Probenecid (probenecid)

When probenecid is used for the treatment of hyperuricemia associated with gout and gouty arthritis in patients with renal impairment, increased dosage of the drug may be required. The manufacturer states that probenecid may not be effective in patients with chronic renal insufficiency, especially if the glomerular filtration rate is 30 mL/minute or less. It has been suggested that the drug should be avoided in patients with moderate to severe renal impairment (creatinine clearance of less than 50 mL/minute).

Probenecid is administered orally.

Adverse GI effects may be minimized by taking the drug with food or antacids; dosage reduction may be required.

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.

Oat3 Inhibitors/Ketorolac

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 organic anion transporter 3 (OAT3) may inhibit the renal clearance of ketorolac.

CLINICAL EFFECTS: Enhanced ketorolac toxicity including gastrointestinal and renal toxicity as well as increased risk of bleeding.

PREDISPOSING FACTORS: 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: Concomitant administration of ketorolac and organic anion transporter 3 (OAT3) inhibitors are contraindicated by the manufacturer. If concurrent therapy is deemed medically necessary, 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: Probenecid has been reported to increase serum concentrations and toxicity of nonsteroidal anti-inflammatory drugs (e.g., indomethacin, ketoprofen, naproxen).(1-3) Based upon material from the manufacturer of ketorolac, concurrent administration of probenecid and ketorolac also increases serum concentrations of the NSAID ketorolac and produces a 2-fold increase in the half-life of ketorolac and a 3-fold increase in the area under the plasma concentration-time curve.(4) Ketorolac is a potent NSAID analgesic and increasing the serum concentrations may increase the risk of occurrence of serious renal, GI and hematologic side effects. OAT3 inhibitors linked to this monograph include: cabotegravir, leflunomide, nitisinone, probenecid, teriflunomide, and vadadustat.(5)

Oat3 Inhibitors/Sodium Phenylbutyrate-Taurursodiol

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 organic anion transporter 3 (OAT3) may inhibit the renal elimination of conjugated sodium phenylbutyrate and sodium phenylbutyrate metabolites.(1,2)

CLINICAL EFFECTS: Concurrent use of organic anion transporter 3 (OAT3) inhibitors may result in an increase in both the therapeutic and toxic effects of sodium phenylbutyrate.(1,2)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of sodium phenylbutyrate-taurursodiol (sodium phenylbutyrate-ursodoxicoltaurine) states that concurrent use with organic anion transporter 3 (OAT3) inhibitors should be avoided.(1) The Canadian manufacturer of sodium phenylbutyrate-taurursodiol states that OAT3 inhibitors should not be used with sodium phenylbutyrate-taurursodiol.(2)

DISCUSSION: Probenecid may inhibit the renal elimination of conjugated sodium phenylbutyrate and sodium phenylbutyrate metabolites.(1,2) OAT3 inhibitors linked to this monograph include: cabotegravir, leflunomide, nitisinone, probenecid, teriflunomide, and vadadustat.(3)

Probenecid/Seladelpar

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: Probenecid may inhibit the renal elimination of seladelpar.(1,2)

CLINICAL EFFECTS: Concurrent use of probenecid may result in an increase in both the therapeutic and toxic effects of seladelpar, such as hepatotoxicity.(1) Symptoms can include nausea, vomiting, jaundice, dark urine, abdominal pain, and unexplained fatigue.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of seladelpar states that concurrent administration of seladelpar with probenecid should be avoided.(1)

DISCUSSION: In a study in healthy subjects, concurrent administration of seladelpar (single 10 mg dose) with probenecid (500 mg) resulted in approximately a 2-fold increase in area-under-curve (AUC) and a 4.69-fold increase in concentration maximum (Cmax) of seladelpar.(1)

Ugt Inhibitors/Lorazepam Extended Release

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 UDP-glucuronosyltransferases (UGT) may inhibit the metabolism of lorazepam.(1)

CLINICAL EFFECTS: Concurrent use of UGT inhibitors may result in increased exposure to and toxicity from lorazepam, including profound sedation, respiratory depression, and coma.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of lorazepam extended release capsules states the initiating a UGT inhibitor during therapy with lorazepam extended release capsules should be avoided. If a UGT inhibitor is initiated, discontinue lorazepam extended release capsules and switch patient to a reduced dose of lorazepam tablets during concurrent therapy.(1)

