1-3 Inhibitors/Brincidofovir

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: OATP1B1 and 1B3 inhibitors may increase the absorption and/or decrease the hepatic uptake of brincidofovir.(1)

CLINICAL EFFECTS: Concurrent use of OATP1B1 or 1B3 inhibitors may result in elevated levels of and side effects from brincidofovir.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of brincidofovir states that alternative medications that are not OATP1B1 or 1B3 inhibitors should be considered. If concurrent use is necessary, instruct the patient to take the OATP1B1 or 1B3 inhibitor at least 3 hours after brincidofovir and increase monitoring for side effects, including transaminase and bilirubin elevations and GI side effects like diarrhea.(1)

DISCUSSION: In a clinical trial, single-dose oral cyclosporine (600 mg, an OATP1B1 and 1B3 inhibitor) increased the mean brincidofovir area-under-curve (AUC) and maximum concentration (Cmax) by 374% and 269%, respectively.(1) OATP1B1 and 1B3 inhibitors include: atazanavir, belumosudil, boceprevir, clarithromycin, cyclosporine, darunavir, eltrombopag, encorafenib, erythromycin, gemfibrozil, glecaprevir-pibrentasvir, ledipasvir, leflunomide, leniolisib, letermovir, lopinavir, ombitasvir-paritaprevir, paritaprevir, resmetirom, rifampin, ritonavir, roxadustat, saquinavir, simeprevir, sofosbuvir, telaprevir, teriflunomide, tipranavir, vadadustat, velpatasvir, and voclosporin.(1,2)

P-Glycoprotein (P-GP) Inhibitors/Bilastine

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: P-glycoprotein (P-gp) inhibition may increase the absorption of bilastine.(1,2)

CLINICAL EFFECTS: Concurrent use of P-gp inhibitors may result in elevated levels and toxicities from bilastine, including headache and somnolence.(1,2)

PREDISPOSING FACTORS: The interaction magnitude may be greater in patients with moderate to severe renal impairment.

PATIENT MANAGEMENT: The Canadian manufacturer of bilastine states that concomitant use of P-gp inhibitors with bilastine is not recommended. Coadministration should be avoided in patients with moderate or severe renal impairment.(1) The UK manufacturer of bilastine states that coadministration of bilastine and P-gp inhibitors should be avoided in patients with moderate to severe renal impairment.(2) The manufacturer of daraxonrasib states P-gp substrates should be administered at least 4 hours apart from daraxonrasib.(5)

DISCUSSION: In a study, ketoconazole and erythromycin both increased bilastine area-under-curve (AUC) and maximum concentration (Cmax) by 2-fold and 2- to 3-fold, respectively.(1) The UK manufacturer of bilastine states that these changes do not appear to affect the safety of bilastine.(2) P-gp inhibitors linked to this monograph include: amiodarone, asunaprevir, aumolertinib, azithromycin, belumosudil, capmatinib, carvedilol, cimetidine, cyclosporine, daclatasvir, danicopan, daraxonrasib, daridorexant, deutivacaftor, diltiazem, diosmin, dronedarone, eliglustat, erythromycin, flibanserin, fluvoxamine, fostamatinib, ginkgo, ginseng, glecaprevir/pibrentasvir, hydroquinidine, imlunestrant, istradefylline, ivacaftor, lapatinib, ledipasvir, mavorixafor, neratinib, osimertinib, paroxetine, pirtobrutinib, posaconazole, propafenone, quercetin, quinidine, quinine, ranolazine, sarecycline, schisandra, selpercatinib, simeprevir, sofosbuvir/velpatasvir/voxilaprevir, sotorasib, tepotinib, valbenazine, vemurafenib, vepdegestrant, verapamil, vimseltinib, and voclosporin.(4,5)

P-Glycoprotein (P-GP) Inhibitors/Pralsetinib

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: P-glycoprotein (P-gp) inhibitors may inhibit cellular efflux of pralsetinib.(1)

CLINICAL EFFECTS: Concurrent administration of a P-gp inhibitor may result in elevated levels of and toxicity from pralsetinib, including hemorrhagic events, pneumonitis, hepatotoxicity, hypertension, and QTc prolongation, which may result in potentially life-threatening cardiac arrhythmias like torsades de pointes (TdP).(1-3)

PREDISPOSING FACTORS: The risk of QT prolongation or torsades de pointes may be increased in patients with cardiovascular disease (e.g. heart failure, myocardial infarction, history of torsades de pointes, congenital long QT syndrome), hypokalemia, hypomagnesemia, hypocalcemia, bradycardia, female gender, or advanced age.(4) Concurrent use of more than one drug known to cause QT prolongation or higher systemic concentrations of either QT prolonging drug are additional risk factors for torsades de pointes. Factors which may increase systemic drug concentrations include rapid infusion of an intravenous dose or impaired metabolism or elimination of the drug (e.g. coadministration with an agent which inhibits its metabolism or elimination, genetic impairment in drug metabolism or elimination, and/or renal/hepatic dysfunction).(4)

PATIENT MANAGEMENT: Coadministration of pralsetinib with a P-gp inhibitor should be avoided.(1) If coadministration with a P-gp inhibitor cannot be avoided, use with caution and reduce the dose of pralsetinib as follows: -If the current dose is 400 mg once daily, decrease the dose to 300 mg daily. -If the current dose is 300 mg once daily, decrease the dose to 200 mg daily. -If the current dose is 200 mg once daily, decrease the dose to 100 mg daily. After the inhibitor is discontinued for three to five half-lives, resume the dose of pralsetinib at the dose taken prior to initiation of the inhibitor.(1) The manufacturer of venetoclax states that if concurrent use with a P-gp substrate cannot be avoided, take pralsetinib at least 6 hours before venetoclax.(5) The manufacturer of daraxonrasib states P-gp substrates should be administered at least 4 hours apart from daraxonrasib.(8) When concurrent therapy is warranted: consider obtaining serum calcium, magnesium, and potassium levels and monitoring EKG at baseline and regular intervals. Correct any electrolyte abnormalities. Instruct patients to report any irregular heartbeat, dizziness, or fainting. If the QTc interval exceeds 500 ms, interrupt pralsetinib therapy until QTc is <470 ms. Resume pralsetinib at the same dose if risk factors that cause QT prolongation an are identified and corrected. If risk factors that cause QT prolongation are not identified, resume pralsetinib at a reduced dose. Permanently discontinue pralsetinib if the patient develops life-threatening arrhythmia.(3)

DISCUSSION: Coadministration of a single dose of cyclosporine 600 mg (a P-gp inhibitor) with a single pralsetinib 200 mg dose increased pralsetinib concentration maximum (Cmax) by 48% and area-under-curve (AUC) by 81%.(1) P-glycoprotein inhibitors linked to this monograph include: asunaprevir, belumosudil, carvedilol, cyclosporine, danicopan, daraxonrasib, daridorexant, deutivacaftor, diosmin, flibanserin, fostamatinib, ginseng, glecaprevir/pibrentasvir, ivacaftor, ledipasvir, neratinib, sofosbuvir/velpatasvir/voxilaprevir, tepotinib, valbenazine, venetoclax, vimseltinib, and voclosporin.(6,7)

P-Glycoprotein (P-GP) Inhibitors/Relugolix

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Relugolix is a substrate of the intestinal P-glycoprotein (P-gp) efflux transporter. Inhibitors of P-gp may increase the absorption of relugolix.(1)

CLINICAL EFFECTS: The concurrent administration of relugolix with an inhibitor of P-glycoprotein may result in elevated levels of relugolix and adverse effects, including hot flashes, skin flushing, musculoskeletal pain, hyperglycemia, acute renal injury, transaminitis, arrhythmias, and hemorrhage.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of relugolix states that the coadministration of relugolix with P-gp inhibitors should be avoided. If the P-gp inhibitor is to be used short-term, relugolix may be held for up to 2 weeks. If treatment with relugolix is interrupted for longer than 7 days, resume relugolix with a loading dose of 360 mg on the first day, followed by 120 mg once daily.(1) If coadministration with a P-gp inhibitor cannot be avoided, relugolix should be taken at least 6 hours before the P-gp inhibitor. Monitor the patient more frequently for adverse events.(1) For patients on daraxonrasib, the manufacturer of daraxonrasib states that it should be taken at least 4 hours apart from P-gp substrates.(2)

DISCUSSION: Coadministration of relugolix with erythromycin (a P-gp and moderate CYP3A4 inhibitor) increased the area-under-curve (AUC) and maximum concentration (Cmax) of relugolix by 6.2-fold. Voriconazole (a strong CYP3A4 inhibitor) did not have a clinically significant effect on the pharmacokinetics of relugolix.(1) P-gp inhibitors linked to this monograph include: amiodarone, asunaprevir, aumolertinib, azithromycin, belumosudil, capmatinib, carvedilol, cimetidine, clarithromycin, cobicistat, conivaptan, curcumin, cyclosporine, daclatasvir, danicopan, daraxonrasib, daridorexant, deutivacaftor, diltiazem, diosmin, dronedarone, eliglustat, erythromycin, flibanserin, fluvoxamine, fostamatinib, ginkgo, ginseng, glecaprevir/pibrentasvir, indinavir, itraconazole, ivacaftor, josamycin, ketoconazole, lapatinib, lonafarnib, mavorixafor, mibefradil, mifepristone, neratinib, osimertinib, paroxetine, pirtobrutinib, posaconazole, propafenone, quinidine, quinine, ranolazine, ritonavir, sarecycline, schisandra, selpercatinib, simeprevir, sotorasib, telaprevir, telithromycin, tepotinib, tucatinib, valbenazine, velpatasvir, vemurafenib, venetoclax, vepdegestrant, verapamil, vimseltinib, and voclosporin.(3,4)

P-Glycoprotein (P-GP) Inhibitors/Vincristine

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: P-glycoprotein (P-gp) inhibitors may inhibit cellular efflux of vincristine.(1)

CLINICAL EFFECTS: Concurrent administration of a P-gp inhibitor may result in elevated levels of and toxicity from vincristine including myelosuppression, neurologic toxicity, tumor lysis syndrome, hepatotoxicity, constipation, or bowel obstruction.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Avoid the use of P-gp inhibitors in patients undergoing therapy with vincristine.(1) Consider alternatives with no or minimal P-gp inhibition. The manufacturer of vincristine states that concomitant use of P-gp inhibitors should be avoided.(1) The manufacturer of lopinavir/ritonavir states that patients who develop significant hematological or gastrointestinal toxicity on concomitant vincristine should temporarily hold lopinavir/ritonavir, or use alternative medications that do not inhibit CYP3A4 or P-gp.(2) The manufacturer of daraxonrasib states that it should be taken at least 4 hours apart from P-gp substrates.(3)

DISCUSSION: Vincristine is a substrate of P-gp. Inhibitors of P-gp may increase toxicity of vincristine.(1) There are several case reports of neurotoxicity with concurrent administration of vincristine and itraconazole.(4-6) There is a case report of neurotoxicity with concurrent administration of lopinavir-ritonavir with vincristine.(7) In a prospective study in 22 children receiving various chemotherapy with prophylactic itraconazole oral solution (0.5 ml/kg per day), two children receiving vincristine developed non-alcoholic steatohepatitis (NASH) and one child developed syndrome of inappropriate anti-diuretic hormone secretion (SIADH).(8) Inhibitors of P-gp linked to this monograph include: abrocitinib, amiodarone, Asian ginseng (Panax ginseng), asunaprevir, aumolertinib, azithromycin, belumosudil, capmatinib, carvedilol, cimetidine, cyclosporine, danicopan, daraxonrasib, daridorexant, deutivacaftor, diltiazem, diosmin, dronedarone, elagolix, eliglustat, erythromycin, flibanserin, fluvoxamine, fostamatinib, ginkgo biloba, glecaprevir and pibrentasvir, imlunestrant, isavuconazonium, ivacaftor, lapatinib, mavorixafor, milk thistle (Silybum marianum), neratinib, osimertinib, pirtobrutinib, propafenone, quercetin, quinidine, ranolazine, rolapitant, Schisandra chinensis, selpercatinib, sofosbuvir, sotorasib, tepotinib, valbenazine, velpatasvir, vemurafenib, venetoclax, vepdegestrant, verapamil, vilazodone, vimseltinib, and voclosporin.(9-10)

Selected Cyp3a4 Inhibitor/Tolterodine (>1 MG IR OR >2 MG ER)

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Cyclosporine, erythromycin, miconazole, and vinblastine may inhibit the metabolism of tolterodine by CYP3A4.(1,2)

CLINICAL EFFECTS: The concurrent administration of tolterodine with cyclosporine, erythromycin, miconazole, or vinblastine may result in elevated levels of tolterodine and signs of toxicity.(1,2)

PREDISPOSING FACTORS: Patients who are CYP2D6 poor metabolizers may be at increased risk.(1,2) The risk of QT prolongation or torsades de pointes may be increased in patients with cardiovascular disease (e.g. heart failure, myocardial infarction, history of torsades de pointes, congenital long QT syndrome), hypokalemia, hypomagnesemia, hypocalcemia, bradycardia, female gender, or advanced age.(3) Concurrent use of more than one drug known to cause QT prolongation or higher systemic concentrations of either QT prolonging drug are additional risk factors for torsades de pointes. Factors which may increase systemic drug concentrations include rapid infusion of an intravenous dose or impaired metabolism or elimination of the drug (e.g. coadministration with an agent which inhibits its metabolism or elimination, genetic impairment in drug metabolism or elimination, and/or renal/hepatic dysfunction).(3) The risk of anticholinergic toxicities including cognitive decline, delirium, falls and fractures is increased in geriatric patients using more than one medicine with anticholinergic properties.(4)

PATIENT MANAGEMENT: The manufacturer of tolterodine recommends that a maximum tolterodine dosage of 1 mg twice daily of the non extended release dosage form(1) or 2 mg once daily of the extended release dosage form(2) be used in patients receiving concurrent therapy with cyclosporine, erythromycin, miconazole, or vinblastine. If concurrent therapy is warranted, consider obtaining serum calcium, magnesium, and potassium levels and monitoring ECG at baseline and at regular intervals. Correct any electrolyte abnormalities. Instruct patients to report any irregular heartbeat, dizziness, or fainting.

DISCUSSION: In a study in eight subjects who were deficient in CYP2D6, the concurrent administration of tolterodine (2 mg) with ketoconazole (200 mg once daily for four days), another inhibitor of CYP3A4, resulted in a 60% decrease in tolterodine clearance.(5) Tolterodine AUC and Cmax increased 2.5-fold and 2-fold, respectively.(2) In a study of the effect of tolterodine immediate release tablets, the effect on the QT interval appeared greater for 8 mg/day (two times the therapeutic dose) compared to 4 mg/day. Tolterodine 2 mg BID and tolterodine 4 mg BID increased the QTcF by 5.01 msec (0.28-9.74 msec) and 11.84 msec (7.11-16.58 msec), respectively. The change in QT interval was more pronounced in CYP2D6 poor metabolizers (PM) than extensive metabolizers (EMs).(1,2)

Selected Cyp3a4 Substrates/Ceritinib

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Ceritinib inhibits CYP3A4, and thus may inhibit the metabolism of agents processed by this isoenzyme.(1)

CLINICAL EFFECTS: Concurrent use of ceritinib with drugs primarily metabolized by CYP3A4 may lead to elevated drug levels and increased side effects of these agents. Drugs with a narrow therapeutic window that are metabolized by this isoenzyme include: cyclosporine, felodipine, hydroquinidine, midazolam, nisoldipine, quinidine, and sirolimus.(1,2)

PREDISPOSING FACTORS: Greater risk for adverse events would be expected for drugs with a narrow therapeutic window, or for drugs especially sensitive to CYP3A4 inhibition. With pimozide, the risk of anticholinergic toxicities including cognitive decline, delirium, falls and fractures is increased in geriatric patients using more than one medicine with anticholinergic properties.(4)

PATIENT MANAGEMENT: Avoid coadministration of sensitive CYP3A4 substrates with a narrow therapeutic index. If concomitant use is unavoidable, dosage adjustment of the CYP3A4 substrate should be considered when initiating or discontinuing ceritinib.(1) Patients maintained on ceritinib may need lower initial doses of the CYP3A4 substrate. Monitor patients receiving concurrent therapy for adverse effects.

DISCUSSION: In a study, ceritinib (750 mg daily for 3 weeks) increased the area-under-curve (AUC) and maximum concentration (Cmax) of midazolam (a CYP3A4 substrate) by 5.4-fold and 1.8-fold, respectively, compared to midazolam alone.(1) Thus, ceritinib is expected to increase levels of cyclosporine, felodipine, hydroquinidine, midazolam, nisoldipine, quinidine, and sirolimus.

Selected Cyp3a4 Substrates/Crizotinib

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Crizotinib inhibits CYP3A4, and thus may inhibit the metabolism of agents processed by this isoenzyme.(1)

CLINICAL EFFECTS: Concurrent use of crizotinib with drugs primarily metabolized by CYP3A4 may lead to elevated drug levels and increased side effects of these agents.(1) Drugs with a narrow therapeutic window that are metabolized by this isoenzyme include: abemaciclib, cisapride, cyclosporine, felodipine, hydroquinidine, lovastatin, midazolam, nisoldipine, quinidine, simvastatin, and sirolimus.(1-2)

PREDISPOSING FACTORS: Greater risk for adverse events would be expected for drugs with a narrow therapeutic window, or for drugs especially sensitive to CYP3A4 inhibition.

PATIENT MANAGEMENT: Avoid coadministration of sensitive CYP3A4 substrates with a narrow therapeutic index. If concomitant use is unavoidable, dosage adjustment of the CYP3A4 substrate should be considered when initiating or discontinuing crizotinib.(1) Patients maintained on crizotinib may need lower initial doses of the CYP3A4 substrate. Monitor patients receiving concurrent therapy for adverse effects. Drug-specific recommendations: The manufacturer of abemaciclib recommends monitoring for adverse reactions and considering a dose reduction of abemaciclib in 50 mg decrements as detailed in prescribing information (based on starting dose, previous dose reductions, and combination or monotherapy use) with concurrent use of moderate CYP3A4 inhibitors.(3)

DISCUSSION: Crizotinib (250 mg twice daily for 28 days) increased the area-under-curve (AUC) of oral midazolam by 3.7-fold.(1) Thus, crizotinib is expected to increase levels of abemaciclib, cisapride, cyclosporine, felodipine, hydroquinidine, lovastatin, midazolam, nisoldipine, quinidine, and simvastatin.

Selected Cyp3a4 Substrates/Mitapivat

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Mitapivat is a moderate inducer of CYP3A4 and may increase the metabolism of drugs metabolized by the CYP3A4 enzyme.

CLINICAL EFFECTS: Concurrent use of mitapivat may lead to decreased serum levels and effectiveness of drugs metabolized by the CYP3A4 pathway.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: When mitapivat is used for the treatment of hemolytic anemia in patients with pyruvate kinase deficiency, the US manufacturer of mitapivat states that co-administration of CYP3A4 substrates for which minimal concentration decreases may lead to serious therapeutic failure should be monitored for loss of efficacy. If concomitant use is unavoidable, increase the dose of the CYP3A4 substrate in accordance with approved product labeling.(1) When mitapivat is used for the treatment of anemia in patients with alpha- or beta-thalassemia, the US manufacturer of mitapivat states that coadministration of sensitive CYP3A4 substrates with narrow therapeutic indices should be avoided.(2) The Middle Weatern manufacturer of mitapivat states that alternative agents should be considered or the coadministered CYP3A4 substrate should be monitored for loss of efficacy.(3)

DISCUSSION: In a clinical study, coadministration of mitapivat 5 mg twice daily with midazolam, a sensitive CYP3A4 substrate, decreased midazolam area-under-curve (AUC) and maximum concentration (Cmax) by 21% and 19%, respectively. Midazolam AUC and Cmax were decreased by 43% and 39%, respectively with mitapivat 20 mg twice daily by 57% and 32%, respectively with mitapivat 50 mg twice daily, and by 65% and 59%, respectively with mitapivat 100 mg twice daily.(1) CYP3A4 substrates with a narrow therapeutic index linked to this monograph include: cyclosporine, everolimus, sirolimus, tacrolimus, and temsirolimus.(4-9)

Selected Immunosuppressants/Chloramphenicol

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: The mechanism by which chloramphenicol increases the levels of cyclosporine, everolimus, sirolimus, tacrolimus, and temsirolimus is unknown. Postulated mechanisms include chloramphenicol inhibition of the CYP3A4 metabolism of the immunosuppressive agents, or chloramphenicol inhibition of efflux transporters (e.g., p-glycoprotein).(1-3)

CLINICAL EFFECTS: Concurrent administration of chloramphenicol may result in elevated levels of and toxicity from cyclosporine, everolimus, sirolimus, tacrolimus, or temsirolimus.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The American Society of Transplantation guidelines recommend lowering the dose of cyclosporine or tacrolimus by 25% and close monitoring of immunosuppressive levels.(1) Although there are no specific recommendations for everolimus or sirolimus, it is expected that a similar interaction would occur and that management would be similar. The US manufacturer of tacrolimus states that coadministration with chloramphenicol may result in a rapid and sharp rise in tacrolimus concentration despite immediate tacrolimus dose reduction. Frequent monitoring of tacrolimus levels should start within 1-3 days of initiation of concurrent therapy and continue as necessary.(2)

DISCUSSION: A retrospective study of 6 kidney transplant patients (3 on cyclosporine and 3 on tacrolimus) who were given chloramphenicol found that cyclosporine troughs increased by a mean of 41.3 %, and tacrolimus troughs increased by a mean of 207 %, compared to levels prior to starting chloramphenicol.(3) Case reports have described highly variable effects of chloramphenicol on drug concentrations of immunosuppressants. One case of an interaction with cyclosporine described an increase in cyclosporine concentrations of 186 %, whereas another case described an increase of 300-850 %, but interpretation of this effect is complicated by the patient's therapy with rifampin just prior to chloramphenicol.(3,4) In other case reports, tacrolimus AUC increased 7.5-fold in one patient,(5) tacrolimus trough increased 5-fold in another patient who received an overdose of chloramphenicol,(6) and tacrolimus trough increased 3-fold in a third patient.(7)

Selected Immunosuppressants/Idelalisib

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Idelalisib increases plasma levels of cyclosporine, sirolimus, and temsirolimus by inhibition on CYP3A4.(1-3)

CLINICAL EFFECTS: Concurrent idelalisib may result in elevated levels of and toxicity from cyclosporine, sirolimus, and temsirolimus.(1-3)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Cyclosporine, sirolimus, or temsirolimus levels and renal function should be monitored if idelalisib is initiated or discontinued from concurrent therapy. The dosage of cyclosporine, sirolimus, or temsirolimus may need to be adjusted. The US manufacturer of sirolimus recommends that concurrent therapy with strong CYP3A4 inhibitors such as idelalisib by avoided. Alternative agents with lesser interaction potential with sirolimus should be considered.(2) The US manufacturer of temsirolimus recommends that concurrent therapy with strong CYP3A4 inhibitors such as idelalisib be avoided. If concurrent use is warranted, a dosage reduction to 12.5 mg/week of temsirolimus should be considered. If idelalisib is discontinued, a washout period of 1 week should be allowed before adjusting the dosage of temsirolimus to previous levels.(3)

DISCUSSION: Multiple-dose ketoconazole, another inhibitor of CYP3A4, administration significantly affected the rate and extent of absorption and sirolimus exposure after administration of sirolimus oral solution, as reflected by increases in sirolimus concentration maximum (Cmax), time maximum (tmax), and area-under-curve (AUC) of 4.3-fold, 38%, and 10.9-fold, respectively. However, the terminal half-life of sirolimus was not changed. Single-dose sirolimus did not affect steady-state 12-hour plasma ketoconazole concentrations.(2) Concurrent administration of ketoconazole, another inhibitor of CYP3A4, had no effects on temsirolimus AUC or Cmax; however, sirolimus AUC and Cmax increased 3.1-fold and 2.2-fold, respectively. Dosage adjustment of temsirolimus to 12.5 mg/week in the presence of strong CYP3A4 inhibitors is expected to adjust levels to the range observed without inhibitors; however, there are no data available with this dose adjustment.(3)

Selected Immunosuppressants/Leflunomide; Teriflunomide

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Concurrent use of leflunomide or teriflunomide and potent immunosuppressants may result in additive or synergistic effects on the immune system.(1,2) Leflunomide is a prodrug and is converted to its active metabolite teriflunomide.(1)

CLINICAL EFFECTS: Concurrent use of leflunomide or teriflunomide with immunosuppressants may result in an increased risk of serious infections, including opportunistic infections, especially Pneumocystis jiroveci pneumonia, tuberculosis (including extra-pulmonary tuberculosis), and aspergillosis.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: If leflunomide or teriflunomide is used concurrently with immunosuppressive agents, chronic CBC monitoring should be performed more frequently, every month instead of every 6 to 8 weeks. If bone marrow suppression or a serious infection occurs, leflunomide or teriflunomide should be stopped and rapid drug elimination procedure should be performed.(1,2)

DISCUSSION: Pancytopenia, agranulocytosis and thrombocytopenia have been reported in patients receiving leflunomide or teriflunomide alone, but most frequently in patients taking concurrent immunosuppressants.(1,2) Severe and potentially fatal infections, including sepsis, have been reported in patients receiving leflunomide or teriflunomide, especially Pneumocystis jiroveci pneumonia and aspergillosis. Tuberculosis has also been reported.(1,2)

Selected Immunosuppressants/Levoketoconazole

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: The metabolism of cyclosporine, sirolimus, and temsirolimus by CYP3A4 may be inhibited by levoketoconazole.

CLINICAL EFFECTS: Concurrent administration of levoketoconazole may result in elevated levels of and toxicity from cyclosporine, sirolimus, or temsirolimus.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Cyclosporine, sirolimus, or temsirolimus levels and renal function should be monitored if levoketoconazole is initiated or discontinued from concurrent therapy. The dosage of cyclosporine, sirolimus, or temsirolimus may need to be adjusted. The US manufacturer of temsirolimus recommends that concurrent therapy with strong CYP3A4 inhibitors such as levoketoconazole be avoided. If concurrent use is warranted, a dosage reduction to 12.5 mg/week of temsirolimus should be considered. If levoketoconazole is discontinued, a washout period of 1 week should be allowed before adjusting the dosage of temsirolimus to previous levels. The US manufacturer of sirolimus protein-bound injection (Fyarro) states concurrent use with strong CYP3A4 inhibitors should be avoided. The US manufacturer of levoketoconazole states concurrent use with sensitive CYP3A4 substrates should be avoided.

DISCUSSION: Ketoconazole has been reported to increase cyclosporine concentrations . Exercise caution when stopping levoketoconazole as cyclosporine concentration may decrease. In a multiple-dose study, concomitant administration of ketoconazole with sirolimus oral solution increased the sirolimus Cmax, time to Cmax (Tmax), and AUC by 4.3-fold, 38%, and 10.9-fold, respectively. Single-dose sirolimus did not affect steady-state 12-hour plasma ketoconazole concentrations. In a study in 6 patients, ketoconazole was successfully used to augment sirolimus levels. Patients were able to receive one-eight to one-fourth (0.25 - 0.50 mg daily) of the usual sirolimus dose while taking 100 to 200 mg of ketoconazole daily. Concurrent administration of ketoconazole had no effects on temsirolimus AUC or Cmax; however, sirolimus AUC and Cmax increased 3.1-fold and 2.2-fold, respectively. Dosage adjustment of temsirolimus to 12.5 mg/week in the presence of strong CYP3A4 inhibitors is expected to adjust levels to the range observed without inhibitors; however, there are no data available with this dose adjustment.

Selected Immunosuppressants/Nsaids; Salicylates

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Cyclosporine increases the production of prostaglandin E2 and I2. Prostaglandin E2 has been shown to prevent cyclosporine -induced renal toxicity in animals. NSAIDS and salicylates may increase cyclosporine-induced renal toxicity by blocking the formation of prostaglandins. Concurrent use of everolimus, sirolimus or tacrolimus with NSAIDs or salicylates may result in additive nephrotoxicity.

CLINICAL EFFECTS: Concurrent administration of cyclosporine, everolimus, sirolimus, or tacrolimus and a NSAID or salicylate may result in a decrease in renal function, with or without an alteration in immunosuppressant levels.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: If possible, avoid the concurrent use of NSAIDs or salicylates in patients maintained on cyclosporine, everolimus, sirolimus, or tacrolimus. If concurrent therapy is warranted, patients should be monitored for a decrease in renal function. The NSAID or salicylate may need to be discontinued.

DISCUSSION: A decrease in renal function has been reported with concurrent cyclosporine and diclofenac, sulindac, mefenamic acid, ketoprofen, piroxicam, and naproxen. Decreasing the cyclosporine dose without discontinuing the NSAID does not appear to improve renal function. The use of agents which decrease renal function concurrently with everolimus, sirolimus or tacrolimus should be approached with caution. An observational study of 63 inpatient encounters for 57 transplant patients evaluated concurrent use between calcineurin inhibitor (CNI) therapy and NSAID use. Patients were matched to 126 transplant patients on CNI therapy without NSAID use. Patients who received at least one dose of NSAID had a 12.2% rate of treatment emergent acute kidney injury (AKI). The relative risk ratio for AKI in patient exposed to NSAID therapy was 2.20 (95% CI 0.74-6.54). An increase in 48 hour post NSAID exposure serum creatinine above baseline was documented in 65.9% of patients compared to 46% in the non NSAID group (p=0.016). Multivariate analysis revealed changes in serum creatinine at 48 hours after admission were independently associated with age (p=0.008) and NSAID use (p=0.026).(12)

Selected Immunosuppressants/Posaconazole

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: The metabolism of cyclosporine and temsirolimus by CYP3A4 may be inhibited by posaconazole.(1-3)

CLINICAL EFFECTS: Concurrent administration of posaconazole may result in elevated levels of and toxicity from cyclosporine or temsirolimus.(1-3)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Cyclosporine or temsirolimus levels and renal function should be monitored if posaconazole is initiated or discontinued from concurrent therapy.(1-3) The US manufacturer of posaconazole recommends that the dose of cyclosporine be reduced by approximately 75% of the original dosage when posaconazole is initiated. Cyclosporine levels should be closely monitored during concurrent azole therapy. The dosage of cyclosporine may need adjusting when azole therapy has been completed.(1-2) The US manufacturer of temsirolimus recommends that concurrent therapy with strong CYP3A4 inhibitors be avoided. If concurrent use is warranted, a dosage reduction to 12.5 mg/week of temsirolimus should be considered. If the azole is discontinued, a washout period of 1 week should be allowed before adjusting the dosage of temsirolimus to previous levels.(3) Posaconazole tablets have improved bioavailability and higher concentrations per dose than posaconazole suspension. A greater dose reduction of the immunosuppressant may be necessary when posaconazole tablets are used.(4-6)

DISCUSSION: Concurrent use of posaconazole in heart transplant patients resulted in increased cyclosporine levels requiring dosage adjustments. In clinical trials, increased cyclosporine levels resulting in serious adverse events including nephrotoxicity, leukoencephalopathy, and death were reported. One study looked at the effects of posaconazole on the metabolism of cyclosporine when administered concurrently in heart transplant recipients. The study found when both medications were used concomitantly that cyclosporine exposure increased. The increased exposure required dosage adjustments of 14-29% in three out of four patients.(7)

Selected Immunosuppressants/Selected Azole Antifungal Agents

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: The metabolism of cyclosporine, sirolimus, and temsirolimus by CYP3A4 may be inhibited by clotrimazole, isavuconazonium, itraconazole, and ketoconazole.

CLINICAL EFFECTS: Concurrent administration of an azole antifungal may result in elevated levels of and toxicity from cyclosporine, sirolimus, or temsirolimus.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Cyclosporine, sirolimus, or temsirolimus levels and renal function should be monitored if an azole antifungal is initiated or discontinued from concurrent therapy. The dosage of cyclosporine, sirolimus, or temsirolimus may need to be adjusted. Guidelines from the American Society of Transplantation recommend avoiding concurrent use of cyclosporine with itraconazole or ketoconazole. If the combination must be used, lower the dose of the immunosuppressant by at least 50 % and monitor levels closely.(42) The American Society of Transplantation guidelines state that concurrent use of sirolimus is contraindicated with ketoconazole and is not recommended with itraconazole.(42) The manufacturer of sirolimus states that the concurrent use of itraconazole or ketoconazole is not recommended and should be avoided,(25) while the US manufacturer of itraconazole states that concurrent therapy with sirolimus or temsirolimus (IV) is not recommended during and two weeks after itraconazole treatment.(41) The US manufacturer of temsirolimus recommends that concurrent therapy with strong CYP3A4 inhibitors such as itraconazole or ketoconazole be avoided. If concurrent use is warranted, a dosage reduction to 12.5 mg/week of temsirolimus should be considered. If the azole is discontinued, a washout period of 1 week should be allowed before adjusting the dosage of temsirolimus to previous levels.(27) The US manufacturer of sirolimus protein-bound injection (Fyarro) states a dose reduction to 56 mg/m2 is recommended when used concurrently with moderate or weak CYP3A4 inhibitors. Concurrent use with strong CYP3A4 inhibitors should be avoided.(44)

DISCUSSION: Clotrimazole, fluconazole, itraconazole and ketoconazole have been reported to increase cyclosporine concentrations although the documentation is most supportive of the interaction with ketoconazole. Exercise caution when stopping the antifungal agent as cyclosporine concentration may decrease. Concurrent isavuconazonium increased the area-under-curve (AUC) of cyclosporine (300 mg) by approximately 1.3-fold. There have been several case reports of increased sirolimus levels with concurrent fluconazole and itraconazole therapy and decreased levels of sirolimus after discontinuation of itraconazole. Concurrent isavuconazonium increased the maximum concentration (Cmax) and AUC of sirolimus (2 mg) by approximately 1.6-fold and 1.8-fold, respectively. In a multiple-dose study, concomitant administration of ketoconazole with sirolimus oral solution increased the sirolimus Cmax, time to Cmax (Tmax), and AUC by 4.3-fold, 38%, and 10.9-fold, respectively. Single-dose sirolimus did not affect steady-state 12-hour plasma ketoconazole concentrations. In a study in 6 patients, ketoconazole was successfully used to augment sirolimus levels. Patients were able to receive one-eight to one-fourth (0.25 - 0.50 mg daily) of the usual sirolimus dose while taking 100 to 200 mg of ketoconazole daily. Concurrent administration of ketoconazole had no effects on temsirolimus AUC or Cmax; however, sirolimus AUC and Cmax increased 3.1-fold and 2.2-fold, respectively. Dosage adjustment of temsirolimus to 12.5 mg/week in the presence of strong CYP3A4 inhibitors is expected to adjust levels to the range observed without inhibitors; however, there are no data available with this dose adjustment.

Selected Immunosuppressants/Selected Strong Cyp3a4 Inducers

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Strong CYP3A4 inducers may induce the metabolism of cyclosporine, everolimus, sirolimus and temsirolimus.(1-5)

CLINICAL EFFECTS: Concurrent use of strong inducers of CYP3A4 may result in decreased levels and effectiveness of cyclosporine, everolimus, sirolimus and temsirolimus.(1)

PREDISPOSING FACTORS: Induction effects may be more likely with regular use of the inducer for longer than 1-2 weeks.

PATIENT MANAGEMENT: If possible, consider alternatives to strong CYP3A4 inducers in patients maintained on cyclosporine and sirolimus. If concurrent therapy is warranted, monitor cyclosporine and sirolimus serum levels and observe the patient for graft rejection. The dosage of cyclosporine and sirolimus may need to be adjusted following the initiation or discontinuation of these agents. The US manufacturer of everolimus states that concurrent use with strong CYP3A4 inducers should be avoided. If concurrent use is warranted, consider increasing the dose of everolimus. In patients with advanced hormone receptor-positive, HER2-negative breast cancer (HR+BC); advanced pancreatic neuroendocrine tumors (PNET); or advanced renal cell carcinoma; or renal angiomyolipoma with TSC, double the daily dose of everolimus using 5 mg increments or less. If the inducer is discontinued, return the dose to that used prior to inducer therapy once the inducer has been stopped for 5 days. In patients with subependymal giant cell astrocytoma with TSC, double the dose of everolimus using 5 mg increments or less. Subsequent dosing should be individualized based on therapeutic drug monitoring. If the inducer is discontinued, return the dose of everolimus to the dose used prior to the inducer once the inducer has been stopped for 5 days, and assess everolimus trough levels 2 weeks later.(1) The US manufacturer of temsirolimus states that concurrent use of strong inducers of CYP3A4, such as carbamazepine, phenobarbital, phenytoin, rifabutin, rifampicin, or rifampin should be avoided. If concurrent therapy is warranted, consider increasing the dosage of temsirolimus from 25 mg/week to 50 mg/week. If the inducer is discontinued, the dosage of temsirolimus should be returned to the previous dose.(2) If possible, consider alternatives to strong CYP3A4 inducers in patients maintained on cyclosporine and sirolimus. If concurrent therapy is warranted, monitor cyclosporine and sirolimus serum levels and observe the patient for graft rejection. The dosage of cyclosporine and sirolimus may need to be adjusted following the initiation or discontinuation of these agents.

DISCUSSION: Encorafenib and ivosidenib are strong CYP3A4 inducers. Other strong CYP3A4 inducers have been documented to decrease exposure to cyclosporine, everolimus, sirolimus, and temsirolimus. In a study in 10 lung transplant patients, significantly higher doses of cyclosporine were required during nafcillin therapy to maintain therapeutic trough levels. Patients also developed higher serum creatinine levels and more renal dysfunction than patients not receiving nafcillin. In a case report, a patient experienced 70% and 85% drops in cyclosporine levels during two separate courses of nafcillin therapy. Trough cyclosporine concentrations have been found to decrease within 48 hours after starting phenytoin even when the dose of cyclosporine is increased. Conversely, cyclosporine concentrations may increase when the hydantoin is discontinued. The effect of the hydantoin on cyclosporine may reverse over a period of one to three weeks after stopping the hydantoin. Concurrent administration of cyclosporine and rifampin has been associated with lowering of cyclosporine to undetectable serum levels. Decreases in cyclosporine levels have been observed within 2 days of concomitant therapy but will probably not be maximal for 1 week. The effects of the interaction may persist for up to 3 weeks after rifampin is stopped. In an open-label study in 11 renal transplant patients, subjects received St. John's wort (600 mg daily) for 14 days in addition to their normal cyclosporine regimen. After 14 days of St. John's wort, dose-corrected cyclosporine area-under-curve (AUC), maximum concentration (Cmax), and minimum concentration (Cmin) decreased by 46%, 42%, and 41%, respectively. Mean cyclosporine dose increased from 2.7 mg/kg/day at 4.2 mg/kg/day at the end of the study. Subjects required their first cyclosporine dosage adjustment at Day 3. There are several case reports of decreased cyclosporine with concurrent carbamazepine, phenobarbital, and St. John's wort. In healthy subjects, concurrent use of rifampin, a strong inducer of CYP3A4, decreased everolimus AUC and Cmax by 64% and 58%, respectively. Increasing the dosage of everolimus to 20 mg daily in patients taking a strong inducer of CYP3A4 is expected to increase the AUC of everolimus to levels seen without a concurrent inducer; however, there are no clinical data available with this dosage in patients receiving strong CYP3A4 inducers. In an open-label clinical trial, 10 male patients received ridaforolimus (40 mg daily, days 1 and 14) and rifampin (600 mg daily, days 1-21). Administration of rifampin resulted in a reduction in the mean whole-blood concentration of ridaforolimus (AUC-GMR 0.57, Cmax- GMR 0.66). The mean whole-blood concentration of ridaforolimus increased 1.5-fold following ketoconazole administration. In a study in 14 healthy subjects, pretreatment with rifampin (600 mg daily for 14 days) decreased the AUC and Cmax of a single dose of sirolimus (20 mg) by 82% and 71%, respectively. The oral clearance of sirolimus increased by 5.5-fold. There are case report of decreased sirolimus levels with concurrent phenytoin and rifampin. Concurrent rifampin had no significant effects on the AUC or Cmax of temsirolimus; however, sirolimus AUC and Cmax decreased by 56% and 65%, respectively. A dosage adjustment to 50 mg/week of temsirolimus in the presence of strong CYP3A4 inducers is predicted to adjust levels to those seen without inducers; however, there are no clinical data in patients using this dose. There is a case report of decreased temsirolimus effectiveness with concurrent rifampin.

Selected Immunosuppressants/Strong Cyp3a4 Inducers

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Strong inducers of CYP3A4 may increase the metabolism of cyclosporine, everolimus, sirolimus, tacrolimus, and temsirolimus.(1)

CLINICAL EFFECTS: Concurrent use of strong inducers of CYP3A4 may result in decreased levels and effectiveness of cyclosporine, everolimus, sirolimus, tacrolimus, and temsirolimus.(1)

PREDISPOSING FACTORS: Induction effects may be more likely with regular use of the inducer for longer than 1-2 weeks.

PATIENT MANAGEMENT: The American Society of Transplantation guidelines state that cyclosporine and tacrolimus should be avoided in combination with rifabutin and rifampin. Everolimus should be avoided in combination with rifampin and is contraindicated with rifabutin. Sirolimus is contraindicated with rifabutin and rifampin. If concurrent therapy of cyclosporine, everolimus, sirolimus, or tacrolimus with rifampin is needed, increase the dose of the immunosuppressant by 2-fold when the combination is initiated and monitor immunosuppressant concentrations frequently with rapid subsequent dose increases as needed. The reverse is recommended when rifampin is discontinued.(62) The US manufacturer of everolimus states that concurrent use with strong CYP3A4 inducers should be avoided. If concurrent use is warranted, consider increasing the dose of everolimus. In patients with advanced hormone receptor-positive, HER2-negative breast cancer (HR+BC); advanced pancreatic neuroendocrine tumors (PNET); or advanced renal cell carcinoma; or renal angiomyolipoma with TSC, double the daily dose of everolimus using 5 mg increments or less. If the inducer is discontinued, return the dose to that used prior to inducer therapy once the inducer has been stopped for 5 days. In patients with subependymal giant cell astrocytoma with TSC, double the dose of everolimus using 5 mg increments or less. Subsequent dosing should be individualized based on therapeutic drug monitoring. If the inducer is discontinued, return the dose of everolimus to the dose used prior to the inducer once the inducer has been stopped for 5 days, and assess everolimus trough levels 2 weeks later.(1) St. John's wort may decrease everolimus levels unpredictably and should be avoided entirely.(1) The US manufacturer of temsirolimus states that concurrent use of strong inducers of CYP3A4, such as carbamazepine, phenobarbital, phenytoin, rifabutin, rifampicin, or rifampin should be avoided. If concurrent therapy is warranted, consider increasing the dosage of temsirolimus from 25 mg/week to 50 mg/week. If the inducer is discontinued, the dosage of temsirolimus should be returned to the previous dose.(2) If possible, consider alternatives to strong CYP3A4 inducers in patients maintained on cyclosporine, sirolimus, and tacrolimus. If concurrent therapy is warranted, monitor cyclosporine, sirolimus, and tacrolimus serum levels and observe the patient for graft rejection. The dosage of cyclosporine, sirolimus, and tacrolimus may need to be adjusted following the initiation or discontinuation of these agents. Strong CYP3A4 inducers linked to this monograph include: allobarbital, amobarbital, apalutamide, aprobarbital, barbexaclone, barbital, brallobarbital, butabarbital, butalbital, butethal, carbamazepine, cyclobarbital, difebarbamate, ethotoin, febarbamate, fosphenytoin, hexobarbital, lumacaftor, mephenytoin, mephobarbital, metharbital, mitotane, natisedine, pentobarbital, phenobarbital, phenytoin, primidone, probarbital, proxibarbal, rifabutin, rifampin, rifapentine, secobarbital, St. John's wort, talbutal, vinbarbital, and vinylbital.