DISCUSSION: In a study in 8 healthy males, pretreatment with valproate (250 mg twice daily for 3 days) decreased the total clearance of a single dose of lorazepam (2 mg intravenously) by 40% in 6 subjects. The formation rate of lorazepam glucuronide was decreased by 55% in these subjects. Lorazepam concentrations were about 2-fold higher for at least 12 hours post-dose during concurrent valproate.(2,4) In a randomized, double-blind, placebo-controlled study in 16 healthy males, concurrent divalproex (500 mg every 12 hours for 12 days) increased the area-under-curve (AUC), maximum concentration (Cmax), and minimum concentration (Cmin) of lorazepam (1 mg every 12 hours, Days 6-10) by 20%, 8%, and 31%, respectively. Lorazepam clearance was decreased by 31% during concurrent divalproex.(5) There is one case report of coma following the injection of 6 mg of lorazepam over 24 hours in a patient maintained on valproate (1000 mg). The patient remained in a coma for between 48 and 72 hours.(6) In a study in 9 healthy subjects, pretreatment with probenecid (500 mg every 6 hours) increased the half-life (T1/2) of a single intravenous dose of lorazepam (2 mg) by 130%. Lorazepam clearance was decreased by 45%. There was no change in lorazepam apparent volume of distribution.(2,7) UGT inhibitors linked to this monograph include: atazanavir, belumosudil, capivasertib, erlotinib, gemfibrozil, indinavir, ketoconazole, lapatinib, mefenamic acid, nilotinib, pazopanib, probenecid, regorafenib, sorafenib, and valproic acid.

Ugt1a1 Inhibitors/Irinotecan

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 UGT1A1 may inhibit the metabolism of SN-38, the active metabolite of irinotecan.(1) Atazanavir may inhibit the metabolism of irinotecan by UGT1A1.(1,2) This increases the system exposure to SN-38, the active metabolite of irinotecan.(3)

CLINICAL EFFECTS: Concurrent use of UGT1A1 inhibitors may result in increased exposure to and toxicity from irinotecan.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of irinotecan states do not administer UGT1A1 inhibitors with irinotecan unless there are no therapeutic alternatives. The increased exposure to the active metabolite should be taken into consideration when co-administering these agents.(1) The US manufacturer of atazanavir states that concurrent use of irinotecan is contraindicated.(2) The Australian manufacturer of atazanavir states that irinotecan should not be administered with atazanavir.(3)

DISCUSSION: Because atazanavir inhibits UGT1A1 at therapeutic concentrations, it is expected to interfere with the metabolism of irinotecan. Therefore, the manufacturer of atazanavir states that irinotecan should not be administered with atazanavir.(1,2) UGT1A1 inhibitors linked to this monograph include: atazanavir, capivasertib, belumosudil, erlotinib, gemfibrozil, lapatinib, nilotinib, pazopanib, probenecid, regorafenib, and sorafenib. One or more of the drug pairs linked to this monograph have been included in a list of interactions that should be considered "high-priority" for inclusion and should not be inactivated in EHR systems. This DDI subset was vetted by an expert panel commissioned by the U.S. Office of the National Coordinator (ONC) for Health Information Technology.

Ugt1a1 Inhibitors/Sacituzumab Govitecan

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 UGT1A1 may inhibit the metabolism of SN-38, the topoisomerase inhibitor which is the antineoplastic component of sacituzumab govitecan.(1)

CLINICAL EFFECTS: Concurrent use of UGT1A1 inhibitors may result in increased exposure to and toxicity from sacituzumab govitecan. Toxicities from sacituzumab govitecan include neutropenia, severe diarrhea, nausea, and vomiting.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Avoid the use of inhibitors of UGT1A1 in patients receiving sacituzumab govitecan.(1)