DISCUSSION: In a study in 10 lung transplant patients, significantly higher doses of cyclosporine were required during nafcillin therapy to maintain therapeutic trough levels. Patients also developed higher serum creatinine levels and more renal dysfunction than patients not receiving nafcillin. In a case report, a patient experienced 70% and 85% drops in cyclosporine levels during two separate courses of nafcillin therapy. Trough cyclosporine concentrations have been found to decrease within 48 hours after starting phenytoin even when the dose of cyclosporine is increased. Conversely, cyclosporine concentrations may increase when the hydantoin is discontinued. The effect of the hydantoin on cyclosporine may reverse over a period of one to three weeks after stopping the hydantoin. Concurrent administration of cyclosporine and rifampin has been associated with lowering of cyclosporine to undetectable serum levels. Decreases in cyclosporine levels have been observed within 2 days of concomitant therapy but will probably not be maximal for 1 week. The effects of the interaction may persist for up to 3 weeks after rifampin is stopped. In an open-label study in 11 renal transplant patients, subjects received St. John's wort (600 mg daily) for 14 days in addition to their normal cyclosporine regimen. After 14 days of St. John's wort, dose-corrected cyclosporine area-under-curve (AUC), maximum concentration (Cmax), and minimum concentration (Cmin) decreased by 46%, 42%, and 41%, respectively. Mean cyclosporine dose increased from 2.7 mg/kg/day at 4.2 mg/kg/day at the end of the study. Subjects required their first cyclosporine dosage adjustment at Day 3. There are several case reports of decreased cyclosporine with concurrent carbamazepine, phenobarbital, and St. John's wort. In healthy subjects, concurrent use of rifampin, a strong inducer of CYP3A4, decreased everolimus AUC and Cmax by 64% and 58%, respectively. Increasing the dosage of everolimus to 20 mg daily in patients taking a strong inducer of CYP3A4 is expected to increase the AUC of everolimus to levels seen without a concurrent inducer; however, there are no clinical data available with this dosage in patients receiving strong CYP3A4 inducers. In an open-label clinical trial, 10 male patients received ridaforolimus (40 mg daily, days 1 and 14) and rifampin (600 mg daily, days 1-21). Administration of rifampin resulted in a reduction in the mean whole-blood concentration of ridaforolimus (AUC-GMR 0.57, Cmax- GMR 0.66). The mean whole-blood concentration of ridaforolimus increased 1.5-fold following ketoconazole administration. In a study in 14 healthy subjects, pretreatment with rifampin (600 mg daily for 14 days) decreased the AUC and Cmax of a single dose of sirolimus (20 mg) by 82% and 71%, respectively. The oral clearance of sirolimus increased by 5.5-fold. There are case report of decreased sirolimus levels with concurrent phenytoin and rifampin. A study in six healthy subjects examined the effects of rifampin on single doses of oral (0.1 mg/kg) and intravenous (0.025 mg/kg/4 hours) tacrolimus. Rifampin increased tacrolimus clearance by 47% and decreased tacrolimus bioavailability by 51%. In a study in 10 healthy subjects, pretreatment with St. John's wort (300 mg 3 times daily for 18 days) decreased the AUC of a single dose of tacrolimus (0.1 mg/kg) by 35.3%. Tacrolimus apparent oral clearance and volume of distribution increased by 68% and 53%, respectively. In a study in 10 renal transplant patients, concurrent St. John's wort (600 mg daily) for 2 weeks increased tacrolimus dose requirements from a baseline of 4.5 mg/day to 8.0 mg/day. Dose-correct tacrolimus AUC decreased by 57.8%. There have been several case reports of decreased tacrolimus levels with concurrent carbamazepine, phenobarbital, phenytoin, rifampin, and St. John's wort. Phenobarbital and phenytoin have been used successfully to treat tacrolimus overdose. Concurrent rifampin had no significant effects on the AUC or Cmax of temsirolimus; however, sirolimus AUC and Cmax decreased by 56% and 65%, respectively. A dosage adjustment to 50 mg/week of temsirolimus in the presence of strong CYP3A4 inducers is predicted to adjust levels to those seen without inducers; however, there are no clinical data in patients using this dose. There is a case report of decreased temsirolimus effectiveness with concurrent rifampin.

Selected Immunosuppressants/Voriconazole

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: The metabolism of cyclosporine and temsirolimus by CYP3A4 may be inhibited by voriconazole.(1-2)

CLINICAL EFFECTS: Concurrent administration of voriconazole may result in elevated levels of and toxicity from cyclosporine or temsirolimus.(1-2)

PREDISPOSING FACTORS: Concurrent use of voriconazole in patients who are poor or intermediate CYP2C19 metabolizers may necessitate larger immunosuppressant dose adjustments than in patients who are extensive CYP2C19 metabolizers.(3)

PATIENT MANAGEMENT: Cyclosporine or temsirolimus levels and renal function should be monitored if voriconazole is initiated or discontinued from concurrent therapy.(1-2) The manufacturer of voriconazole recommends that the dose of cyclosporine be reduced by 50% when used with voriconazole.(1) Cyclosporine levels should be closely monitored during concurrent azole therapy. The dosage of cyclosporine may need adjusting when azole therapy has been completed.(1) The US manufacturer of temsirolimus recommends that concurrent therapy with strong CYP3A4 inhibitors be avoided. If concurrent use is warranted, a dosage reduction to 12.5 mg/week of temsirolimus should be considered. If the azole is discontinued, a washout period of 1 week should be allowed before adjusting the dosage of temsirolimus to previous levels.(2)

DISCUSSION: In renal transplant recipients, voriconazole (200 mg orally every 12 hours for 8 days) increased the maximum concentration (Cmax), area-under-curve (AUC), and trough concentration (Cmin) of cyclosporine by 1.1-fold, 1.7-fold, and 2.48-fold, respectively.(4)

Selected Immunosuppressants; Temsirolimus/Saquinavir

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Saquinavir may inhibit the metabolism of cyclosporine, sirolimus, and temsirolimus by CYP3A4.(1-2)

CLINICAL EFFECTS: Concurrent use of saquinavir may result in increased levels of cyclosporine, sirolimus, or temsirolimus.(1-2)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: For patients concurrently taking cyclosporine, sirolimus, or temsirolimus and saquinavir, therapeutic concentration monitoring of the immunosuppressant is recommended. Depending upon the agents involved, dose decreases of the immunosuppressant agent may be required.(1-2) The US manufacturer of temsirolimus recommends that concurrent therapy with strong CYP3A4 inhibitors such as saquinavir be avoided. If concurrent use is warranted, a dosage reduction to 12.5 mg/week of temsirolimus should be considered. If saquinavir is discontinued, an elimination period of 1 week should be allowed before adjusting the dosage of temsirolimus to previous levels.(2) The selected immunosuppressants linked to this monograph include: cyclosporine, sirolimus, and temsirolimus.

DISCUSSION: Concurrent administration of ketoconazole, another inhibitor of CYP3A4, had no effects on temsirolimus AUC or Cmax; however, sirolimus AUC and Cmax increased 3.1-fold and 2.2-fold, respectively. Dosage adjustment of temsirolimus to 12.5 mg/week in the presence of strong CYP3A4 inhibitors is expected to adjust levels to the range observed without inhibitors; however, there are no data available with this dose adjustment.(2) In a study in 3 HIV+ transplant patients who were receiving lopinavir/ritonavir, another strong inhibitor of CYP3A4, cyclosporine doses were reduced to 5-20% of standard doses to prevent toxicity.(3) One case report describes a 52 year-old male with HIV and hepatitis C who experienced severe tacrolimus toxicity after the addition of an HIV regimen including nelfinavir (750 mg three times daily) following his liver transplantation. The HIV regimen was temporarily stopped until the tacrolimus levels normalized at which time the medications were restarted having replaced nelfinavir with saquinavir (400 mg twice/day) and ritonavir (400 mg twice/day). The patient again experienced neurological symptoms associated with tacrolimus toxicity and was found to have a tacrolimus level over 120 ng/ml. The medications were held allowing for a long recovery. The HIV regimen was rechallenged a third time using the original combination which included nelfinavir. The dose of tacrolimus was dramatically decreased and the schedule changed until the tacrolimus levels finally stabilized.(4)

Selected Nephrotoxic Agents/Colistimethate

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Colistimethate can cause nephrotoxicity.(1,2) Concurrent administration of other nephrotoxic agents may result in an increased risk of nephrotoxicity.(1) It is suspected that cephalothin interferes with the excretion of colistimethate resulting in enhanced nephrotoxicity.(2,3)

CLINICAL EFFECTS: Concurrent use of colistimethate with other nephrotoxic agents may result in additive nephrotoxic effects.

PREDISPOSING FACTORS: Factors predisposing to nephrotoxicity include higher cumulative doses of colistimethate, longer treatment duration, hypovolemia, and critical illness.

PATIENT MANAGEMENT: Concurrent use of potentially nephrotoxic agents with colistimethate should be avoided.(1,2) If concurrent use is necessary, it should be undertaken with great caution.(1)

DISCUSSION: In a case control study of 42 patients on intravenous colistimethate sodium, NSAIDs were identified as an independent risk factor for nephrotoxicity (OR 40.105, p=0.044).(4) In 4 case reports, patients developed elevated serum creatinine and blood urea nitrogen following concurrent colistimethate and cephalothin (3 patients) or when colistimethate followed cephalothin therapy (1 patient).(3) A literature review found that individual nephrotoxic agents, including aminoglycosides, vancomycin, amphotericin, IV contrast, diuretics, ACE inhibitors, ARBs, NSAIDs, and calcineurin inhibitors, were not consistently associated with additive nephrotoxicity when used with colistimethate. However, when multiple agents (at least 2 additional potential nephrotoxins) were used concurrently, there was a significant correlation to colistimethate nephrotoxicity.(5)

Selected Nephrotoxic Agents/Foscarnet

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Foscarnet is nephrotoxic. Concurrent administration of other nephrotoxic agents may result in additive or synergistic effects on renal function.(1) Concurrent intravenous pentamidine may also result in hypocalcemia.(1)

CLINICAL EFFECTS: Concurrent use of foscarnet with nephrotoxic agents such as acyclovir, adefovir, intravenous aminoglycosides, amphotericin B, cyclosporine, methotrexate, non-steroidal anti-inflammatory agents, intravenous pentamidine, tacrolimus, tenofovir, vancomycin and voclosporin may result in renal toxicity.(1) Other nephrotoxic agents include capreomycin, cisplatin, gallium nitrate, high-dose methotrexate, and streptozocin.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of foscarnet state that concurrent administration of potentially nephrotoxic agents such as acyclovir, intravenous aminoglycosides, amphotericin B, cyclosporine, methotrexate, tacrolimus, and intravenous pentamidine should be avoided.(1) Other nephrotoxic agents include adefovir, capreomycin, cisplatin, gallium nitrate, high-dose methotrexate, non-steroidal anti-inflammatory agents, streptozocin, tenofovir, vancomycin and voclosporin. If concurrent therapy is warranted, monitor renal function closely. In patients receiving concurrent foscarnet and pentamidine, also monitor serum calcium levels and instruct patients to report severe muscle spasms, mental/mood changes, and/or seizures.(1)

DISCUSSION: The safety of foscarnet has not been studied in patients receiving other known potentially nephrotoxic agents. Renal impairment is the major toxicity of foscarnet.(1)

Selected Nephrotoxic Agents/Inotersen

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Inotersen can cause glomerulonephritis and renal toxicity. Concurrent administration of other nephrotoxic agents may result in additive or synergistic effects on renal function.(1)

CLINICAL EFFECTS: Concurrent use of inotersen with nephrotoxic agents such as acyclovir, adefovir, intravenous aminoglycosides, amphotericin B, cyclosporine, methotrexate, non-steroidal anti-inflammatory agents, intravenous pentamidine, tacrolimus, tenofovir, vancomycin and voclosporin may result in renal toxicity.(1) Other nephrotoxic agents include capreomycin, cisplatin, gallium nitrate, high-dose methotrexate, and streptozocin.

PREDISPOSING FACTORS: Patients with pre-existing renal impairment.

PATIENT MANAGEMENT: The US manufacturer of inotersen state that caution should be used when administered concurrently with potentially nephrotoxic agents or agents that impair renal function.(1) If concurrent therapy is warranted, monitor renal function closely.(1)

DISCUSSION: The safety of inotersen has not been studied in patients receiving other known potentially nephrotoxic agents. Inotersen is only available through a Tegsedi REMS program because of the risk of glomerulonephritis and severe thrombocytopenia.(1)

Selected Oatp1b1-3 Inhibitors/Voxilaprevir

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: OATP1B1 and OATP1B3 inhibitors may increase exposure to voxilaprevir.(1)

CLINICAL EFFECTS: Concurrent use of OATP1B1 and OATP1B3 inhibitors may result in increased levels of and toxicity from voxilaprevir.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Concurrent administration of voxilaprevir with OATP1B1 and OATP1B3 inhibitors is not recommended.(1,4) If concurrent therapy is warranted, monitor patients for adverse effects. The American Society of Transplantation guidelines state that the combination of voxilaprevir and cyclosporine is contraindicated.(3)

DISCUSSION: In a study in 25 subjects, cyclosporine (600 mg single dose) increased the maximum concentration (Cmax) and area-under-curve (AUC) of voxilaprevir (100 mg single dose) by 19.02-fold and 9.39-fold, respectively. There were no significant effects on cyclosporine levels.(1) OATP inhibitors include: atazanavir, belumosudil, cyclosporine, encorafenib, fostemsavir, leniolisib, letermovir, lopinavir, paritaprevir, resmetirom, roxadustat, vadadustat, and voclosporin.(1,2,4)

Selected P-Glycoprotein (P-GP) Inhibitors/Dabigatran

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Dabigatran etexilate is a substrate for the P-glycoprotein (P-gp) system. Inhibition of intestinal P-gp leads to increased absorption of dabigatran.(1-3)

CLINICAL EFFECTS: The concurrent use dabigatran with P-gp inhibitors may lead to elevated plasma levels of dabigatran, increasing the risk for bleeding.

PREDISPOSING FACTORS: Factors associated with an increased risk for bleeding include renal impairment, concomitant use of P-gp inhibitors, patient age >74 years, coexisting conditions (e.g. recent trauma) or use of drugs (e.g. NSAIDs) associated with bleeding risk, and patient weight < 50 kg.(1-4)

PATIENT MANAGEMENT: Assess renal function and evaluate patient for other pre-existing risk factors for bleeding prior to initiating concurrent therapy. The US manufacturer of dabigatran states that the concurrent use of dabigatran and P-gp inhibitors should be avoided in atrial fibrillation patients with severe renal impairment (CrCl less than 30 ml/min) and in patients with moderate renal impairment (CrCl less than 50 ml/min) being treated for or undergoing prophylaxis for deep vein thrombosis (DVT) or pulmonary embolism (PE). The interaction with P-gp inhibitors can be minimized by taking dabigatran several hours apart from the P-gp inhibitor dose.(1) The concomitant use of dabigatran with P-gp inhibitors has not been studied in pediatric patients but may increase exposure to dabigatran.(1) While the US manufacturer of dabigatran states that no dosage adjustment is necessary in other patients,(1) the Canadian manufacturer of dabigatran states that concomitant use of strong P-gp inhibitors (e.g., glecaprevir-pibrentasvir) is contraindicated. When dabigatran is used for the prevention of venous thromboembolism (VTE) after total hip or knee replacement concurrently with amiodarone, quinidine, or verapamil, the dose of dabigatran should be reduced from 110 mg twice daily to 150 mg once daily. For patients with CrCl less than 50 ml/min on verapamil, a further dabigatran dose reduction to 75 mg once daily should be considered. Verapamil should be given at least 2 hours after dabigatran to minimize the interaction.(2) The UK manufacturer of dabigatran also states the use of dabigatran with strong P-gp inhibitors (e.g., cyclosporine, glecaprevir-pibrentasvir or itraconazole) is contraindicated. Concurrent use of ritonavir is not recommended. When dabigatran is used in atrial fibrillation patients and for treatment of DVT and PE concurrently with verapamil, the UK manufacturer recommends reducing the dose of dabigatran from 150 mg twice daily to 110 mg twice daily, taken simultaneously with verapamil. When used for VTE prophylaxis after orthopedic surgery concurrently with amiodarone, quinidine, or verapamil, the dabigatran loading dose should be reduced from 110 mg to 75 mg, and the maintenance dose should be reduced from 220 mg daily to 150 mg daily, taken simultaneously with the P-gp inhibitor. For patients with CLcr 30-50 mL/min on concurrent verapamil, consider further lowering the dabigatran dose to 75 mg daily.(3) If concurrent therapy is warranted, monitor patients for signs of blood loss, including decreased hemoglobin and/or hematocrit, fecal occult blood, and/or decreased blood pressure and promptly evaluate patients with any symptoms. Consider regular monitoring of hemoglobin, platelet levels, and/or activated partial thromboplastin time (aPTT) or ecarin clotting time (ECT). When applicable, perform agent-specific laboratory test (e.g. INR, aPTT) to monitor efficacy and safety of anticoagulation. Discontinue anticoagulation in patients with active pathologic bleeding. Instruct patients to report any signs and symptoms of bleeding, such as unusual bleeding from the gums or nose; unusual bruising; red or black, tarry stools; red, pink or dark brown urine; acute abdominal or joint pain and/or swelling. The manufacturer of daraxonrasib states P-gp substrates should be administered at least 4 hours apart from daraxonrasib.(10)

DISCUSSION: When dabigatran was co-administered with amiodarone, the extent and rate of absorption of amiodarone and its active metabolite DEA were essentially unchanged. The dabigatran area-under-curve (AUC) and maximum concentration (Cmax) were increased by about 60% and 50%, respectively;(1,2) however, dabigatran clearance was increased by 65%.(1) Pretreatment with quinidine (200 mg every 2 hours to a total dose of 1000 mg) increased the AUC and Cmax of dabigatran by 53% and 56%, respectively.(1,2) Chronic administration of immediate release verapamil one hour prior to dabigatran dose increased dabigatran AUC by 154%.(4) Administration of dabigatran two hours before verapamil results in a negligible increase in dabigatran AUC.(1) Administration of sofosbuvir-velpatasvir-voxilaprevir (400/100/200 mg daily) increased the Cmax and AUC of a single dose of dabigatran (75 mg) by 2.87-fold and 2.61-fold, respectively.(5) Simultaneous administration of glecaprevir-pibrentasvir (300/120 mg daily) with a single dose of dabigatran (150 mg) increased the Cmax and AUC by 2.05-fold and 2.38-fold, respectively.(6) A retrospective comparative effectiveness cohort study including data from 9,886 individuals evaluated adverse bleeding rates with standard doses of oral anticoagulants with concurrent verapamil or diltiazem in patients with nonvalvular atrial fibrillation and normal kidney function. The study compared rates of bleeding following co-administration of either dabigatran, rivaroxaban, or apixaban with verapamil or diltiazem, compared to co-administration with amlodipine or metoprolol. Results of the study found that concomitant dabigatran use with verapamil or diltiazem was associated with increased overall bleeding (hazard ratio (HR) 1.52; 95% confidence interval (CI), 1.05-2.20, p<0.05) and increased overall GI bleeding (HR 2.16; 95% CI, 1.30-3.60, p<0.05) when compared to amlodipine. When compared to metoprolol, concomitant dabigatran use with verapamil or diltiazem was also associated with increased overall bleeding (HR, 1.43; 95% CI, 1.02-2.00, p<0.05) and increased overall GI bleeding (HR, 2.32; 95% CI, 1.42-3.79, p<0.05). No association was found between increased bleeding of any kind and concurrent use of rivaroxaban or apixaban with verapamil or diltiazem.(7) A summary of pharmacokinetic interactions with dabigatran and amiodarone or verapamil concluded that concurrent use is considered safe if CrCl is greater than 50 ml/min but should be avoided if CrCl is less than 50 ml/min in VTE and less than 30 ml/min for NVAF. Concurrent use with diltiazem was considered safe.(9) P-gp inhibitors include amiodarone, asunaprevir, aumolertinib, belumosudil, capmatinib, carvedilol, cimetidine, conivaptan, cyclosporine, daclatasvir, danicopan, daraxonrasib, daridorexant, diosmin, erythromycin, flibanserin, fostamatinib, ginseng, glecaprevir, imlunestrant, indinavir, itraconazole, ivacaftor, josamycin, lapatinib, ledipasvir, lonafarnib, mavorixafor, neratinib, osimertinib, pibrentasvir, posaconazole, propafenone, quinidine, ranolazine, ritonavir, selpercatinib, sotorasib, telaprevir, telithromycin, tepotinib, tezacaftor, tucatinib, valbenazine, velpatasvir, vemurafenib, vepdegestrant, verapamil, vimseltinib, voclosporin, and voxilaprevir.(1-9)

Selected P-Glycoprotein (P-GP) Substrates/Venetoclax

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Venetoclax is an inhibitor of the P-glycoprotein (P-gp) system and may increase the absorption of P-gp substrates.(1)

CLINICAL EFFECTS: Concurrent use of venetoclax with P-gp substrates may result in elevated levels and toxicities of the substrate.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of venetoclax states that the concurrent use of P-gp substrates should be avoided. If concurrent therapy cannot be avoided, the P-gp substrate should be taken at least 6 hours before venetoclax.(1) If concurrent therapy with afatinib is unavoidable and not tolerated, the US manufacturer of afatinib states that the afatinib dose should be reduced by 10 mg. Resume the previous dose of afatinib if venetoclax is discontinued.(2) The manufacturer of ubrogepant recommends a dosage adjustment of ubrogepant when coadministered with P-gp inhibitors. The initial dose of ubrogepant should not exceed 50 mg. If a second dose of ubrogepant is needed, the dose should not exceed 50 mg.(8)

DISCUSSION: In vitro data suggests venetoclax is a P-gp inhibitor at therapeutic doses in the gut.(1) Administration of a single venetoclax 100 mg dose with digoxin increased the maximum concentration (Cmax) and area-under-the-curve of digoxin by 35% and 9%, respectively.(1) Selected P-gp substrates linked to this monograph include: afatinib, aliskiren, betrixaban, bilastine, cyclosporine, dabigatran, digoxin, edoxaban, everolimus, loperamide, sirolimus, talazoparib, topotecan, and ubrogepant.(1-9)

Selected P-Gp Inhibitors/Edoxaban (> 30 MG)

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Edoxaban is a substrate for P-glycoprotein (P-gp). Inhibitors of P-gp may increase intestinal absorption and decrease renal tubular elimination of edoxaban.(1,2)

CLINICAL EFFECTS: Concurrent use with selected P-gp inhibitors may result in higher systemic concentrations of edoxaban which may increase the risk for bleeding.(1-5) P-gp inhibitors linked to this interaction are: cyclosporine, dronedarone, erythromycin, and ketoconazole.

PREDISPOSING FACTORS: Bleeding risk may be increased in patients with creatinine clearance 15mL - 50 mL per minute(1) or weight < or = 60 kg.(2) Use of multiple agents which increase edoxaban exposure or affect hemostasis would be expected to increase the risk for bleeding. The risk for bleeding episodes may be greater in patients with disease-associated factors (thrombocytopenia). Drug associated risk factors include concurrent use of multiple drugs which inhibit anticoagulant/antiplatelet metabolism and/or have an inherent risk for bleeding (e.g. NSAIDs).

PATIENT MANAGEMENT: Management recommendations vary depending upon the approving regulatory agency (FDA or European Medicines Agency, EMA). US FDA recommendations are based upon the edoxaban indication: - For treatment of deep vein thrombosis (DVT) or pulmonary embolism (PE), the edoxaban dose should be reduced to 30 mg daily when used concomitantly with erythromycin or oral ketoconazole.(3) - For prevention of stroke or embolic events due to nonvalvular atrial fibrillation, no edoxaban dose adjustments are recommended during concomitant therapy with P-glycoprotein inhibitors.(1,3) - Concurrent use of cyclosporine was not allowed in edoxaban clinical trials (atrial fibrillation or DVT/PE). US prescribing information does not provide specific management information for concurrent use of cyclosporine with edoxaban.(3) EMA dosage adjustments are the same, regardless of indication: - Reduce edoxaban dose to 30 mg daily in patients receiving concomitant treatment with cyclosporine, dronedarone, erythromycin or oral ketoconazole.(4) Monitor patients receiving concurrent therapy for signs of blood loss, including decreased hemoglobin and/or hematocrit, fecal occult blood, and/or decreased blood pressure and promptly evaluate patients with any symptoms. When applicable, perform agent-specific laboratory test (e.g. anti Factor Xa inhibition) to monitor efficacy and safety of anticoagulation. Discontinue anticoagulation in patients with active pathologic bleeding. Instruct patients to report any signs and symptoms of bleeding, such as unusual bleeding from the gums or nose; unusual bruising; red or black, tarry stools; red, pink or dark brown urine; acute abdominal or joint pain and/or swelling. Discontinue edoxaban in patients with active bleeding.

DISCUSSION: Edoxaban in vivo interaction studies have been performed for P-gp inhibitors linked to this monograph: In an interaction study, the effect of single oral dose of cyclosporine 500 mg on a single oral dose of edoxaban 60 mg was evaluated in healthy subjects. Total and peak systemic exposure to edoxaban increased 1.73-fold and 1.74-fold, respectively. Total and peak systemic exposure to the active M4 metabolite increased 6.87-fold and 8.71-fold respectively, likely due to cyclosporine inhibition of OATP1B1.(1) In the absence of OATP1B1 inhibition, M4 concentrations are generally < or = 10% of edoxaban exposure,(1) but the approximately 7-fold increase in active metabolite exposure may result in clinically meaningful concentrations of M4. In an interaction study, the effect of repeat administration of dronedarone (400 mg bid) on a single oral dose of edoxaban 60 mg was evaluated in healthy subjects. Total and peak systemic exposure to edoxaban increased 1.84-fold and 1.45-fold, respectively. Plasma edoxaban concentrations 24 hours post dose (Ctrough) following coadministration edoxaban and dronedarone were 2.6-fold higher compared with administration of edoxaban alone.(1) In an interaction study, the effect of repeat administration of erythromycin (oral dose of 500 mg four times daily for 8 days) on a single oral dose of edoxaban 60 mg on on study day 7 was evaluated in healthy subjects. Total and peak systemic exposure to edoxaban increased 1.85-fold and 1.68-fold, respectively. Total and peak systemic exposure to the M4 metabolite increased 1.78-fold and 1.75-fold, respectively.(1) In an interaction study, the effect of repeat administration of ketoconazole (oral dose of 400 mg QD for 7 days) on a single oral dose of edoxaban (60 mg) was evaluated in healthy subjects. Total and peak systemic exposure to edoxaban increased 1.87-fold and 1.89-fold, respectively. Total and peak systemic exposure to the M4 metabolite increased 1.46-fold and 1.56-fold, respectively.(1) A summary of pharmacokinetic interactions with edoxaban and dronedarone concluded that if concurrent use is warranted, the edoxaban dose should be reduced by 50%.(6)

Selected Sensitive Cyp3a4 Substrates/Tucatinib

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Tucatinib is a strong inhibitor of CYP3A4 and may decrease the metabolism of drugs metabolized by the CYP3A4 enzyme. Tucatinib is also an inhibitor of P-glycoprotein (P-gp) and may increase the absorption of sirolimus.

CLINICAL EFFECTS: Concurrent use of tucatinib may lead to increased serum levels and adverse effects of drugs sensitive to inhibition of the CYP3A4 pathway or P-gp.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of tucatinib states that coadministration of CYP3A4 substrates should be avoided. If concomitant use is unavoidable, consider dose reduction of the CYP3A4 substrate.(1) The manufacturer of tucatinib states that the dose of P-gp substrates may need to be reduced with coadministration with tucatinib.(1)

DISCUSSION: In a study, tucatinib increased the area-under-the-curve (AUC) and maximum concentration (Cmax) of a single dose of midazolam (2 mg) by 5.7-fold and 3-fold, respectively.(1) In a study, tucatinib increased the AUC and Cmax of digoxin (0.5 mg single dose) by 1.5-fold and 2.4-fold, respectively.(1) CYP3A4 substrates with a narrow therapeutic index linked to this monograph include: cyclosporine, midazolam, nisoldipine, and sirolimus.(1-3)

Selected Sensitive Cyp3a4 Substrates/Voxelotor

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Voxelotor is an inhibitor of CYP3A4 and may decrease the metabolism of drugs metabolized by the CYP3A4 enzyme.

CLINICAL EFFECTS: Concurrent use of voxelotor may lead to increased serum levels and adverse effects of drugs sensitive to inhibition of the CYP3A4 pathway.(1)

PREDISPOSING FACTORS: A greater risk for serious adverse events would be expected from drugs having a narrow therapeutic window.

PATIENT MANAGEMENT: The manufacturer of voxelotor states that co-administration of sensitive CYP3A4 substrates with a narrow therapeutic index should be avoided. If concomitant use is unavoidable, consider dose reduction of the sensitive substrate.(1)

DISCUSSION: In a study, voxelotor increased the AUC of a single dose of midazolam by 1.6-fold. After multiple doses of midazolam, a 2.5-fold increase in AUC is predicted.(1) Sensitive CYP3A4 substrates with a narrow therapeutic index linked to this monograph include: avanafil, conivaptan, cyclosporine, dihydroergotamine, eplerenone, ergotamine, everolimus, felodipine, fentanyl, lomitapide, lovastatin, methylergonovine, midazolam, nisoldipine, sildenafil, simvastatin, ticagrelor, tolvaptan, triazolam, and vardenafil.(2,3)

Sensitive Cyp3a4; Cyp2c9; Cyp2c19 Substrates/Enzalutamide

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Enzalutamide may induce the metabolism of agents metabolized by CYP3A4, CYP2C9, and CYP2C19.(1)

CLINICAL EFFECTS: Concurrent use of enzalutamide with agents metabolized by CYP3A4, CYP2C9, and CYP2C19 may result in decreased levels and effectiveness of these agents.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Avoid concurrent use of agents metabolized by CYP3A4, CYP2C9, or CYP2C19 that have a narrow therapeutic index with enzalutamide. If concurrent use is required, consider increased monitoring of the affected agent.(1) Dosage adjustments may be required.

DISCUSSION: In a clinical trial in healthy subjects, enzalutamide was shown to reduce the area-under-curve (AUC) of midazolam (a sensitive CYP3A4 substrate), warfarin (a sensitive CYP2C9 substrate), and omeprazole (a sensitive CYP2C19 substrate.(1) A case report in a 77-year-old Caucasian male was initiated on 160 mg of enzalutamide after being stable on warfarin with an INR of 3.5. The INR dropped to 1.4 after approximately 20 days on enzalutamide therapy. Due to the drop in INR, the warfarin dose was increased by 50% which lead to a therapeutic INR. When enzalutamide was discontinued, the warfarin dose was decreased by 33% to remain at a therapeutic level. Upon reinitiation, the warfarin dose was increased once by 50% to achieve a therapeutic INR.(2) Sensitive CYP3A4 substrates with narrow therapeutic indexes include: astemizole, cisapride, clarithromycin, cyclosporine, dihydroergotamine, ergonovine, ergotamine, pimozide, sirolimus, tacrolimus, temsirolimus, and terfenadine.(1,3,4) Sensitive CYP2C9 substrates with narrow therapeutic indexes include: warfarin.(1,3) Sensitive CYP2C19 substrates with narrow therapeutic indexes include: S-mephenytoin.(1,3)

Slt Immunosuppressants;Temsirolimus/Protease Inh;Cobicistat

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: HIV and HCV protease inhibitors as well as cobicistat may inhibit the metabolism of cyclosporine, sirolimus, and temsirolimus by CYP3A4.(1-15)

CLINICAL EFFECTS: Concurrent use of HIV or HCV protease inhibitors as well as cobicistat may result in increased levels of cyclosporine, sirolimus, or temsirolimus.(1-15)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: For patients concurrently taking cyclosporine, sirolimus, or temsirolimus and either a HIV or HCV protease inhibitor or cobicistat, therapeutic concentration monitoring of the immunosuppressant is recommended. Depending upon the agents involved, dose decreases of the immunosuppressant agent may be required.(1-15) Guidelines from the American Society of Transplantation recommend avoiding the use of ritonavir- or cobicistat-based HIV or HCV antiviral regimens with cyclosporine or sirolimus due to an increased risk of graft loss and death, as well as the availability of HIV integrase inhibitors that avoid interactions with immunosuppressants. If the combination must be used, lower the dose of cyclosporine to 25-50 mg daily or sirolimus to 1 mg once or twice weekly. Monitor drug concentrations closely.(1) The US manufacturer of sirolimus protein-bound injection (Fyarro) states a dose reduction to 56 mg/m2 is recommended when used concurrently with moderate or weak CYP3A4 inhibitors. Concurrent use with strong CYP3A4 inhibitors should be avoided.(16) The US manufacturer of temsirolimus recommends that concurrent therapy with strong CYP3A4 inhibitors such as protease inhibitors be avoided. If concurrent use is warranted, a dosage reduction to 12.5 mg/week of temsirolimus should be considered. If the protease inhibitor is discontinued, a washout period of 1 week should be allowed before adjusting the dosage of temsirolimus to previous levels.(2) The selected immunosuppressants linked to this monograph include: cyclosporine, sirolimus, and temsirolimus. The protease inhibitors linked to this monograph include: amprenavir, atazanavir, boceprevir, cobicistat, darunavir, fosamprenavir, indinavir, lopinavir, nelfinavir, ritonavir, telaprevir, and tipranavir.

DISCUSSION: A retrospective study of 42 HIV+ kidney transplant recipients examined rejection rates in patients on ritonavir-boosted protease inhibitor (PI) antiretroviral regimens compared to patients on other antiretroviral regimens. Immunosuppression therapy consisted of cyclosporine in 7 patients (17%) and tacrolimus in 32 patients (76%). The remaining 3 patients were transitioning between drugs. Over 3 years, 65% of patients on PI-based antiretroviral therapy experienced rejection, compared with 36% of patients on other antiretroviral therapies (p<0.001). There was no difference in patient or graft survival at 3 years.(17) Cyclosporine: Boceprevir (800 mg TID for 7 days) increased the Cmax and AUC of cyclosporine (100 mg single dose) by 2-fold and 2.68-fold, respectively. Boceprevir AUC increased 16%.(4) In a case report, cyclosporine dosage requirements decreased 12-fold following the addition of amprenavir/ritonavir. In another patient, cyclosporine dosage requirements decreased 3.5-fold following the addition of fosamprenavir.(18) In a study in 3 HIV+ transplant patients who were receiving lopinavir/ ritonavir, cyclosporine doses were reduced to 5-20% of standard doses to prevent toxicity.(19) In a clinical study, 7 HIV+ patients concurrently taking cyclosporine and nelfinavir experienced a 19% increase in time to Cmax (Tmax) and a 2-fold increase in AUC of cyclosporine when nelfinavir was added.(20) In a case report, cyclosporine levels tripled and signs of toxicity developed 3 days after the addition of saquinavir (1200 mg 3 times daily) to cyclosporine (150 mg twice daily). Cyclosporine and saquinavir dosages were decreased to 75 mg twice daily and 600 mg 3 times daily, respectively. Cyclosporine Cmin levels were 90% of those seen with 150 mg twice daily. Saquinavir AUC was 4.3-fold higher than in patients taking saquinavir 600 mg twice daily without cyclosporine and 11.1-fold higher than literature values.(21) In a study in 9 subjects, the concurrent administration of telaprevir (750 mg TID) decreased the Cmax and AUC of a single dose of cyclosporine (10 mg) by 87% and 54%, respectively, when compared to levels achieved with a single 100 mg dose of cyclosporine. Extrapolated to level expected with the 100 mg dose, cyclosporine Cmax and AUC would have increased by 32% and 4.64-fold, respectively.(5) Sirolimus: Boceprevir (800 mg TID for 9 days) increased the Cmax and AUC of sirolimus (2 mg single dose) by 4.84-fold and 8.121-fold, respectively. Boceprevir Cmin increased 21%.(4) In a case report, the pharmacokinetics of a liver transplant patient concurrently taking nelfinavir (250 mg) and sirolimus (2 mg) were compared to the pharmacokinetics in 3 other liver transplant patients that were also taking sirolimus, but not nelfinavir. The maximum concentration (Cmax) was 3.2 times higher, the area-under-curve (AUC) was 1.6 times higher, the half life was prolonged by 60%, and the 0-hr and 24-hour trough levels (Cmin) of sirolimus were 9-fold and 5-fold higher, respectively, in patients concurrently taking nelfinavir and sirolimus.(22) Temsirolimus: Concurrent administration of ketoconazole, another inhibitor of CYP3A4, had no effects on temsirolimus AUC or Cmax; however, sirolimus AUC and Cmax increased 3.1-fold and 2.2-fold, respectively. Dosage adjustment of temsirolimus to 12.5 mg/week in the presence of strong CYP3A4 inhibitors is expected to adjust levels to the range observed without inhibitors; however, there are no data available with this dose adjustment.(3)

Slt Inhibitors Of Bcrp With Myelosuppression/Cladribine Oral

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Inhibitors of BCRP may increase the absorption of cladribine.(1-2) Also, cladribine in combination with immunosuppressives and immune-modulators all suppress the immune system.(1-2)

CLINICAL EFFECTS: The concurrent administration of cladribine with an inhibitor of BCRP may result in elevated levels of cladribine and signs of toxicity.(1-2) Concurrent use of cladribine with immunosuppressive or immune-modulating agents may result in an increased risk of serious infections, such as disseminated herpetic infection or progressive multifocal leukoencephalopathy (PML), an opportunistic infection caused by the JC virus (JCV).(1-2)

PREDISPOSING FACTORS: Incomplete washout of previously prescribed immunosuppressive or immune-modulating medications.

PATIENT MANAGEMENT: The manufacturer of cladribine states concurrent use of BCRP inhibitors should be avoided during the 4- to 5-day cladribine treatment.(1-2) Selection of an alternative concurrent medication with no or minimal transporter inhibiting proprieties should be considered. If this is not possible, dose reduction to the minimum mandatory dose of the BCRP inhibitor, separation in timing of administration, and careful patient monitoring is recommended.(1-2) Myelosuppression risk recommendations for cladribine regarding this interaction differ between regulatory approving agencies. The cladribine US prescribing information states: -Concomitant use with myelosuppressive or other immunosuppressive drugs is not recommended. Acute short-term therapy with corticosteroids can be administered. In patients who have previously been treated with immunomodulatory or immunosuppressive drugs, consider potential additive effect, the mode of action, and duration of effect of the other drugs prior to initiation of cladribine.(1) The cladribine Canadian prescribing information states: -Use of cladribine in immunocompromised patients is contraindicated because of a risk of additive effects on the immune system. Acute short-term therapy with corticosteroids can be administered during cladribine treatment.(2) Monitor for signs of hematologic toxicity. Lymphocyte counts should be monitored.

DISCUSSION: Cladribine is a substrate of BCRP. Inhibitors of this transporter are expected to increase cladribine levels.(1-2) BCRP inhibitors linked to this monograph include: asciminib, belumosudil, cyclosporine, encorafenib, leflunomide, leniolisib, momelotinib, pirtobrutinib, and teriflunomide.(1,2) Fatal disseminated herpes zoster and herpes simplex infections and cases of progressive multifocal leukoencephalopathy (PML) have been reported in patients who previously received immunomodulators or immunosuppressants.(1-2)

Weak Cyp3a4 Inhibitors/Eliglustat

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Weak inhibitors of CYP3A4 may inhibit the metabolism of eliglustat. If the patient is also taking an inhibitor of CYP2D6, eliglustat metabolism can be further inhibited.(1)

CLINICAL EFFECTS: Concurrent use of an agent that is a weak inhibitor of CYP3A4 may result in elevated levels of and clinical effects of eliglustat, including prolongation of the PR, QTc, and/or QRS intervals, which may result in life-threatening cardiac arrhythmias.(1)

PREDISPOSING FACTORS: If the patient is also taking an inhibitor of CYP2D6, is a poor metabolizer of CYP2D6, and/or has hepatic impairment, eliglustat metabolism can be further inhibited.(1) The risk of QT prolongation or torsades de pointes may be increased in patients with cardiovascular disease (e.g. heart failure, myocardial infarction, history of torsades de pointes, congenital long QT syndrome), hypokalemia, hypomagnesemia, hypocalcemia, bradycardia, female gender, or advanced age.(2) Concurrent use of more than one drug known to cause QT prolongation or higher systemic concentrations of either QT prolonging drug are additional risk factors for torsades de pointes. Factors which may increase systemic drug concentrations include rapid infusion of an intravenous dose or impaired metabolism or elimination of the drug (e.g. coadministration with an agent which inhibits its metabolism or elimination, genetic impairment in drug metabolism or elimination, and/or renal/hepatic dysfunction).(2)

PATIENT MANAGEMENT: The concurrent use of eliglustat with weak inhibitors of CYP3A4 in poor metabolizers of CYP2D6 should be avoided.(1) The dosage of eliglustat with weak inhibitors of CYP3A4 in extensive metabolizers of CYP2D6 with mild (Child-Pugh Class A) hepatic impairment should be limited to 84 mg daily.(1) If concurrent therapy is warranted, consider obtaining serum calcium, magnesium, and potassium levels and monitoring ECG at baseline and at regular intervals. Correct any electrolyte abnormalities. Instruct patients to report any irregular heartbeat, dizziness, or fainting. For patients on avapritinib: this interaction applies only to gastrointestinal stromal tumor (GIST) patients on avapritinib 200 mg or 300 mg.(3)

DISCUSSION: Ketoconazole (400 mg daily), a strong inhibitor of CYP3A4, increased eliglustat (84 mg BID) maximum concentration (Cmax) and area-under-curve (AUC) by 4-fold and 4.4-fold, respectively, in extensive metabolizers. Physiologically-based pharmacokinetic (PKPB) models suggested ketoconazole would increase eliglustat Cmax and AUC by 4.4-fold and 5.4-fold, respectively, in intermediate metabolizers. PKPB models suggested ketoconazole may increase the Cmax and AUC of eliglustat (84 mg daily) by 4.3-fold and 6.2-fold, respectively, in poor metabolizers.(1) PKPB models suggested fluconazole, a moderate inhibitor of CYP3A4, would increase eliglustat Cmax and AUC by 2.8-fold and 3.2-fold, respectively, in extensive metabolizers and by 2.5-fold and 2.9-fold, respectively in intermediate metabolizers. PKPB models suggest that concurrent eliglustat (84 mg BID), paroxetine (a strong inhibitor of CYP2D6), and ketoconazole would increase eliglustat Cmax and AUC by 16.7-fold and 24.2-fold, respectively, in extensive metabolizers. In intermediate metabolizers, eliglustat Cmax and AUC would be expected to increase 7.5-fold and 9.8-fold, respectively.(1) PKPB models suggest that concurrent eliglustat (84 mg BID), terbinafine (a moderate inhibitor of CYP2D6), and ketoconazole would increase eliglustat Cmax and AUC by 10.2-fold and 13.6-fold, respectively, in extensive metabolizers. In intermediate metabolizers, eliglustat Cmax and AUC would be expected to increase 4.2-fold and 5-fold, respectively.(1) Weak inhibitors of CYP3A4 include: amlodipine, anamorelin, asciminib, avapritinib, azithromycin, Baikal skullcap, belumosudil, berberine, bicalutamide, blueberry, brodalumab, camizestrant, cannabidiol, chlorzoxazone, cilostazol, cimetidine, ciprofloxacin, clotrimazole, cranberry, cyclosporine, daclatasvir, daridorexant, delavirdine, dihydroberberine, diosmin, elinzanetant, everolimus, flibanserin, fosaprepitant, fostamatinib, gepotidacin, ginkgo, givinostat, glecaprevir/pibrentasvir, goldenseal, grazoprevir, isoniazid, istradefylline, ivacaftor, lacidipine, lapatinib, larotrectinib, lazertinib, leflunomide, levamlodipine, linagliptin, lomitapide, lurasidone, olaparib, osilodrostat, palbociclib, pazopanib, peppermint oil, piperine, propiverine, propofol, ranolazine, resveratrol, roxithromycin, rucaparib, selpercatinib, simeprevir, sitaxsentan, skullcap, teriflunomide, ticagrelor, tolvaptan, trofinetide, vepdegestrant, vonoprazan, and ziftomenib.(4,5)

Weak Cyp3a4 Inhibitors/Lomitapide

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Weak inhibitors of CYP3A4 may inhibit the metabolism of lomitapide.(1) Lomitapide is very susceptible to CYP3A4 inhibition. For example, in an interaction study with a strong CYP3A4 inhibitor (ketoconazole) lomitapide exposure was increased 27-fold.(2) Thus even weak CYP3A4 inhibitors may affect lomitapide exposure (AUC, area-under-curve).