DISCUSSION: SN-38, the small molecule moiety of sacituzumab govitecan, is metabolized by UGT1A1, and inhibitors of UGT1A1 are expected to increase SN-38 levels and dose limiting toxicities.(1) In a clinical trial, patients homozygous for decreased function UGT1A1*28 allele had a 26% incidence of Grade 4 neutropenia, compared to 13% of patients heterozygous for the UGT1A1*28 allele and 11% of patients homozygous for the wild type allele.(1) Coadministration of ketoconazole (a CYP3A4 and UGT1A1 inhibitor) with irinotecan, has been reported to result in increased exposure to SN-38, an active metabolite of irinotecan.(2) UGT1A1 inhibitors linked to this monograph include: atazanavir, belumosudil, capivasertib, erlotinib, gemfibrozil, indinavir, ketoconazole, lapatinib, nilotinib, pazopanib, probenecid, regorafenib, and sorafenib.

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

Oat1 And Oat3 Inhibitors/Selected Carbapenem Antibiotics

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

MECHANISM OF ACTION: Inhibitors of organic anion transporter 1 (OAT1) and organic anion transporter 3 (OAT3) may inhibit the renal excretion of doripenem(1), meropenem(2), and tebipenem(3) by competing with them for active tubular secretion.

CLINICAL EFFECTS: Concurrent use of OAT1 and OAT3 inhibitors may result in elevated levels of and toxicity from doripenem(1), meropenem(2) or tebipenem.(3)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of doripenem states that concurrent use of OAT1 and OAT3 inhibitors is not recommended.(1) The US manufacturer of meropenem states that concurrent use of OAT1 and OAT3 inhibitors is not recommended.(2) The US manufacturer of tebipenem states concurrent use of tebipenem and OAT1 and OAT3 inhibitors is generally not recommended. If concurrent use with tebipenem is necessary, monitor more frequently for adverse reactions associated with tebipenem, such as diarrhea and headache.(3)

DISCUSSION: Probenecid has been shown to increase doripenem half-life (T1/2) and area-under-curve (AUC) by 53% and 75%, respectively.(1) In a study in six subjects, concurrent probenecid increased meropenem T1/2 by 33%.(4) Other studies have shown probenecid to increase the T1/2 of meropenem by 38% and the extent of meropenem systemic exposure by 58%.(2) In a study, coadministration of a single oral dose of 250 mg of tebipenem pivoxil with probenecid (OAT1 and OAT3 inhibitor) increased tebipenem maximum concentration (Cmax) by approximately 1.5-fold and plasma area-under-curve (AUC) by approximately 2.9-fold.(3) OAT1 inhibitors linked to this monograph include: cabotegravir and probenecid. OAT3 inhibitors linked to this monograph include: cabotegravir, leflunomide, nitisinone, probenecid, teriflunomide, and vadadustat.(5)

Oat3 Inhibitors/Baricitinib

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

MECHANISM OF ACTION: Inhibitors of organic anion transporter 3 (OAT3) may inhibit the renal elimination of baricitinib.(1,2)

CLINICAL EFFECTS: Concurrent use of organic anion transporter 3 (OAT3) inhibitors may result in an increase in both the therapeutic and toxic effects of baricitinib.(1,2)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: If concurrent therapy with a strong organic anion transporter 3 (OAT3) inhibitor is warranted, and the recommended dosage is 4 mg once daily, reduce to 2 mg once daily. If the recommended dosage is 2 mg once daily, reduce dose to 1 mg once daily. If the recommended dosage is 1 mg once daily, consider discontinuing probenecid.(2) OAT3 inhibitors with less inhibitor potency are not expected to cause a clinically significant change in baricitinib levels.(1,2)

DISCUSSION: In a clinical pharmacology study, dosing of probenecid (an OAT3 inhibitor with strong inhibition potential) resulted in approximately a 2-fold increase in area-under-curve (AUC) with no change in time maximum (Tmax) or concentration maximum (Cmax) of baricitinib.(1,2) OAT3 inhibitors linked to this monograph include: cabotegravir, nitisinone, probenecid and vadadustat.(1-3)

Oat3 Inhibitors/Methotrexate(Oncology-Inj)

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

MECHANISM OF ACTION: Inhibitors of organic anion transporter 3 (OAT3) may inhibit the renal elimination of methotrexate.