CLINICAL EFFECTS: Concurrent use of a weak inhibitor of CYP3A4 may result in 2-fold increases in lomitapide levels and toxicity from lomitapide.(1)

PREDISPOSING FACTORS: This interaction may be more severe in patients with hepatic impairment or with end-stage renal disease.(1)

PATIENT MANAGEMENT: When initiating lomitapide in patients taking a stable dose of a weak CYP3A4 inhibitor, follow the recommended dose and titration schedule per labeling. When initiating a weak CYP3A4 inhibitor in patients taking lomitapide, decrease the dose of lomitapide by 50%. The maximum recommended lomitapide dose with concurrent weak CYP3A4 inhibitors should be: -Adults (age 18 years and older): 30 mg daily, -Age group 11 to 17 years: 20 mg daily, -Age group 2 to 10 years: 10 mg daily. Due to lomitapide's long half-life, it may take 1 to 2 weeks to see the full effect of this interaction.(1) For patients on avapritinib: this interaction applies only to gastrointestinal stromal tumor (GIST) patients on avapritinib 200 mg or 300 mg.(2)

DISCUSSION: Lomitapide is very susceptible to CYP3A4 inhibition. For example, in an interaction study with a strong CYP3A4 inhibitor (ketoconazole) lomitapide exposure was increased 27-fold.(2) Based upon interactions with stronger inhibitors, weak inhibitors of CYP3A4 are predicted to increase lomitapide area-under-curve(AUC) 2-fold.(1) Weak CYP3A4 inhibitors linked to this interaction include: amiodarone, amlodipine, anamorelin, asciminib, atorvastatin, avapritinib, azithromycin, Baikal skullcap, belumosudil, bicalutamide, blueberry juice, brodalumab, camizestrant, cannabidiol, capivasertib, cilostazol, cimetidine, ciprofloxacin, chlorzoxazone, clotrimazole, cranberry juice, cyclosporine, daridorexant, delavirdine, diosmin, elinzanetant, everolimus, flibanserin, fosaprepitant, fostamatinib, gepotidacin, ginkgo, givinostat, glecaprevir/pibrentasvir, goldenseal, grazoprevir, isoniazid, istradefylline, ivacaftor, lacidipine, lapatinib, larotrectinib, lazertinib, leflunomide, levamlodipine, linagliptin, lurasidone, maribavir, mavorixafor, olaparib, osilodrostat, palbociclib, pazopanib, peppermint oil, piperine, propiverine, propofol, ranitidine, ranolazine, resveratrol, roxithromycin, rucaparib, selpercatinib, sevabertinib, sitaxsentan, skullcap, teriflunomide, ticagrelor, tolvaptan, trofinetide, vepdegestrant, viloxazine, vonoprazan, ziftomenib, and zileuton.(1-3)

Weak Cyp3a4 Inhibitors/Pimozide

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Weak inhibitors of CYP3A4 may inhibit the metabolism of pimozide.(1,2)

CLINICAL EFFECTS: Concurrent use with weak CYP3A4 inhibitors may increase the levels and effects of pimozide including QTc prolongation and potentially life-threatening cardiac arrhythmias like torsades de pointes.(1-2) Concurrent use may also result in extrapyramidal symptoms such as akathisia, bradykinesia, cogwheel rigidity, dystonia, hypertonia, and oculogyric crisis.(1)

PREDISPOSING FACTORS: The risk of QT prolongation or torsades de pointes may be increased in patients with cardiovascular disease (e.g. heart failure, myocardial infarction, history of torsades de pointes, congenital long QT syndrome), hypokalemia, hypomagnesemia, hypocalcemia, bradycardia, female gender, or advanced age.(3) Concurrent use of more than one drug known to cause QT prolongation or higher systemic concentrations of either QT prolonging drug are additional risk factors for torsades de pointes. Factors which may increased systemic drug concentrations include rapid infusion of an intravenous dose or impaired metabolism or elimination of the drug (e.g. coadministration with an agent which inhibits its metabolism or elimination, genetic impairment in drug metabolism or elimination, and/or renal/hepatic dysfunction).(3) The risk of anticholinergic toxicities including cognitive decline, delirium, falls and fractures is increased in geriatric patients using more than one medicine with anticholinergic properties.(4)

PATIENT MANAGEMENT: The US manufacturer of pimozide states that concomitant treatment with strong CYP3A4 inhibitors is contraindicated and treatment with less potent inhibitors of CYP3A4 should also be avoided.(1) The UK manufacturer of pimozide contraindicates concomitant use of pimozide with CYP3A4 inhibitors and CYP2D6 inhibitors, stating that inhibition of either or both CYP3A4 and CYP2D6 may result in the elevation of pimozide blood concentration and increase the possibility of QT-prolongation.(2) For patients on avapritinib: this interaction applies only to gastrointestinal stromal tumor (GIST) patients on avapritinib 200 mg or 300 mg.(5) If concurrent use cannot be avoided, then correct or minimize QT prolonging risk factors, use the lowest effective dose of pimozide, and discontinue other concurrent QT prolonging agents or CYP3A4 or CYP2D6 inhibitors if possible. If concurrent therapy is warranted, consider obtaining serum calcium, magnesium, and potassium levels and monitoring ECG at baseline and at regular intervals. Correct any electrolyte abnormalities. Instruct patients to report any irregular heartbeat, dizziness, or fainting.

DISCUSSION: Pimozide is metabolized at CYP3A.(1,5) Elevated levels of pimozide may prolong the QTc interval resulting in life-threatening ventricular arrhythmias.(1) Serious cardiovascular events, including QT prolongation, torsades de pointes, ventricular tachycardia, cardiac arrest, and/or sudden death have been reported in patients taking pimozide in combination with itraconazole and/or other CYP3A4 inhibitors.(1,2) Weak CYP3A4 inhibitors include: amlodipine, asciminib, avapritinib, belumosudil, berberine, bicalutamide, blueberry, brodalumab, camizestrant, cannabidiol, capivasertib, chlorzoxazone, cimetidine, clotrimazole, cranberry, cyclosporine, daclatasvir, daridorexant, dihydroberberine, diosmin, elinzanetant, everolimus, flibanserin, fostamatinib, ginkgo, glecaprevir/pibrentasvir, goldenseal, grazoprevir, isoniazid, istradefylline, ivacaftor, lacidipine, larotrectinib, lazertinib, leflunomide, levamlodipine, linagliptin, lomitapide, lurasidone, marijuana, olaparib, palbociclib, peppermint, piperine, pirtobrutinib, propiverine, ranitidine, resveratrol, scutellarin, sevabertinib, simeprevir, sitaxsentan, teriflunomide, ticagrelor, tolvaptan, trofinetide, viloxazine, and vonoprazan.(7,8)

Moderate Interaction: Assess the risk to the patient and take action as needed.

Cyclosporine/Ambrisentan (<=5 MG)

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Cyclosporine may inhibit the metabolism/transport of ambrisentan by CYP3A4, OATP, and P-gp.(1,2)

CLINICAL EFFECTS: Concurrent use of cyclosporine may result in elevated levels of and toxicity from ambrisentan.(1,2)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Patients maintained on cyclosporine should receive a maximum daily dose of 5 mg of ambrisentan.(1,2)

DISCUSSION: In an open-label, parallel-treatment study, 28 healthy subjects had ambrisentan (5 mg daily) added to steady-state cyclosporine (100-150 mg BID) and 24 subjects had cyclosporine (100-150 mg BID) added to steady-state ambrisentan (5 mg daily). All drug levels were evaluated at steady-state. Ambrisentan maximum concentration (Cmax) and area-under-curve (AUC) increased 1.5-fold and 2-fold, respectively, in the presence of cyclosporine. There were no significant effects on cyclosporine levels. The addition of ambrisentan to cyclosporine was less tolerable than the addition of cyclosporine to ambrisentan therapy.(1,2)

Cyclosporine/Amiodarone

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Amiodarone may inhibit the metabolism of cyclosporine by CYP3A4.

CLINICAL EFFECTS: Increased levels of cyclosporine, which may result in renal toxicity.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Monitor cyclosporine levels and renal function in patients receiving concurrent therapy. During concurrent therapy with amiodarone, cyclosporine dosages may need to be decreased by over 50%.

DISCUSSION: Documentation on this interaction is limited to case reports involving ten transplant patients. In the first report, the dosage of cyclosporine required to maintain a therapeutic trough concentration of 200-250 ng/ml (measured by high-performance liquid chromatography) decreased from 5.4-5.8 mg/Kg/day to 2.3 mg/Kg/day following the addition of amiodarone. Cyclosporine clearance decreased from 0.22 L/hr/Kg to 0.1 L/hr/Kg 12 days after the addition of amiodarone. In the second report, there was a twofold increase in cyclosporine levels following the addition of amiodarone to stabilized cyclosporine therapy. A retrospective study of eight transplant patients who received concurrent therapy with cyclosporine and amiodarone reported that cyclosporine levels increased in all subjects despite a decrease in cyclosporine dosage (from 6.2 mg/Kg/day to 3.5 mg/Kg/day).

Cyclosporine/Calcium Channel Blockers

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Calcium channel blockers may inhibit the metabolism of cyclosporine by CYP3A4.

CLINICAL EFFECTS: Concurrent use of calcium channel blockers may result in elevated levels of and toxicity from cyclosporine.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Monitor cyclosporine levels when initiating or discontinuing calcium channel blockers.

DISCUSSION: Concurrent administration of cyclosporine and amlodipine, diltiazem, nicardipine, or verapamil has caused elevated cyclosporine levels. Renal toxicity was seen in some cases. Upon discontinuation of the calcium channel blocker, cyclosporine concentrations have returned to baseline levels. With concurrent diltiazem administration, cyclosporine dosage decreases of 15% to 48% were required. A prospective study in 11 renal transplant patients showed a 40% increase in trough cyclosporine levels when given concomitantly with amlodipine.(29)

Cyclosporine/Colesevelam

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Colesevelam may bind to cyclosporine in the gastrointestinal track, preventing its absorption.(1)

CLINICAL EFFECTS: Simultaneous administration of colesevelam may result in decreased levels and effectiveness of cyclosporine.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Cyclosporine should be administered four hours before colesevelam. Monitor cyclosporine levels in patients receiving concurrent therapy and adjust as necessary.(1)

DISCUSSION: When administered with colesevelam (3.75 g), the area-under-curve (AUC) and maximum concentration (Cmax) of cyclosporine (200 mg) decreased by 34% and by 44%, respectively.(1)

Cyclosporine/Ezetimibe

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: The exact mechanism is unknown.

CLINICAL EFFECTS: Concurrent use of cyclosporine with ezetimibe may result in elevated levels of and side effects from ezetimibe and cyclosporine.(1)

PREDISPOSING FACTORS: Patients with severe renal insufficiency may experience larger increases in ezetimibe levels.(1)

PATIENT MANAGEMENT: Carefully weigh the risk of elevated levels of ezetimibe and cyclosporine against benefits of ezetimibe in patients maintained on cyclosporine. Patients receiving concurrent therapy should be monitored for adverse effects. Ezetimibe may need to be discontinued.(1)

DISCUSSION: In a study in 8 post-renal transplant patients with mildly impaired or normal renal function (CrCL greater than 50ml/min), stable cyclosporine doses (75 to 150 mg twice daily) increased ezetimibe area-under-curve (AUC) and maximum concentration (Cmax) values by 240% and by 290%, respectively, compared to historical healthy controls. In another study, a renal transplant patient with severe renal impairment (CrCl = 13.2) maintained on cyclosporine experienced a 12-fold greater exposure to ezetimibe than healthy subjects.(1) In a study in 12 healthy subjects, ezetimibe (20 mg daily for 8 days) increased the AUC of a single dose of cyclosporine (100 mg) by 15%.(1)

Cyclosporine/Fluva(<=20MG BID);Prava(<=20MG);Rosuva(<=5MG)

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Cyclosporine is a CYP3A4, P-glycoprotein, and OATP inhibitor, while statins are CYP3A4, P-glycoprotein, and OATP substrates. (1,2) When a statin is combined with cyclosporine, statin clearance is reduced and elevated statin concentrations remain in the peripheral blood and muscle cells.(3)

CLINICAL EFFECTS: Myopathy and muscle aches, tenderness and weakness (rhabdomyolysis) may occur with concurrent administration of HMG-CoA reductase inhibitors and cyclosporine.

PREDISPOSING FACTORS: The risk for myopathy or rhabdomyolysis may be greater in patients 65 years and older, inadequately treated hypothyroidism, renal impairment, carnitine deficiency, malignant hyperthermia, or in patients with a history of myopathy or rhabdomyolysis. Patients with a SLCO1B1 polymorphism that leads to decreased function of the hepatic uptake transporter OATP1B1 may have increased statin concentrations and be predisposed to myopathy or rhabdomyolysis. Patients on rosuvastatin with ABCG2 polymorphisms leading to decreased or poor BCRP transporter function may have increased rosuvastatin concentrations and risk of myopathy. Patients on fluvastatin who are CYP2C9 intermediate or poor metabolizers may have increased fluvastatin concentrations and risk of myopathy.

PATIENT MANAGEMENT: The dosage of fluvastatin should not exceed 20 mg BID in patients receiving cyclosporine.(4) The dosage of pravastatin should not exceed 20 mg in patients receiving cyclosporine.(5) The dosage of rosuvastatin should not exceed 5 mg in patients receiving cyclosporine.(6) Patients receiving concurrent therapy should be instructed to report symptoms of muscle pain, tenderness, or weakness.

DISCUSSION: Since this reaction may occur with HMG-CoA-reductase inhibitors alone, a causal relationship is difficult to establish. However, the incidence of myopathy and rhabdomyolysis appears to increase with concurrent administration of cyclosporine. In a study, administration of pravastatin in 11 heart transplant patients receiving cyclosporine was compared to 8 control subjects not receiving cyclosporine. Pravastatin AUC and Cmax were 7-8-fold and 12-fold higher, respectively, in subjects taking cyclosporine.(7) In a double-blind, randomized, cross-over study in 44 renal transplant patients, neither lovastatin nor pravastatin affected cyclosporine levels. Pravastatin levels after 1 day and after 28 days of concurrent therapy were 5-fold higher than historical controls. Lovastatin levels accumulated over the course of the study and by Day 28 were 20-fold higher than historical controls.(8) In a study in 31 renal transplant patients, neither pravastatin nor simvastatin affected cyclosporine levels.(9) In contrast, in a study in 44 heart transplant subjects, cyclosporine clearance was increased following the addition of simvastatin.(10) In a study, a single dose of cyclosporine (5 mg/kg) increased the Cmax and AUC of a single dose of pravastatin (40 mg) by 327% and 282%, respectively.(6) Several studies have found no effect from fluvastatin on cyclosporine pharmacokinetics.(11-15) One of these also noted no affects of cyclosporine on fluvastatin levels.(11) In contrast, a study that compared the administration of fluvastatin in 10 heart transplant to 10 healthy control subjects found that fluvastatin AUC and Cmax were 2.55-fold and 3.10-fold higher than in control subjects.(16) In another study, stable cyclosporine doses increased the Cmax and AUC of fluvastatin (20 mg daily for 14 weeks) by 30% and 90%, respectively.(4) In an open-label study in 10 heart transplant patients, concurrent cyclosporine increased rosuvastatin AUC and Cmax by 7.1-fold and 10.6-fold, respectively, when compared to historical controls. There were no effects on cyclosporine levels.(7,17)

Cyclosporine/Lenacapavir

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Lenacapavir may inhibit the metabolism of cyclosporine by CYP3A4.

CLINICAL EFFECTS: Concurrent use of lenacapavir may result in elevated levels of and toxicity from cyclosporine.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Monitor cyclosporine levels and kidney function in patients in whom lenacapavir is initiated, adjusted, or discontinued. The dosage of cyclosporine may need to be adjusted or lenacapavir may need to be discontinued.

DISCUSSION: In a study, simultaneous administration of midazolam (2.5 mg single dose) with lenacapavir resulted in an increase in the maximum concentration (Cmax) and area-under-the-curve (AUC) of midazolam by 1.94-fold and 3.59 fold and 1-hydroxymidazolam of 0.54-fold and 0.76-fold. Administration of midazolam (2.5 mg single dose) one day after lenacapavir resulted in an increase in Cmax and AUC of 2.16-fold and 4.08 fold and 1-hydroxymidazolam of 0.52-fold and 0.84-fold.

Cyclosporine/Nefazodone

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Nefazodone may inhibit the metabolism of cyclosporine by CYP3A4.

CLINICAL EFFECTS: Concurrent use of nefazodone may result in elevated levels of and toxicity from cyclosporine.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Monitor cyclosporine levels and kidney function in patients in whom nefazodone is initiated, adjusted, or discontinued. The dosage of cyclosporine may need to be adjusted or nefazodone may need to be discontinued.

DISCUSSION: In a case report, cyclosporine (225 mg twice daily) levels increased 70% 3 days following the addition of nefazodone (25 mg twice daily) the regimen of a 23 year-old male kidney transplant patient.(1) In a case report, cyclosporine (200 mg twice daily) levels increased 1.67-fold following the addition of nefazodone (100 mg twice daily) to the regimen of a 50 year-old male kidney transplant patient. The patient also developed tremors, headaches, and increased blood pressure. The cyclosporine dose was reduced 50% and levels returned to baseline.(2) In a case report, cyclosporine (130 mg twice daily) levels increased from the low 100's to 775 ng/ml within 2 weeks of initiating nefazodone (150 mg twice daily) in a 58 year-old female cardiac transplant patient.(3)

Cyclosporine/Octreotide

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Octreotide may interfere with the enterohepatic circulation of cyclosporine or may delay or inhibit the absorption of cyclosporine.(2)

CLINICAL EFFECTS: The concurrent administration of octreotide and cyclosporine may result in a decrease in cyclosporine levels.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Cyclosporine levels should be monitored in patients receiving concurrent therapy with cyclosporine and octreotide. The dosage of cyclosporine may need to be adjusted if octreotide is added to or discontinued from cyclosporine therapy. Octreotide may need to be discontinued.

DISCUSSION: In a study, 23 of 65 pancreas transplant patients were treated octreotide. During octreotide therapy, the dosage of oral cyclosporine required to maintain therapeutic levels increased. In addition 15 patients required supplemental intravenous cyclosporine to maintain cyclosporine levels.(2) In a case report, a cadaver renal and whole-pancreas transplant recipient was treated for a fistula with octreotide. Cyclosporine blood levels slowly decreased despite an increase in cyclosporine dosage (from 180 mg to 300 mg daily). When the cyclosporine level decreased below 100 ng/ml, intravenous cyclosporine was administered. Octreotide was discontinued when the patient developed graft rejection. Cyclosporine levels returned to baseline and the rejection was reversed.(1) In another case report, cyclosporine levels dropped below detection when octreotide was added to his therapy. The patient was successfully treated for graft rejection and octreotide was discontinued.(3) These authors reported a total of nine patients in whom cyclosporine levels decreased following the addition of octreotide to cyclosporine.(4) In a study of 10 patients with severe diarrhea following bone marrow transplantation, cyclosporine dosage requirements increased by 50% in two subjects following the addition of octreotide.(5)

Cyclosporine/P-Glycoprotein (P-GP) Inhibitors

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: P-glycoprotein (P-gp) inhibitors may inhibit cellular efflux of cyclosporine.(1,2)

CLINICAL EFFECTS: Concurrent administration of a P-gp inhibitor may result in elevated levels and toxicities of cyclosporine, including serious infections, nephrotoxicity, and hepatotoxicity.(1,2)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Closely monitor cyclosporine levels during concurrent use with P-gp inhibitors. Cyclosporine dose adjustment may be needed to achieve desired concentrations.(1,2)

DISCUSSION: Cyclosporine is a known substrate of P-gp. Inhibitors of P-gp may increase toxicity of cyclosporine.(1,2) Inhibitors of P-gp linked to this monograph include: abrocitinib, deutivacaftor, imlunestrant, ivacaftor, and vepdegestrant.

Cyclosporine/Repaglinide

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Cyclosporine may inhibit the metabolism of repaglinide by CYP3A4 and OATP-mediated hepatic uptake of repaglinide.(1)

CLINICAL EFFECTS: Concurrent use with cyclosporine may result in increased levels of and effects from repaglinide, including hypoglycemia.(1,2)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Use caution when initiating repaglinide in patients maintained on cyclosporine.(1,2) Lower starting doses and careful titration may be required.(3) Monitor patients receiving concurrent therapy for signs of hypoglycemia.(1,2) The dose of repaglinide may need to be adjusted. The US manufacturer of repaglinide recommends the daily maximum dose should be limited to 6 mg and increased frequency of glucose monitoring may be required with concurrent therapy.(4)

DISCUSSION: In a study in 12 healthy males, cyclosporine (100 mg every 12 hours for 2 doses) increased the maximum concentration (Cmax) and area-under-curve (AUC) of a single dose of repaglinide (0.25 mg) by 1.8-fold (range 0.6-3.7-fold, p<0.001) and by 2.4-fold (range 1.2-5.3-fold, p<0.001).(1,2) The amount of unchanged repaglinide, its M2 metabolite, and its M4 metabolite excreted in the urine 2.7-fold, 7.5-fold, 5.0-fold, respectively. No statistically significant changes in blood glucose response were noted; however, individual responses correlated with the degree of increased repaglinide levels.(1)

Cyclosporine/Selected Fibrates

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Concurrent use of cyclosporine and fibrates may result in additive nephrotoxicity.(1)

CLINICAL EFFECTS: Concurrent use of cyclosporine and fibrates may result in additive nephrotoxicity.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Use concurrent cyclosporine and fibrates with caution. If concurrent use is warranted, use the lowest effective dose of the fibrate and monitor patients for decreased renal function.