CLINICAL EFFECTS: Concurrent use of organic anion transporter 3 (OAT3) inhibitors may result in an increase in both the therapeutic and toxic effects of methotrexate, leading to increased risk of severe neurotoxicity, stomatitis, and myelosuppression, including neutropenia.

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

PATIENT MANAGEMENT: If coadministration cannot be avoided, monitor closely for methotrexate adverse reactions.

DISCUSSION: Concomitant administration of methotrexate and probenecid has been shown to increase methotrexate plasma levels two to four times higher than when methotrexate is administered alone.(2-5) OAT3 inhibitors linked to this monograph include: cabotegravir, nitisinone, probenecid and vadadustat.(7)

Oat3 Inhibitors/Pemetrexed

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

MECHANISM OF ACTION: Inhibitors of organic anion transporter 3 (OAT3) may inhibit the renal elimination of pemetrexed.

CLINICAL EFFECTS: Concurrent use of organic anion transporter 3 (OAT3) inhibitors may result in an increase in both the therapeutic and toxic effects of pemetrexed, including myelosuppression, neutropenia, renal toxicity, and gastrointestinal toxicity.

PREDISPOSING FACTORS: This interaction is expected to be more severe in patients with mild to moderate renal function insufficiency (creatinine clearance (CrCl) of 45 ml/min to 79 ml/min).

PATIENT MANAGEMENT: Avoid concomitant administration of OAT3 inhibitors before and after administration of pemetrexed when possible. If concomitant administration cannot be avoided, monitor patients more frequently for myelosuppression, renal, and gastrointestinal toxicity.

DISCUSSION: In patients with normal renal function, ibuprofen (400 mg 4 times daily) decreased the clearance of pemetrexed by 20% and increased its area-under-curve (AUC) by 20%.(1) In two randomized, controlled cross-over trials, 27 cancer patients with a creatinine clearance (CrCl) less than or equal to 60 ml/min received pemetrexed (500 mg/m2) infusion on Day 1 of a 21-day cycle and either aspirin 325 mg or ibuprofen 400 mg orally every 6 hours starting 2 days before pemetrexed administration. Ibuprofen decreased the clearance of pemetrexed by 16%, increased its maximum concentration (Cmax) by 15%, and increased the AUC by 20%.(2) OAT3 inhibitors linked to this monograph include: cabotegravir, nitisinone, probenecid, and vadadustat.(3)

Probenecid/Pralatrexate

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

MECHANISM OF ACTION: Inhibitors of multidrug resistance-associated protein 2 (MRP2) such as probenecid may inhibit the renal elimination of pralatrexate.(1)

CLINICAL EFFECTS: Concurrent use of probenecid with pralatrexate may result in an increase in both the therapeutic and toxic effects of pralatrexate, leading to increased risk of severe neurotoxicity, stomatitis, and myelosuppression, including neutropenia.

PREDISPOSING FACTORS: Patients with severe renal impairment (eGFR 15 to < 30 mL/min/1.73 m2) may be at greater risk for increased exposure and adverse reactions.

PATIENT MANAGEMENT: Administration of probenecid with pralatrexate should be avoided.(1) If coadministration is unavoidable, monitor for increased risk of adverse reactions.

DISCUSSION: Concurrent administration of probenecid resulted in delayed clearance of pralatrexate and increased pralatrexate exposure.(1)

Ugt1a1 Inhibitors/Belinostat

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

MECHANISM OF ACTION: Inhibitors of UGT1A1 may inhibit the metabolism of belinostat.(1)

CLINICAL EFFECTS: Concurrent use of UGT1A1 inhibitor may result in increased exposure to and toxicity from belinostat. Toxicities from belinostat include thrombocytopenia, neutropenia, anemia, infections, hepatotoxicity, and gastrointestinal toxicity.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Avoid the use of UGT1A1 inhibitors in patients receiving belinostat. If concurrent use cannot be avoided, a dose reduction by 25% is recommended as follows: -If starting dose is 1,000 mg/m2 - reduce dose to 750 mg/m2 -If starting dose is 750 mg/m2 - reduce dose to 562.5 mg/m2 -If starting dose is 500 mg/m2 - interrupt belinostat treatment for the duration of the UGT1A1 inhibitor. After discontinuation of the UGT1A1 inhibitor for 5 half-lives, resume belinostat at the dosage that was taken prior to the UGT1A1 inhibitor.(1) If concurrent use is required, the dose of belinostat may need to be reduced in response to dose-limiting toxicities. The manufacturer of belinostat recommends a 25% dose reduction (to 750 mg/m2) in patients who are homozygous for the UGT1A1*28 allele.(1)