DISCUSSION: In a study in heart-transplant patients, concurrent fenofibrate had no effect on cyclosporine levels, but patients developed increased serum concentration.(2) Two studies in transplant patients found that gemfibrozil had no effect on cyclosporine levels or renal function.(3,4)

Cyclosporine/Selected Moderate Cyp3a4 Inhibitors

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Moderate CYP3A4 inhibitors may inhibit the metabolism of cyclosporine.(1)

CLINICAL EFFECTS: Concurrent use of moderate CYP3A4 inhibitors may result in elevated levels of and toxicity from cyclosporine, including serious infections, nephrotoxicity, and hepatotoxicity.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: If cyclosporine is used with a moderate CYP3A4 inhibitor, dose adjustment of cyclosporine may be necessary to achieve the desired cyclosporine concentration.(1)

DISCUSSION: In a study, renal and cardiac patients required a cyclosporine dose reduction of 15% to 48% when diltiazem was co-administered to maintain a cyclosporine trough similar to cyclosporine alone.(2) In a study, cyclosporine required a 25% dose reduction when co-administered with fluconazole to maintain a goal serum concentration similar to cyclosporine alone.(3) Moderate inhibitors of CYP3A4 include: avacopan, berotralstat, clofazimine, duvelisib, fedratinib, fluvoxamine, oral lefamulin, netupitant, nilotinib, nirogacestat, rilzabrutinib, schisandra, stiripentol, tofisopam, and treosulfan.(4,5)

Cyclosporine/Selected Quinolones

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Cyclosporine and quinolones may result in synergistic nephrotoxicity.(1,2) Quinolones may inhibit the metabolism of cyclosporine and may interfere with the renal tubular excretion of cyclosporine.(2)

CLINICAL EFFECTS: Concurrent use of cyclosporine with quinolones may result in elevated levels of cyclosporine and nephrotoxicity.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Patients receiving concurrent therapy with cyclosporine and a quinolone should be monitored for increased cyclosporine levels and signs of nephrotoxicity.

DISCUSSION: Nephrotoxicity with(1) and without(2) elevated cyclosporine levels has been reported in patients maintained in cyclosporine in whom ciprofloxacin was initiated. A retrospective review found a significantly greater percentage of cases of biopsy-proven rejection in patients who received concurrent cyclosporine and ciprofloxacin (45%) than in matched controls who did not receive ciprofloxacin (19%).(3) In contrast to these reports, three studies found no effect on cyclosporine levels or rates of nephrotoxicity with concurrent ciprofloxacin.(4-6) In a study in 12 healthy subjects, levofloxacin had no effect on the pharmacokinetics of a single dose of cyclosporine.(7) In a study in pediatric patients, the dose of cyclosporine needed to maintain cyclosporine trough levels between 150 ng/ml and 400 ng/ml was found to be 4.5 mg/kg/day in patients receiving concurrent norfloxacin and 7.4 mg/kg/day in patients not receiving norfloxacin.(8) Elevated levels of cyclosporine were noted in a patient following the addition of norfloxacin to his cyclosporine regimen.(9)

Cyclosporine/Sirolimus; Temsirolimus

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: The exact mechanism is unknown. Temsirolimus is a pro-drug of sirolimus.(1)

CLINICAL EFFECTS: The concurrent administration of sirolimus and cyclosporine may result in elevated levels of sirolimus and cyclosporine. Elevated levels of sirolimus may be seen as soon as after one concurrent dose. Elevated levels of cyclosporine may take several weeks to develop.(2) Sirolimus may increase the risk of calcineurin-induced hemolytic uremic syndrome/thrombotic thrombocytopenic purpura/thrombotic microangiopathy.(2) In liver transplant patients, concurrent sirolimus and cyclosporine has been associated with an increase in hepatic artery thrombosis (HAT). Most cases occurred within 30 days post-transplantation and most led to graft loss or death.(2)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of sirolimus recommends that sirolimus be administered four hours after cyclosporine oral solution (MODIFIED) and cyclosporine capsules (MODIFIED).(2) Blood levels of sirolimus and cyclosporine and renal function should be carefully monitored in patients receiving concurrent therapy with these agents. The dosages of one or both both agents may need to be adjusted. The manufacturer of sirolimus recommends that sirolimus not be used in liver transplant patients.(2) The US manufacturer of sirolimus protein-bound injection (Fyarro) states a dose reduction to 56 mg/m2 is recommended when used concurrently with moderate or weak CYP3A4 inhibitors. Concurrent use with strong CYP3A4 inhibitors should be avoided.(3) Since temsirolimus is a pro-drug of sirolimus, it would be prudent to monitor cyclosporine levels during concurrent therapy.

DISCUSSION: In a single dose study in 24 healthy subjects, simultaneous administration of sirolimus oral solution (10 mg) and cyclosporine capsules (300 mg, MODIFIED) resulted in increases in the sirolimus maximum concentration (Cmax) and area-under-curve (AUC) by 116% and 230%, respectively. Sirolimus four hours after the administration of cyclosporine capsules (MODIFIED) resulted in increases in sirolimus Cmax and AUC by 37% and 80%, respectively. Cyclosporine Cmax and AUC were initially not significantly affected; however, after multiple doses, the clearance of cyclosporine was decreased and lower doses of cyclosporine were required.(2) In a single dose study in 24 healthy subjects, simultaneous administration of sirolimus tablets (10 mg) and cyclosporine capsules (300 mg) resulted in increases of sirolimus Cmax and AUC by 512% and 148%, respectively. Sirolimus four hours after the administration of cyclosporine capsules resulted in increases of only 33%. (2) In a single dose cross-over study in 33 healthy subjects, sirolimus (5 mg) was administered alone, 2 hours before cyclosporine capsules (300 mg, MODIFIED), and 2 hours after cyclosporine capsules (300 mg, MODIFIED). There was no significant difference in sirolimus Cmax and AUC when administered 2 hours before cyclosporine; however, sirolimus Cmax and AUC increased by 126% and 141%, respectively, when given 2 hours after cyclosporine.(2) The concurrent administration of sirolimus and cyclosporine oral solution resulted in increases in sirolimus trough concentrations by 67%-86%. There was no significant effect on cyclosporine concentrations.(2)

Cyclosporine/Tigecycline

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: The mechanism of the interaction is unknown but may be related to competitive inhibition of P-glycoprotein-mediated biliary excretion of tigecycline and cyclosporine.(1)

CLINICAL EFFECTS: Concurrent use of tigecycline may result in elevated levels of and toxicity from cyclosporine, including nephrotoxicity.(2,3)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Monitor cyclosporine levels during and after therapy with tigecycline. The dosage of cyclosporine may need to be adjusted.(2,3)

DISCUSSION: A 61-year-old renal transplant recipient on cyclosporine 120 mg daily was started on intravenous tigecycline for a urinary tract infection. Cyclosporine levels and serum creatinine rose markedly and the dose of cyclosporine was reduced by 50%. After tigecycline was discontinued for 3 days, the dose of cyclosporine had to be increased back to 120 mg daily to maintain therapeutic levels.(4)

Cyclosporine; Sirolimus/Metoclopramide

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: The exact mechanism is unknown but is possibly due to a metoclopramide-induced increase in gastric emptying time leading to an increase in cyclosporine absorption.(1)

CLINICAL EFFECTS: The pharmacological and toxic effects of cyclosporine and sirolimus may be increased.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Monitor serum cyclosporine or sirolimus concentrations and adjust dose as necessary.

DISCUSSION: In a study involving 14 renal transplant patients, a single oral dose of metoclopramide 20 mg produced nearly a 30% increase in cyclosporine bioavailability.(2,3) Similar results were reported in a patient receiving cyclosporine and metoclopramide concurrently.(4) Additional studies with varying dosage schedules of metoclopramide administration are needed to determine the extent of this interaction.

Dual Cyp3a4 & P-Gp Inhibitors/Nintedanib

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Nintedanib is a substrate for the P-glycoprotein (P-gp) transporter and is metabolized to a minor extent by CYP3A4.

CLINICAL EFFECTS: Concurrent use of an agent that is both an inhibitor of P-gp and CYP3A4 may result in elevated levels of and clinical effects of nintedanib.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of nintedanib recommends close monitoring for nintedanib patients receiving drugs which are both P-gp and CYP3A4 inhibitors. In an interaction study ketoconazole increased exposure to nintedanib by 60%. Nintedanib therapy may need to be interrupted or the dose may need to be reduced.(1)

DISCUSSION: In an interaction study coadministration with ketoconazole, a P-gp and CYP3A4 inhibitor, increased nintedanib exposure (area-under-curve, AUC) and maximum concentration (Cmax) by 1.61-fold and 1.83 fold respectively.(1) Strong CYP3A4 & P-gp inhibitors include: adagrasib, boceprevir, clarithromycin, cobicistat, grapefruit, indinavir, itraconazole, josamycin, ketoconazole, levoketoconazole, lonafarnib, lopinavir, mibefradil, mifepristone, nefazodone, nelfinavir, nirmatrelvir, paritaprevir, posaconazole, ritonavir, saquinavir, telaprevir, telithromycin, tipranavir, and tucatinib. Moderate CYP3A4 & P-gp inhibitors include: conivaptan, diltiazem, dronedarone, erythromycin, fluvoxamine, isavuconazonium, schisandra, and verapamil. Weak CYP3A4 & P-gp inhibitors include: amiodarone, azithromycin, cimetidine, cyclosporine, daclatasvir, daridorexant, diosmin, flibanserin, fluvoxamine, fostamatinib, glecaprevir/pibrentasvir, ivacaftor, lapatinib, mavorixafor, ranolazine, and vepdegestrant.(2)

Immunosuppressives; Immunomodulators/Cladribine Oncology Inj

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Cladribine in combination with immunosuppressives and immune-modulators all suppress the immune system.(1-4)

CLINICAL EFFECTS: Concurrent use of cladribine with immunosuppressive or immune-modulating agents may result in an increased risk of serious infections.(1-4)

PREDISPOSING FACTORS: Incomplete washout of previously prescribed immunosuppressive or immune-modulating medications.

PATIENT MANAGEMENT: Recommendations for cladribine regarding this interaction differ between regulatory approving agencies. The cladribine US, UK, and Australian prescribing information state: -Caution should be exercised if cladribine injection is administered before, after, or in conjunction with other drugs known to cause immunosuppression or myelosuppression.(1-3) The cladribine Canadian prescribing information states: -Proceed carefully in patients with severe bone marrow impairment of any etiology since further suppression of bone marrow function should be anticipated.(4)

DISCUSSION: Severe bone marrow suppression, including neutropenia, anemia and thrombocytopenia, has been commonly observed in patients treated with cladribine injection, especially at high doses.(1-4)

Immunosuppressives; Immunomodulators/Covid-19 Vaccines

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Immunosuppressants and immunomodulators may prevent the immune system from properly responding to the COVID-19 vaccine.(1-3)

CLINICAL EFFECTS: Administration of a COVID-19 vaccine with immunosuppressants or immunomodulators may interfere with vaccine-induced immune response and impair the efficacy of the vaccine. However, patients should be offered and given a COVID-19 vaccine even if the use and timing of immunosuppressive agents cannot be adjusted.(1-3)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The Centers for Disease Control and Prevention (CDC),(1) Infectious Diseases Society of America (IDSA),(2) and the American College of Rheumatology (ACR)(3) have published guidances for COVID-19 vaccination in patients on immunosuppressants. The CDC states that all immunocompromised patients over 6 months of age should receive at least 1 dose of COVID-19 vaccine if eligible. See the CDC's Interim Clinical Considerations for Use of COVID-19 Vaccines for specific recommendations based on age, vaccination history, and vaccine manufacturer.(1) The CDC advises planning for vaccination at least 2 weeks before starting or resuming immunosuppressive therapy.(1) IDSA recommends timing COVID-19 vaccination at least 2 weeks before starting or at least 3 months after completing immunosuppressive therapy.(2) The ACR states that in general, immunosuppressants and immunomodulators should be held for 1-2 weeks after each vaccine dose.(3) Patients should be offered and given a COVID-19 vaccine even if the use and timing of immunosuppressive agents cannot be adjusted, though the immune response will likely be blunted. COVID-19 vaccines should not be delayed in patients taking immunosuppressive therapies.(1-2) See below for specific recommendations for certain agents. B-cell depleting agents, including rituximab: The CDC states that the utility of B-cell quantification to guide clinical care is not known and is not recommended. Patients who receive B-cell depleting therapy on a continuing basis should receive COVID-19 vaccines about 4 weeks before the next scheduled dose. For patients who received 1 or more doses of COVID-19 vaccine during treatment with B-cell-depleting therapies that were administered over a limited period (e.g., as part of a treatment regimen for certain malignancies), revaccination may be considered according to the current CDC recommendations for unvaccinated patients. The suggested interval to start revaccination is about 6 months after completion of the B-cell-depleting therapy.(1) IDSA recommends waiting for at least 3-6 months after the last infusion of B-cell depleting therapy before administering COVID-19 vaccines.(2) The ACR recommends consulting with the rheumatologist to determine optimal timing of COVID-19 vaccination. Measuring CD19 B cells may be considered to determine need for a booster vaccine dose. If B cell levels are not measured, a supplemental vaccine dose 2-4 weeks before the next scheduled dose of rituximab is recommended.(3) Recipients of hematopoietic cell transplant or CAR-T-cell therapy who received one or more doses of COVID-19 vaccine prior to or during treatment should undergo revaccination following the current CDC recommendations for unvaccinated patients. Revaccination should start at least 3 months (12 weeks) after transplant or CAR-T-cell therapy.(1,2) The CDC includes abatacept, cyclophosphamide, and TNF-alpha and cytokine inhibitors in their general recommendation to hold therapy for at least 2 weeks following vaccination (1) while the ACR provides different recommendations:(3) *Abatacept: - Subcutaneous abatacept should be withheld for 1-2 weeks after each vaccine dose, as disease activity allows. - For intravenous abatacept, time administration so that vaccination will occur 1 week before the next abatacept infusion. *Cyclophosphamide: When feasible, administer cyclophosphamide 1 week after each COVID-19 vaccine dose. *TNF-alpha inhibitors and cytokine inhibitors: The ACR was not able to reach consensus on whether to modify dosing or timing of these agents with COVID-19 vaccination.

DISCUSSION: IDSA recommendations are based on cohort and case control studies in immunocompromised patients that found low to modest vaccine effectiveness (37-61%) but lower risks of COVID-19 association hospitalization, COVID-19 related mortality, and critical illness.(2) The ACR convened a COVID-19 Vaccine Guidance Task Force to provide guidance on optimal use of COVID-19 vaccines in rheumatology patients. These recommendations are based on limited clinical evidence of COVID-19 vaccines in patients without rheumatic and musculoskeletal disorders and evidence of other vaccines in this patient population.(3) The ACR recommendation for rituximab is based on studies of humoral immunity following receipt of other vaccines. These studies have uncertain generalizability to vaccination against COVID-19, as it is unknown if efficacy is attributable to induction of host T cells versus B cell (antibody-based) immunity.(3) The ACR recommendation for mycophenolate is based on preexisting data of mycophenolate on non-COVID-19 vaccine immunogenicity. Emerging data suggests that mycophenolate may impair SARS-CoV-2 vaccine response in rheumatic and musculoskeletal disease and transplant patients.(3) The ACR recommendation for methotrexate is based on data from influenza vaccines and pneumococcal vaccines with methotrexate.(3) The ACR recommendation for JAK inhibitors is based on concerns related to the effects of JAK inhibitors on interferon signaling that may result in a diminished vaccine response.(3) The ACR recommendation for subcutaneous abatacept is based on several studies suggesting a negative effect of abatacept on vaccine immunogenicity. The first vaccine dose primes naive T cells, naive T cell priming is inhibited by CTLA-4, and abatacept is a CTLA-4Ig construct. CTLA-4 should not inhibit boosts of already primed T cells at the time of the second vaccine dose.(3)

Immunosuppressives; Immunomodulators/Sarilumab

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Sarilumab, immunosuppressives, and immunomodulators all suppress the immune system.(1)

CLINICAL EFFECTS: Concurrent use of sarilumab with immunosuppressive or immunomodulating agents may result in an increased risk for serious infections.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of sarilumab recommends caution because the concurrent use of sarilumab with immunosuppressive agents may increase the risk of infection. If concurrent therapy is warranted, consider the risk of additive immune suppression and monitor based on prescribing information for both agents.(1)

DISCUSSION: Sarilumab was studied as monotherapy and in combination with methotrexate or conventional disease modifying antirheumatic drugs (DMARDs) in rheumatoid arthritis studies. Sarilumab has not been studied with biological DMARDs and concurrent use should be avoided. If concurrent therapy is warranted, consider the potential for increased immunosuppressive risks from both agents.(1) The most common infections reported by sarilumab treated patients in the clinical trial periods included pneumonia and cellulitis. Serious bacterial, mycobacterial, fungal, and viral infections were observed in patients receiving sarilumab. Cases of tuberculosis, candidiasis, and pneumocystis with sarilumab have been reported.(1)

Immunosuppressives; Immunomodulators/Tocilizumab

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Tocilizumab, immunosuppressives, and immunomodulators all suppress the immune system.(1)

CLINICAL EFFECTS: Concurrent use of tocilizumab with immunosuppressive or immunomodulating agents may result in an increased risk for serious infections.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of tocilizumab recommends caution because the concurrent use of tocilizumab with immunosuppressive agents may increase the risk of infection. If concurrent therapy is warranted, consider the risk of additive immune suppression and monitor based on prescribing information for both agents.(1)

DISCUSSION: Tocilizumab was studied as monotherapy and in combination with methotrexate, non-biologic DMARDs or corticosteroids, depending on the indication. Tocilizumab has not been studied with biological DMARDs and concurrent use should be avoided. If concurrent therapy is warranted, consider the potential for increased immunosuppressive risks from both agents.(1) The most common infections reported by tocilizumab treated patients in the clinical trial periods included pneumonia, urinary tract infection, cellulitis, herpes zoster, gastroenteritis, diverticulitis, sepsis and bacterial arthritis. Serious bacterial, mycobacterial, fungal, and viral infections were observed in patients receiving tocilizumab. Cases of tuberculosis, cryptococcus, aspergillosis, candidiasis, and pneumocystosis have been reported.(1)

Immunosuppressives; Immunomodulators/Ublituximab

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Ublituximab, immunosuppressives, and immunomodulators all suppress the immune system.(1)

CLINICAL EFFECTS: Concurrent use of ublituximab with immunosuppressive or immunomodulating agents may result in an increased risk for serious infections.(1)

PREDISPOSING FACTORS: Incomplete washout of previously prescribed immunosuppressive or immune-modulating medications.

PATIENT MANAGEMENT: The US manufacturer of ublituximab recommends caution because the concurrent use of ublituximab with immunomodulating or immunosuppressive agents, including immunosuppressant doses of corticosteroids, may increase the risk of infection.(1) If concurrent therapy is warranted, consider the risk of additive immune suppression and monitor based on prescribing information for both agents. When switching from agents with immune effects, the half-life and mechanism of action of these drugs must be taken into consideration in order to prevent additive immunosuppressive effects.(1)

DISCUSSION: The most common infections reported by ublituximab-treated patients in the clinical trial periods included upper respiratory tract infections and urinary tract infections. Serious, including life-threatening or fatal, bacterial and viral infections were observed in patients receiving ublituximab.(1) Serious and/or fatal bacterial, fungal, and new or reactivated viral infections have been associated with other anti-CD20 B-cell depleting therapies. There were no cases of progressive multifocal leukoencephalopathy (PML) reported during the clinical trials; however, there have been reports of PML during or following completion of other anti-CD20 B-cell depleting therapies.(1)

Immunosuppressives; Immunomodulators/Ustekinumab

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Ustekinumab, immunosuppressives, and immunomodulators all suppress the immune system.(1)

CLINICAL EFFECTS: Concurrent use of ustekinumab with immunosuppressive or immunomodulating agents may result in an increased risk for serious infections.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of ustekinumab recommends caution because the concurrent use of ustekinumab with immunosuppressive agents may increase the risk of infection. If concurrent therapy is warranted, consider the risk of additive immune suppression and monitor based on prescribing information for both agents.(1)

DISCUSSION: Ustekinumab has not been studied in combination with other immunosuppressants in psoriasis studies. In psoriatic arthritis studies, concomitant methotrexate use did not appear to influence the safety or efficacy of ustekinumab. In Crohn's disease and ulcerative colitis studies, concomitant use of immunosuppressants or corticosteroids did not appear to influence the safety or efficacy of ustekinumab. If concurrent therapy is warranted, consider the potential for increased immunosuppressive risks from both agents.(1) The most common infections reported by ustekinumab treated patients in the clinical trial periods included nasopharyngitis(8%) and upper respiratory tract infection(5%). Serious bacterial, mycobacterial, fungal, and viral infections were observed in patients receiving ustekinumab. Cases of interstitial pneumonia, eosinophilic pneumonia, and cryptogenic organizing pneumonia resulting in respiratory failure or prolonged hospitalization have been reported in patients receiving ustekinumab.(1)

Oatp1b1-3 Inhibitors/Atogepant

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Atogepant is a substrate of OATP1B1 and 1B3. Inhibitors of these transporters may increase the GI absorption and/or decrease the hepatic uptake of atogepant.(1)

CLINICAL EFFECTS: Concurrent use of OATP1B1 or 1B3 inhibitors may result in elevated levels of and side effects from atogepant, including nausea, constipation and fatigue.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of atogepant states that, when used concurrently with an OATP inhibitor for prevention of episodic migraine, the atogepant dose should be limited to 10 mg or 30 mg once daily. When used concurrently with an OATP inhibitor for prevention of chronic migraines, the atogepant dose should be limited to 30 mg once daily.(1)

DISCUSSION: In a clinical trial of healthy subjects, single-dose rifampin, an OATP inhibitor, increased the atogepant area-under-curve (AUC) and maximum concentration (Cmax) by 2.85-fold and 2.23-fold, respectively.(1) OATP1B1 and 1B3 inhibitors include: atazanavir, belumosudil, cyclosporine, darunavir, eltrombopag, erythromycin, gemfibrozil, glecaprevir-pibrentasvir, ledipasvir, leflunomide, leniolisib, letermovir, paritaprevir, resmetirom, ritonavir, roxadustat, simeprevir, sofosbuvir, teriflunomide, vadadustat, velpatasvir, and voclosporin.(1,2)

Oatp1b1-3 Inhibitors/Momelotinib

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: OATP1B1 and 1B3 inhibitors may decrease the hepatic uptake of momelotinib.(1)

CLINICAL EFFECTS: Concurrent use of OATP1B1 and 1B3 inhibitors may result in elevated levels of and side effects from momelotinib, including myelosuppression and hepatotoxicity.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Concurrent use of momelotinib with OATP1B1 and 1B3 inhibitors should be approached with caution. Monitor patients closely for adverse reactions and consider dose modifications per momelotinib prescribing recommendations.(1)

DISCUSSION: Concurrent administration of a single dose rifampin, an OATP1B1/1B3 inhibitor, increased the maximum concentration (Cmax) and area-under-curve (AUC) of a single dose of momelotinib by 40% and 57%, respectively. The M21 metabolite Cmax increased 6% and AUC increased 12%.(1) OATP1B1 inhibitors include: atazanavir, belumosudil, boceprevir, cobicistat, cyclosporine, darolutamide, darunavir, eltrombopag, enasidenib, encorafenib, erythromycin, fostemsavir, gemfibrozil, glecaprevir-pibrentasvir, ledipasvir, letermovir, lopinavir, nirmatrelvir, paritaprevir, resmetirom, rifampin, roxadustat, saquinavir, simeprevir, telaprevir, tipranavir, vadadustat, velpatasvir, and voclosporin.(1,2)

P-Glycoprotein (P-GP) Inhibitors/Afatinib

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Inhibitors of P-glycoprotein (P-gp) may increase the absorption of afatinib.(1)

CLINICAL EFFECTS: The concurrent administration of afatinib with an inhibitor of P-glycoprotein may result in elevated levels of afatinib and signs of toxicity. These signs may include but are not limited to worsening diarrhea, stomatitis, skin rash/exfoliation/bullae or paronychia.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of afatinib states the afatinib dose should be reduced by 10 mg if the addition of a P-glycoprotein inhibitor is not tolerated.(1) If afatinib dose was reduced due to addition of a P-gp inhibitor, resume the previous dose after the P-gp inhibitor is discontinued.(1) The manufacturer of vimseltinib states concurrent use with P-gp substrates should be avoided. If concurrent use cannot be avoided, take vimseltinib at least 4 hours prior to afatinib.(2) The manufacturer of daraxonrasib states P-gp substrates should be administered at least 4 hours apart from daraxonrasib.(4)

DISCUSSION: A drug interaction study evaluated the effects of ritonavir 200 mg twice daily on afatinib exposure. Administration of ritonavir 1 hour before afatinib administration increased systemic exposure by 48%. Afatinib exposure was not changed when ritonavir was administered simultaneously with or 6 hours after afatinib dose.(1) P-glycoprotein inhibitors linked to this monograph are: amiodarone, asunaprevir, aumolertinib, azithromycin, belumosudil, capmatinib, carvedilol, cimetidine, clarithromycin, cobicistat, cyclosporine, danicopan, daraxonrasib, daridorexant, deutivacaftor, diosmin, dronedarone, erythromycin, flibanserin, fostamatinib, ginseng, glecaprevir/pibrentasvir, hydroquinidine, imlunestrant, isavuconazonium, itraconazole, ivacaftor, josamycin, ketoconazole, lapatinib, ledipasvir, lonafarnib, mavorixafor, neratinib, osimertinib, posaconazole, propafenone, quinidine, ranolazine, ritonavir, saquinavir, selpercatinib, sofosbuvir/velpatasvir/voxilaprevir, sotorasib, telaprevir, tepotinib, tucatinib, valbenazine, vemurafenib, vepdegestrant, verapamil, vimseltinib and voclosporin.(1-3)

P-Glycoprotein (P-GP) Inhibitors/Etoposide

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: P-glycoprotein (P-gp) inhibition may increase etoposide cellular concentration, decrease biliary or renal elimination, and increase systemic absorption of oral etoposide.(1-4)

CLINICAL EFFECTS: Increased cellular or systemic levels of etoposide may result in etoposide toxicity.

PREDISPOSING FACTORS: The interaction magnitude may be greater in patients receiving oral etoposide, or with impaired renal or hepatic function.

PATIENT MANAGEMENT: Anticipate and monitor for increased hematologic and gastrointestinal toxicities. Adjust or hold etoposide dose when needed. In patients receiving high-dose cyclosporine therapy, etoposide dosages should be reduced by 50%.(1) Monitor for signs of etoposide toxicity. Dosages may need further adjustment. The manufacturer of vimseltinib states concurrent use with P-gp substrates should be avoided. If concurrent use cannot be avoided, take vimseltinib at least 4 hours prior to etoposide.(5) The manufacturer of daraxonrasib states that P-gp substrates should be taken 4 hours apart from daraxonrasib.(6)

DISCUSSION: In a study in 16 patients, the administration of etoposide plus cyclosporine increased etoposide area-under-curve (AUC) by 59% and half-life by 73%. Etoposide renal clearance was decreased by 38% and nonrenal clearance was decreased by 52%. White blood cell count nadir was significantly lower during concurrent therapy with cyclosporine and etoposide (1200 mm3) when compared to etoposide alone (2500 mm3). There was also a trend for higher dosages of cyclosporine to exert increased effects on etoposide, although this difference did not reach statistical significance.(1) P-gp inhibitors linked to this monograph include: asciminib, asunaprevir, aumolertinib, azithromycin, belumosudil, capmatinib, cimetidine, clarithromycin, cyclosporine, daraxonrasib, daridorexant, danicopan, deutivacaftor, diosmin, flibanserin, fostamatinib, glecaprevir/pibrentasvir, imlunestrant, itraconazole, ivacaftor, josamycin, ketoconazole, lonafarnib, mavorixafor, neratinib, osimertinib, pirtobrutinib, posaconazole, propafenone, quinidine, selpercatinib, sofosbuvir/velpatasvir/voxilaprevir, sotorasib, tepotinib, tucatinib, valbenazine, vemurafenib, vepdegestrant, verapamil, vimseltinib, and voclosporin.

P-Glycoprotein (P-GP) Inhibitors/Mavorixafor

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Mavorixafor is a substrate of the P-glycoprotein (P-gp) transporter. P-gp inhibitors may significantly increase the absorption of mavorixafor.(1)

CLINICAL EFFECTS: Concurrent administration of mavorixafor with an inhibitor of P-glycoprotein may result in elevated levels of and effects from mavorixafor, including potentially life-threatening cardiac arrhythmias, torsades de pointes, and sudden death.(1)

PREDISPOSING FACTORS: The risk of QT prolongation or torsades de pointes may be increased in patients with cardiovascular disease (e.g. heart failure, myocardial infarction, history of torsades de pointes, congenital long QT syndrome), hypokalemia, hypomagnesemia, hypocalcemia, bradycardia, female gender, or advanced age.(2) Concurrent use of more than one drug known to cause QT prolongation or higher systemic concentrations of either QT prolonging drug are additional risk factors for torsades de pointes. Factors which may increase systemic drug concentrations include rapid infusion of an intravenous dose or impaired metabolism or elimination of the drug (e.g. coadministration with an agent which inhibits its metabolism or elimination, and/or renal/hepatic dysfunction).(2)

PATIENT MANAGEMENT: When used concomitantly with P-gp inhibitors, monitor more frequently for mavorixafor adverse effects and reduce the dose in 100 mg increments, if necessary, but not to a dose less than 200 mg.(1) The manufacturer of vimseltinib states concurrent use with P-gp substrates should be avoided. If concurrent use cannot be avoided, take vimseltinib at least 4 hours prior to mavorixafor.(4) When concurrent therapy is warranted, consider obtaining serum calcium, magnesium, and potassium levels and monitoring EKG at baseline and regular intervals. Correct any electrolyte abnormalities. Instruct patients to report any irregular heartbeat, dizziness, or fainting.

DISCUSSION: In a study with healthy subjects, itraconazole 200 mg daily (a strong CYP3A4 and P-gp inhibitor) increased the exposure to single-dose mavorixafor 200 mg similar to that from single-dose mavorixafor 400 mg alone. This suggests that itraconazole increased mavorixafor exposure by about 2-fold.(1) A study in healthy volunteers found that ritonavir 100 mg twice daily (a strong CYP3A4 inhibitor and P-gp inhibitor) increased the area-under-curve (AUC) and maximum concentration (Cmax) of single-dose mavorixafor 200 mg by 60% and 39%, respectively.(1) P-glycoprotein inhibitors linked to this monograph include: abrocitinib, Asian ginseng, asunaprevir, capmatinib, carvedilol, cyclosporine, danicopan, daridorexant, deutivacaftor, diosmin, elagolix, flibanserin, fostamatinib, ginkgo biloba, glecaprevir/pibrentasvir, ivacaftor, milk thistle, neratinib, pirtobrutinib, quercetin, rolapitant, sofosbuvir/velpatasvir/voxilaprevir, tepotinib, velpatasvir, vilazodone, vimseltinib, and voclosporin.(1,4-6)

P-Gp Inhibitors/Rimegepant

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Rimegepant is a calcitonin gene-related peptide receptor antagonist. Rimegepant is a substrate of the P-glycoprotein (P-gp) transporter. P-gp inhibitors may significantly increase the absorption of rimegepant.(1)

CLINICAL EFFECTS: The concurrent administration of rimegepant with an inhibitor of P-glycoprotein may result in elevated levels of rimegepant.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of rimegepant recommends avoiding a second dose of rimegepant within 48 hours of a first dose when used concomitantly with P-gp inhibitors.(1) For patients on daraxonrasib, the manufacturer of daraxonrasib states that it should be taken at least 4 hours apart from P-gp substrates.(2)

DISCUSSION: Rimegepant is a substrate of P-gp. Use of P-gp inhibitors may increase the exposure of rimegepant. In a study, cyclosporine (a potent P-gp and BCRP inhibitor) increased rimegepant area-under curve (AUC) and maximum concentration (Cmax) by 1.6- and 1.4-fold, respectively. Quinidine (a potent P-gp inhibitor) similarly increased rimegepant AUC and Cmax by 1.6- and 1.7-fold, respectively. Therefore, the effect of these drug interactions were concluded to be due entirely to P-gp and not BCRP.(1) P-glycoprotein inhibitors linked to this monograph include: amiodarone, aumolertinib, azithromycin, belumosudil, capmatinib, carvedilol, cyclosporine, danicopan, daraxonrasib, daridorexant, diosmin, flibanserin, fostamatinib, glecaprevir/pibrentasvir, imlunestrant, lapatinib, mavorixafor, osimertinib, pirtobrutinib, propafenone, quinidine, ranolazine, selpercatinib, sofosbuvir/velpatasvir/voxilaprevir, tepotinib, vemurafenib, vepdegestrant, vimseltinib, and verapamil.(1-4)

Selected Cyp3a4 Inhibitors/Tolterodine (<=1 MG OR <=2 MG ER)

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Cyclosporine, erythromycin, miconazole, and vinblastine may inhibit the metabolism of tolterodine by CYP3A4.(1,2)

CLINICAL EFFECTS: The concurrent administration of tolterodine with cyclosporine, erythromycin, miconazole, or vinblastine may result in elevated levels of tolterodine and signs of toxicity.(1,2)

PREDISPOSING FACTORS: Patients who are CYP2D6 poor metabolizers may be at increased risk.(1,2) The risk of QT prolongation or torsades de pointes may be increased in patients with cardiovascular disease (e.g. heart failure, myocardial infarction, history of torsades de pointes, congenital long QT syndrome), hypokalemia, hypomagnesemia, hypocalcemia, bradycardia, female gender, or advanced age.(3) Concurrent use of more than one drug known to cause QT prolongation or higher systemic concentrations of either QT prolonging drug are additional risk factors for torsades de pointes. Factors which may increase systemic drug concentrations include rapid infusion of an intravenous dose or impaired metabolism or elimination of the drug (e.g. coadministration with an agent which inhibits its metabolism or elimination, genetic impairment in drug metabolism or elimination, and/or renal/hepatic dysfunction).(3) The risk of anticholinergic toxicities including cognitive decline, delirium, falls and fractures is increased in geriatric patients using more than one medicine with anticholinergic properties.(4)

PATIENT MANAGEMENT: The manufacturer of tolterodine recommends that a maximum tolterodine dosage of 1 mg twice daily of the non extended release dosage form(1) or 2 mg once daily of the extended release dosage form(2) be used in patients receiving concurrent therapy with cyclosporine, erythromycin, miconazole, or vinblastine. If concurrent therapy is warranted, consider obtaining serum calcium, magnesium, and potassium levels and monitoring ECG at baseline and at regular intervals. Correct any electrolyte abnormalities. Instruct patients to report any irregular heartbeat, dizziness, or fainting.

DISCUSSION: In a study in eight subjects who were deficient in CYP2D6, the concurrent administration of tolterodine (2 mg) with ketoconazole (200 mg once daily for four days), another inhibitor of CYP3A4, resulted in a 60% decrease in tolterodine clearance.(5) Tolterodine AUC and Cmax increased 2.5-fold and 2-fold, respectively.(2) In a study of the effect of tolterodine immediate release tablets, the effect on the QT interval appeared greater for 8 mg/day (two times the therapeutic dose) compared to 4 mg/day. Tolterodine 2 mg BID and tolterodine 4 mg BID increased the QTcF by 5.01 msec (0.28-9.74 msec) and 11.84 msec (7.11-16.58 msec), respectively. The change in QT interval was more pronounced in CYP2D6 poor metabolizers (PM) than extensive metabolizers (EMs).(1,2)

Selected Immunosuppressants/Maribavir

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: The metabolism of cyclosporine, everolimus, sirolimus, tacrolimus and temsirolimus by CYP3A4 may be inhibited by maribavir.

CLINICAL EFFECTS: Concurrent administration of maribavir may result in elevated levels of and toxicity from cyclosporine, everolimus, sirolimus, tacrolimus or temsirolimus.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Cyclosporine, everolimus, sirolimus, tacrolimus or temsirolimus levels and renal function should be monitored frequently during therapy with maribavir. Monitor immunosuppressant levels closely during initiation and after discontinuation of maribavir. The dosage of cyclosporine, everolimus, sirolimus, tacrolimus or temsirolimus may need to be adjusted.

DISCUSSION: In a study in 20 patients, maribavir increased the area-under-curve (AUC), concentration maximum (Cmax), and Ctau of tacrolimus by 51%, 38%, and 57%, respectively. In a multiple-dose study, concomitant administration of ketoconazole with sirolimus oral solution increased the sirolimus Cmax, time to Cmax (Tmax), and AUC by 4.3-fold, 38%, and 10.9-fold, respectively. Single-dose sirolimus did not affect steady-state 12-hour plasma ketoconazole concentrations. In a study in 6 patients, ketoconazole was successfully used to augment sirolimus levels. Patients were able to receive one-eight to one-fourth (0.25 - 0.50 mg daily) of the usual sirolimus dose while taking 100 to 200 mg of ketoconazole daily. Concurrent administration of ketoconazole had no effects on temsirolimus AUC or Cmax; however, sirolimus AUC and Cmax increased 3.1-fold and 2.2-fold, respectively. Dosage adjustment of temsirolimus to 12.5 mg/week in the presence of strong CYP3A4 inhibitors is expected to adjust levels to the range observed without inhibitors; however, there are no data available with this dose adjustment.

Selected Nephrotoxic Agents/Tenofovir

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Tenofovir and other nephrotoxic agents may result in additive or synergistic effects on renal function and increase nephrotoxicity risk.(1)

CLINICAL EFFECTS: Concurrent use of tenofovir and other nephrotoxic agents may result in renal toxicity and acute renal failure.(1) Reports of acute renal failure and Fanconi syndrome have been reported with tenofovir use.(2,3) However, this has been reported in 3 case reports and the renal failure may have been complicated by other pre-existing conditions.(2)

PREDISPOSING FACTORS: Pre-existing renal dysfunction, long duration of use, low body weight, concomitant use of drugs that may increase tenofovir levels may increase the risk of nephrotoxicity.(1)

PATIENT MANAGEMENT: The US prescribing information for tenofovir recommends avoiding concurrent or recent use of a nephrotoxic agent.(3) Evaluate renal function prior to initiation of concurrent therapy and continue renal function monitoring during therapy. Dose adjustments may be required for impaired renal function. Tenofovir should be avoided with high-dose or multiple NSAIDs. Alternatives to NSAIDs should be considered in patients at risk for renal dysfunction.(3) Patients receiving concurrent NSAIDs with tenofovir should be monitored for possible renal toxicity.(1,2) The dosing interval should be adjusted in patients with a baseline creatinine clearance of less than 50 ml/min.(1-3)

DISCUSSION: From March 18, 2003 to December 1, 2005, Health Canada received 10 reports of nephrotoxic reactions with tenofovir. Three of these occurred following the addition of a NSAID to tenofovir therapy. In the first report, a patient maintained on tenofovir for 29 months developed acute renal failure and acute tubular necrosis requiring dialysis 5 days after beginning indomethacin (100 mg rectally twice daily). In the second report, a patient maintained on tenofovir for 7 months developed acute renal failure and acute tubular necrosis after taking 90 tablets of naproxen (375 mg) over 2 months. The patient died. In the third report, a patient maintained on tenofovir for over a year developed acute renal failure and nephrotic syndrome after 2 months of valdecoxib (20 mg daily) therapy. Symptoms subsided following discontinuation of valdecoxib.(1)

Selected P-Glycoprotein (P-GP) Inhibitors/Betrixaban

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Betrixaban is a substrate for the P-glycoprotein (P-gp) system. Inhibition of intestinal P-gp leads to increased absorption of betrixaban.(1)

CLINICAL EFFECTS: The concurrent use betrixaban with P-gp inhibitors may lead to elevated plasma levels of betrixaban, increasing the risk for bleeding.

PREDISPOSING FACTORS: Factors associated with an increased risk for bleeding include renal impairment, concomitant use of P-gp inhibitors, coexisting conditions (e.g. recent trauma) or use of drugs (e.g. NSAIDs) associated with bleeding risk, and patient weight < 50 kg.(1)

PATIENT MANAGEMENT: Assess renal function and evaluate patient for other pre-existing risk factors for bleeding prior to initiating concurrent therapy. The concurrent use of betrixaban and P-gp inhibitors should be avoided in patients with severe renal impairment (CrCl less than 30 ml/min).(1) The recommended dose for patients receiving or starting concomitant P-gp inhibitors is an initial single dose of 80 mg followed by 40 mg once daily. The recommended duration of treatment is 35 to 42 days.(1) Note that if betrixaban is used with the combination of darunavir and cobicistat, dose adjustment of betrixaban is not necessary.(2) The manufacturer of vimseltinib states concurrent use with P-gp substrates should be avoided. If concurrent use cannot be avoided, take vimseltinib at least 4 hours prior to betrixaban.(3) Careful monitoring for signs and symptoms of bleeding is warranted during concurrent therapy. Consider regular monitoring of hemoglobin, platelet levels, and/or activated partial thromboplastin time (aPTT) or ecarin clotting time (ECT). Instruct patients to report any signs and symptoms of bleeding, such as bleeding from the eyes, gums or nose; unusual bruising; dark stools; red or dark brown urine; and/or abdominal pain or swelling.(1) The anticoagulant effect of betrixaban is expected to persist for at least 72 hours after the last dose. The manufacturer of daraxonrasib states P-gp substrates should be administered at least 4 hours apart from daraxonrasib.(8)

DISCUSSION: In the APEX randomized, double-blind study the incidence of major or clinically relevant non-major bleeds (CRNM) in the betrixaban 40mg and 80 mg group was higher in patients taking concomitant P-gp inhibitors (2.8% vs. 4.1% vs. 4.7%).(4) In a study in 12 subjects, concomitant administration of a single dose of betrixaban (40 mg) following a 5-day regimen of ketoconazole (200 mg twice daily) resulted in an increase in betrixaban's maximum concentration (Cmax) and area-under-the-curve (AUC) of 2.3-fold and 2.3-fold, respectively.(5) An open-label study looking at concomitant administration of a single dose of betrixaban with verapamil in 18 subjects found an increase in betrixaban's Cmax and AUC of approximately 4.7-fold and 3-fold, respectively.(5) In a study, concomitant administration of betrixaban (80 mg) with amiodarone resulted in an increase in betrixaban's Cmax by 143%.(5) A summary of pharmacokinetic interactions with betrixaban and amiodarone, diltiazem, or verapamil concluded that if concurrent use is warranted, the betrixaban dose should be reduced to 80 mg once then 40 mg daily. Use should be avoided if CrCl is less than 30 ml/min.(6) P-gp inhibitors include asunaprevir, aumolertinib, azithromycin, belumosudil, capmatinib, carvedilol, cimetidine, clarithromycin, cobicistat, conivaptan, cyclosporine, daclatasvir, danicopan, daraxonrasib, daridorexant, diltiazem, diosmin, dronedarone, erythromycin, flibanserin, fostamatinib, ginseng, glecaprevir, hydroquinidine, imlunestrant, indinavir, itraconazole, ivacaftor, josamycin, lapatinib, ledipasvir, lonafarnib, lopinavir, mavorixafor, neratinib, osimertinib, pibrentasvir, pirtobrutinib, posaconazole, propafenone, quinidine, ranolazine, ritonavir, selpercatinib, sofosbuvir/velpatasvir/voxilaprevir, sotorasib, telaprevir, telithromycin, tepotinib, tezacaftor, tucatinib, valbenazine, velpatasvir, vemurafenib, vepdegestrant, vimseltinib, voclosporin and voxilaprevir.(1,4-7)

Selected P-Gp And Weak Cyp3a4 Inhibitors/Rivaroxaban

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Amiodarone, azithromycin, brodalumab, chloramphenicol, cimetidine, cyclosporine, felodipine, fluvoxamine, fostamatinib, glecaprevir/pibrentasvir, hydroquinidine, ivacaftor, nilotinib, piperine, pirtobrutinib, quinidine, ranolazine, simeprevir, ticagrelor and tolvaptan may inhibit the metabolism of rivaroxaban by CYP3A4 and by P-glycoprotein.(1,2)

CLINICAL EFFECTS: Concurrent use of an agent that is both an inhibitor of P-gp and a weak inhibitor of CYP3A4 may result in elevated levels of and clinical effects of rivaroxaban, including an increased risk of bleeding, in patients with decreased renal function.(1,2)

PREDISPOSING FACTORS: Patients with decreased renal function (CrCL of 15 ml/min to 80 ml/min) may be predisposed to this interaction.(1) The risk for bleeding episodes may be greater in patients with disease-associated factors (e.g. thrombocytopenia). Drug associated risk factors include concurrent use of multiple drugs which inhibit anticoagulant/antiplatelet metabolism and/or have an inherent risk for bleeding (e.g. NSAIDs).

PATIENT MANAGEMENT: The US manufacturer states no precautions are necessary with the concurrent use of these agents and rivaroxaban in patients with normal renal function.(1) It would be prudent to closely monitor concurrent use in patients with reduced renal function (CrCL of 15 ml/min to 80 ml/min). If concurrent therapy is warranted, monitor patients receiving concurrent therapy for signs of blood loss, including decreased hemoglobin, hematocrit, fecal occult blood, and/or decreased blood pressure and promptly evaluate patients with any symptoms. When applicable, perform agent-specific laboratory test (e.g. INR, aPTT) to monitor efficacy and safety of anticoagulation. Discontinue anticoagulation in patients with active pathologic bleeding. Instruct patients to report any signs and symptoms of bleeding, such as unusual bleeding from the gums or nose; unusual bruising; red or black, tarry stools; red, pink or dark brown urine; acute abdominal or joint pain and/or swelling.

DISCUSSION: Clarithromycin (500 mg twice daily) increased the area-under-curve (AUC) and maximum concentration (Cmax) of a single dose of rivaroxaban by 50% and 40%, respectively.(1,2) Erythromycin (500 mg three times daily) increased the AUC and Cmax of a single dose of rivaroxaban by 30% and 30%, respectively.(1-3) In patients with mild renal impairment (CrCl of 50 ml/min to 79 ml/min) who were receiving erythromycin, rivaroxaban levels were increased 76% when compared to administration of rivaroxaban in patients with normal renal function receiving rivaroxaban alone. In patients with moderate renal impairment (CrCl of 30 ml/min to 49 ml/min) who were receiving erythromycin, rivaroxaban levels were increased 99% when compared to administration of rivaroxaban in patients with normal renal function receiving rivaroxaban alone.(1) Fluconazole increased the AUC and Cmax of a single dose of rivaroxaban by 40%% and 30%, respectively.(1) These changes are not expected to be clinically significant in patients with normal renal function.(1,2) In a case report, an 88-year-old woman with renal impairment on rivaroxaban presented with an elevated INR of 2.5 and a rivaroxaban peak plasma concentration above the upper limit of detection at >800 mcg/L (therapeutic range 58-211 mcg/L). Nothing in her medical history suggested a reason for supratherapeutic rivaroxaban levels except for a 7-week amiodarone regimen that was discontinued 3 weeks prior. This suggests the potential for amiodarone to persist in the body weeks after its use and precipitate drug-drug interactions.(4) A retrospective cohort study examined 24,943 patients aged 66 years and older with concurrent therapy of an anticoagulant, either rivaroxaban (40.0%), apixaban (31.9%), or dabigatran (28.1%), with either azithromycin or clarithromycin. The primary outcome of hospital admission with major hemorrhage within 30 days on concurrent therapy was higher in patients on clarithromycin (0.77%) compared to azithromycin (0.43%) with an adjusted hazard ratio of 1.71 (95% CI, 1.20-2.45). In a self-controlled case series, 744 major hemorrhage events were identified among 647 unique individuals taking anticoagulants who were exposed to clarithromycin. The rate of events that occurred during clarithromycin use had a significant rate ratio of 1.44 (95% CI, 1.08-1.92).(5) A propensity matched cohort evaluated the concurrent use of combined P-gp and moderate CYP3A4 inhibitors with apixaban or rivaroxaban. Combined inhibitors included amiodarone, diltiazem, erythromycin, dronedarone, and verapamil. Bleeding occurred in 26.4% of patients in the inhibitor group compared to 18.4% in the control group (hazard ratio 1.8; 95% CI 1.19-2.73; p=0.006). Although not statistically significant, patients in the inhibitor group also had a higher rate of major bleeding (15% vs 10.3%) and minor bleeding (8.9% vs 5.2%), respectively.(6) A summary of pharmacokinetic interactions with rivaroxaban and amiodarone concluded that concurrent use should be avoided if CrCl < 80 ml/min.(7) A prospective cohort study of 174 patients evaluated the concurrent use of rivaroxaban and amiodarone. The combination of rivaroxaban and amiodarone was associated with a higher incidence of bleeding events (p=0.041; HR=2.83, 95% CI 1.05-7.66) and clinically relevant non-major bleeding (p=0.021; HR=3.65, 95% CI 1.21-10.94). Concurrent use of amiodarone and rivaroxaban in non-valvular atrial fibrillation patients was an independent risk factor for increased risk of bleeding (p=0.044; OR 2.871, 95% CI 1.028-8.023).(8) P-gp and weak CYP3A4 inhibitors linked to this monograph are: amiodarone, azithromycin, belumosudil, brodalumab, chloramphenicol, cimetidine, cyclosporine, daridorexant, diosmin, flibanserin, fostamatinib, glecaprevir/pibrentasvir, hydroquinidine, istradefylline, ivacaftor, mavorixafor, nilotinib, piperine, pirtobrutinib, quinidine, ranolazine, selpercatinib, simeprevir, tolvaptan, and vepdegestrant.(9,10)

Selected P-Gp Inhibitors/Edoxaban (<= 30 MG)

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Edoxaban is a substrate for P-glycoprotein (P-gp). Inhibitors of P-gp may increase intestinal absorption and decrease renal tubular elimination of edoxaban.(1,2)

CLINICAL EFFECTS: Concurrent use with selected P-gp inhibitors may result in higher systemic concentrations of edoxaban which may increase the risk for bleeding.(1-5) P-gp inhibitors linked to this interaction are: cyclosporine, dronedarone, erythromycin, and ketoconazole.

PREDISPOSING FACTORS: Bleeding risk may be increased in patients with creatinine clearance 15mL - 50 mL per minute(1) or weight less than or equal to 60 kg.(2) Use of multiple agents which increase edoxaban exposure or affect hemostasis would be expected to increase the risk for bleeding. The risk for bleeding episodes may be greater in patients with disease-associated factors (thrombocytopenia). Drug associated risk factors include concurrent use of multiple drugs which inhibit anticoagulant/antiplatelet metabolism and/or have an inherent risk for bleeding (e.g. NSAIDs).

PATIENT MANAGEMENT: Management recommendations vary depending upon the approving regulatory agency (FDA or European Medicines Agency, EMA). US FDA recommendations are based upon the edoxaban indication: - For treatment of deep vein thrombosis (DVT) or pulmonary embolism (PE), the edoxaban dose should be reduced to 30 mg daily when used concomitantly with erythromycin or oral ketoconazole.(3) - For prevention of stroke or embolic events due to nonvalvular atrial fibrillation, no edoxaban dose adjustments are recommended during concomitant therapy with P-glycoprotein inhibitors.(1,3) - Concurrent use of cyclosporine was not allowed in edoxaban clinical trials (atrial fibrillation or DVT/PE). US prescribing information does not provide specific management information for concurrent use of cyclosporine with edoxaban.(3) EMA dosage adjustments are the same, regardless of indication: - Reduce edoxaban dose to 30 mg daily in patients receiving concomitant treatment with cyclosporine, dronedarone, erythromycin or oral ketoconazole.(4) Monitor patients receiving concurrent therapy for signs of blood loss, including decreased hemoglobin and/or hematocrit, fecal occult blood, and/or decreased blood pressure and promptly evaluate patients with any symptoms. When applicable, perform agent-specific laboratory test (e.g. anti Factor Xa inhibition) to monitor efficacy and safety of anticoagulation. Discontinue anticoagulation in patients with active pathologic bleeding. Instruct patients to report any signs and symptoms of bleeding, such as unusual bleeding from the gums or nose; unusual bruising; red or black, tarry stools; red, pink or dark brown urine; acute abdominal or joint pain and/or swelling. Discontinue edoxaban in patients with active bleeding.

DISCUSSION: Edoxaban in vivo interaction studies have been performed for P-gp inhibitors linked to this monograph: In an interaction study, the effect of single oral dose of cyclosporine 500 mg on a single oral dose of edoxaban 60 mg was evaluated in healthy subjects. Total and peak systemic exposure to edoxaban increased 1.73-fold and 1.74-fold, respectively. Total and peak systemic exposure to the active M4 metabolite increased 6.87-fold and 8.71-fold respectively, likely due to cyclosporine inhibition of OATP1B1.(1) In the absence of OATP1B1 inhibition, M4 concentrations are generally less than or equal to 10% of edoxaban exposure,(1) but the approximately 7-fold increase in active metabolite exposure may result in clinically meaningful concentrations of M4. In an interaction study, the effect of repeat administration of dronedarone (400 mg bid) on a single oral dose of edoxaban 60 mg was evaluated in healthy subjects. Total and peak systemic exposure to edoxaban increased 1.84-fold and 1.45-fold, respectively. Plasma edoxaban concentrations 24 hours post dose (Ctrough) following coadministration edoxaban and dronedarone were 2.6-fold higher compared with administration of edoxaban alone.(1) In an interaction study, the effect of repeat administration of erythromycin (oral dose of 500 mg four times daily for 8 days) on a single oral dose of edoxaban 60 mg on on study day 7 was evaluated in healthy subjects. Total and peak systemic exposure to edoxaban increased 1.85-fold and 1.68-fold, respectively. Total and peak systemic exposure to the M4 metabolite increased 1.78-fold and 1.75-fold, respectively.(1) In an interaction study, the effect of repeat administration of ketoconazole (oral dose of 400 mg QD for 7 days) on a single oral dose of edoxaban (60 mg) was evaluated in healthy subjects. Total and peak systemic exposure to edoxaban increased 1.87-fold and 1.89-fold, respectively. Total and peak systemic exposure to the M4 metabolite increased 1.46-fold and 1.56-fold, respectively.(1) A summary of pharmacokinetic interactions with edoxaban and dronedarone concluded that if concurrent use is warranted, the edoxaban dose should be reduced by 50%.(6)

Weak Cyp3a4 Inhibitors/Lemborexant (<= 5 MG)

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Inhibitors of CYP3A4 may inhibit the metabolism of lemborexant.(1)

CLINICAL EFFECTS: Concurrent use of an inhibitor of CYP3A4 may result in increased levels of and effects from lemborexant, including somnolence, fatigue, CNS depressant effects, daytime impairment, headache, and nightmare or abnormal dreams.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The maximum recommended dose of lemborexant with concurrent use of a weak CYP3A4 inhibitors should not exceed 5 mg per dose.(1) For patients on avapritinib: this interaction applies only to gastrointestinal stromal tumor (GIST) patients on avapritinib 200 mg or 300 mg.(2)

DISCUSSION: Lemborexant is a CYP3A4 substrate. In a PKPB model, concurrent use of lemborexant with itraconazole increased area-under-curve (AUC) and concentration maximum (Cmax) by 3.75-fold and 1.5-fold, respectively. Concurrent use of lemborexant with fluconazole increased AUC and Cmax by 4.25-fold and 1.75-fold, respectively.(1) Weak inhibitors of CYP3A4 include: amiodarone, amlodipine, anamorelin, asciminib, avapritinib, azithromycin, Baikal skullcap, belumosudil, berberine, bicalutamide, blueberry, brodalumab, camizestrant, cannabidiol, capivasertib, chlorzoxazone, cilostazol, cimetidine, ciprofloxacin, clotrimazole, cranberry, cyclosporine, daclatasvir, daridorexant, delavirdine, dihydroberberine, diosmin, elinzanetant, everolimus, flibanserin, fosaprepitant, fostamatinib, gepotidacin, ginkgo, givinostat, glecaprevir/pibrentasvir, goldenseal, grazoprevir, isoniazid, istradefylline, ivacaftor, lacidipine, lapatinib, larotrectinib, lazertinib, leflunomide, levamlodipine, linagliptin, lomitapide, lurasidone, mavorixafor, olaparib, osilodrostat, palbociclib, pazopanib, peppermint oil, piperine, propiverine, propofol, ranitidine, ranolazine, resveratrol, roxithromycin, rucaparib, selpercatinib, simeprevir, sitaxsentan, skullcap, teriflunomide, ticagrelor, tolvaptan, trofinetide, vepdegestrant, viloxazine, vonoprazan, and ziftomenib.(1,3)

Weak Cyp3a4 Inhibitors/Mavacamten

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Weak CYP3A4 inhibitors may decrease the metabolism of mavacamten.(1)

CLINICAL EFFECTS: Concurrent use of weak CYP3A4 inhibitors may increase the plasma levels and the incidence and severity of adverse reactions of mavacamten.(1)

PREDISPOSING FACTORS: CYP2C19 poor metabolizers may experience an increased incidence or severity of adverse effects.(1)

PATIENT MANAGEMENT: The UK manufacturer of mavacamten states no dose adjustment is necessary when starting mavacamten in patients on weak CYP3A4 inhibitors or in intermediate, normal, rapid, or ultra-rapid CYP2C19 metabolizers already on mavacamten and starting a weak CYP3A4 inhibitor. In poor CYP2C19 metabolizers already on mavacamten and starting a weak CYP3A4 inhibitor, reduce mavacamten 5 mg to 2.5 mg or if on 2.5 mg pause treatment for 4 weeks. If CYP2C19 phenotype is unknown, consider a mavacamten starting dose of 2.5 mg daily.(1) For patients on avapritinib: this interaction applies only to gastrointestinal stromal tumor (GIST) patients on avapritinib 200 mg or 300 mg.(2)

DISCUSSION: In a PBPK model, concomitant use of mavacamten (15 mg daily) with cimetidine 400 mg twice daily, a weak CYP3A4 inhibitor, was predicted to increase mavacamten area-under-curve (AUC) by 6% and maximum concentration (Cmax) by 4% in poor CYP2C19 metabolizers and by 3% and 2%, respectively, in both intermediate and normal CYP2C19 metabolizers.(3) Weak CYP3A4 inhibitors include: amiodarone, amlodipine, anamorelin, asciminib, avapritinib, azithromycin, Baikal skullcap, belumosudil, berberine, bicalutamide, blueberry, brodalumab, chlorzoxazone, cilostazol, clotrimazole, cranberry, cyclosporine, delavirdine, dihydroberberine, diosmin, everolimus, flibanserin, fosaprepitant, fostamatinib, ginkgo, givinostat, glecaprevir/pibrentasvir, goldenseal, istradefylline, ivacaftor, lacidipine, lapatinib, leflunomide, levamlodipine, linagliptin, lomitapide, lurasidone, mavorixafor, pazopanib, peppermint oil, propiverine, propofol, ranitidine, resveratrol, roxithromycin, sitaxsentan, skullcap, teriflunomide, ticagrelor, tolvaptan, trofinetide, vepdegestrant, and viloxazine. (4,5)

Weak Cyp3a4 Inhibitors/Ubrogepant (<= 50 MG)

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Weak inhibitors of CYP3A4 may inhibit the metabolism of ubrogepant.(1)

CLINICAL EFFECTS: Concurrent use of ubrogepant with weak CYP3A4 inhibitors may result in an increase in exposure of ubrogepant.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer recommends a dosage adjustment of ubrogepant when used concomitantly with weak CYP3A4 inhibitors. Initial dose of ubrogepant should not exceed 50 mg when used concomitantly with weak inhibitors of CYP3A4. A second dose may be given within 24 hours but should not exceed 50 mg when used concurrently with weak CYP3A4 inhibitors.(1) For patients on avapritinib: this interaction applies only to gastrointestinal stromal tumor (GIST) patients on avapritinib 200 mg or 300 mg.(2)

DISCUSSION: Coadministration of ubrogepant with verapamil, a moderate CYP3A4 inhibitor, resulted in a 3.5-fold and 2.8-fold increase in area-under-curve (AUC) and concentration maximum (Cmax), respectively. No dedicated drug interaction study was conducted to assess concomitant use with weak CYP3A4 inhibitors. The conservative prediction of the maximal potential increase in ubrogepant exposure with weak CYP3A4 inhibitors is not expected to be more than 2-fold.(1) Weak inhibitors of CYP3A4 include: amiodarone, amlodipine, anamorelin, asciminib, avapritinib, azithromycin, Baikal skullcap, berberine, bicalutamide, blueberry, brodalumab, camizestrant, cannabidiol, capivasertib, chlorzoxazone, cilostazol, cimetidine, ciprofloxacin, clotrimazole, cranberry, cyclosporine, daclatasvir, delavirdine, deutivacaftor, dihydroberberine, diosmin, elinzanetant, everolimus, flibanserin, fosaprepitant, fostamatinib, gepotidacin, givinostat, glecaprevir/pibrentasvir, goldenseal, grazoprevir, isoniazid, istradefylline, ivacaftor, lacidipine, lapatinib, larotrectinib, lazertinib, leflunomide, levamlodipine, linagliptin, lomitapide, lurasidone, maribavir, mavorixafor, olaparib, osilodrostat, palbociclib, pazopanib, peppermint oil, piperine, pirtobrutinib, propiverine, propofol, ranitidine, ranolazine, resveratrol, roxithromycin, simeprevir, sitaxsentan, skullcap, teriflunomide, ticagrelor, tolvaptan, trofinetide, vepdegestrant, viloxazine, vonoprazan, and ziftomenib.(3,4)

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• Progressive multifocal leukoencephalopathy
• Severe uncontrolled hypertension

• BK polyomavirus reactivation nephropathy
• Disease of liver
• Hyperchloremic acidosis
• Hyperkalemia
• Hypomagnesemia
• Kidney disease with likely reduction in glomerular filtration rate (GFr)
• Kidney disease with reduction in glomerular filtration rate (GFr)
• Malignancy
• Malignant lymphoma

• Hypercholesterolemia
• Hypertension
• Hypertriglyceridemia
• Hyperuricemia
• Malabsorption states

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More Frequent

• Gingival hyperplasia
• Hypertension
• Nephrotoxicity

Less Frequent

• Bacterial sepsis
• Chest pain
• Dyspnea
• Fungal infection
• Hypomagnesemia
• Infection
• Jaundice
• Seizure disorder
• Skin rash

Rare or Very Rare

• Acute myocardial infarction
• Anaphylaxis
• Anemia
• Angioedema
• BK polyomavirus reactivation nephropathy
• Cholestasis
• Encephalopathy
• Hearing loss
• Hematuria
• Hemolytic uremic syndrome
• Hepatic failure
• Hepatitis
• Hyperglycemia
• Hyperkalemia
• Hyperuricemia
• Idiopathic intracranial hypertension
• Interstitial nephritis
• Malignant lymphoma
• Neoplasm
• Pancreatitis
• Parasitic infection
• Peptic ulcer
• Posterior reversible encephalopathy syndrome
• Progressive multifocal leukoencephalopathy
• Renal failure
• Thrombocytopenic disorder
• Thrombotic microangiography
• Thrombotic thrombocytopenic purpura
• Upper GI bleed
• Viral infection
• Visual changes

More Frequent

• Abdominal pain with cramps
• Dizziness
• Dyspepsia
• Edema
• Flu-like symptoms
• Headache disorder
• Hirsutism
• Pain
• Tremor
• Vomiting

Less Frequent

• Abdominal distension
• Acne vulgaris
• Cramps in legs
• Diarrhea
• Dyschromia
• Flatulence
• Gastritis
• Migraine
• Nausea
• Paresthesia
• Tinnitus

Rare or Very Rare

• Acute cognitive impairment
• Anorexia
• Arthralgia
• Basal cell carcinoma of skin
• Constipation
• Depression
• Dry skin
• Dysgeusia
• Dysphagia
• Fever
• Folliculitis
• General weakness
• Gynecomastia
• Hiccups
• Hyperkeratosis
• Hyperlipidemia
• Increased urinary frequency
• Lethargy
• Myalgia
• Night sweats
• Onychia sicca
• Pruritus of skin
• Sinusitis
• Squamous cell carcinoma of skin
• Stomatitis
• Symptoms of anxiety
• Weight loss

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No enhanced messaging available.

Although there are no adequate and well-controlled studies using cyclosporine in pregnant women, the drug has been shown to be embryotoxic and fetotoxic in rats and rabbits when administered orally at maternally toxic doses. Fetal toxicity was observed in these animals at doses 0.8-5.4 times (corrected for body surface area) the human maintenance dose of 6 mg/kg. Cyclosporine caused increased prenatal and postnatal mortality and reduced fetal weight with related skeletal retardation in these rats and rabbits. In women who received cyclosporine therapy throughout pregnancy, premature birth (gestational age of 28-36 weeks) and reduced neonatal weight occurred consistently. Most of the pregnancies also were complicated by growth retardation (which may be severe), fetal loss, preeclampsia, eclampsia, premature labor, abruptio placentae, oligohydramnios, Rh incompatibility, and fetoplacental dysfunction. Premature birth was the most frequent complication, while being small for gestational age and neonatal complications were less common. Malformations occurred in some neonates and in a few cases of fetal loss. A full-term neonate was born to a woman who underwent a renal transplant prior to conception and received 450 mg of cyclosporine alone daily throughout pregnancy, and other successful pregnancies have been reported in allograft recipients who received the drug daily during pregnancy. Abnormalities in renal function or blood pressure were not observed in a limited number of children 7 years of age or younger exposed to cyclosporine in utero.

Cyclosporine should be used during pregnancy only when the potential benefits justify the possible risks to the fetus. In patients with psoriasis, the risks and benefits of therapy with cyclosporine during pregnancy should be evaluated carefully, with discontinuance of therapy considered seriously because of possible disruption of the interaction between the mother and fetus.

Since cyclosporine is distributed into milk, nursing should be avoided in women receiving the drug.

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