DISCUSSION: Belinostat is primarily metabolized by UGT1A1 and inhibitors of UGT1A1 are expected to increase belinostat levels and dose limiting toxicities.(1) In a PKPB model, belinostat half-life increased by 1.5-fold, area-under-curve (AUC) increased by 1.4-fold, concentration maximum (Cmax) decreased by 33%, and renal excretion increased by 2.5-fold following administration with atazanavir (UGT1A1 inhibitor).(1) UGT1A1 inhibitors linked include: atazanavir, belumosudil, capivasertib, erlotinib, gemfibrozil, indinavir, ketoconazole, lapatinib, nilotinib, pazopanib, probenecid, regorafenib, and sorafenib.

Ugt1a4 Inhibitors/Pexidartinib

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

MECHANISM OF ACTION: Inhibitors of UGT1A4 may inhibit the metabolism of pexidartinib.(1)

CLINICAL EFFECTS: Concurrent use of a inhibitors of UGT1A4 may result in elevated levels and increased effects of pexidartinib, such as hepatotoxicity.(1,2) Symptoms can include nausea, vomiting, jaundice, dark urine, abdominal pain, and unexplained fatigue.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of pexidartinib states that pexidartinib coadministration with inhibitors of UGT1A4 should be avoided.(1) If coadministration with a UGT1A4 inhibitor cannot be avoided, reduce the pexidartinib dose according to the following recommendations. If the planned total daily dose is currently 500 mg, modify the total daily dose to 250 mg by administering 125 mg twice daily. If the planned total daily dose is currently 375 mg, modify the total daily dose to 250 mg by administering 125 mg twice daily. If the planned total daily dose is currently 250 mg, modify the total daily dose to 125 mg by administering 125 mg once daily. If concomitant use of a UGT1A4 inhibitor is discontinued, increase the pexidartinib dose to the dose that was used before starting the inhibitor after three plasma half-lives of the UGT1A4 inhibitor. Monitor liver tests, including AST, ALT, total bilirubin, direct bilirubin, ALP and gamma-glutamyltransferase (GGT) according to the recommendations in the Turalio package insert. Advise patients to immediately report any symptoms of hepatotoxicity.

DISCUSSION: Coadministration of probenecid (UGT1A4 inhibitor) increased pexidartinib maximum concentration (Cmax) and area-under-the-curve (AUC) by 5% and 60%.(1) Inhibitors of UGT1A4 linked to this monograph include: probenecid.(1,2)

Ugt1a4 Inhibitors/Pexidartinib (200 Mg)

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

MECHANISM OF ACTION: Inhibitors of UGT1A4 may inhibit the metabolism of pexidartinib.(1)

CLINICAL EFFECTS: Concurrent use of a inhibitors of UGT1A4 may result in elevated levels and increased effects of pexidartinib, such as hepatotoxicity.(1,2) Symptoms can include nausea, vomiting, jaundice, dark urine, abdominal pain, and unexplained fatigue.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of pexidartinib states that pexidartinib coadministration with inhibitors of UGT1A4 should be avoided.(1) If coadministration with a UGT1A4 inhibitor cannot be avoided, reduce the pexidartinib dose according to the following recommendations. If the planned total daily dose is currently 800 mg, modify the total daily dose to 400 mg by administering 200 mg twice daily. If the planned total daily dose is currently 600 mg, modify the total daily dose to 400 mg by administering 200 mg twice daily. If the planned total daily dose is currently 400 mg, modify the total daily dose to 200 mg by administering 200 mg once daily. If concomitant use of a UGT1A4 inhibitor is discontinued, increase the pexidartinib dose to the dose that was used before starting the inhibitor after three plasma half-lives of the UGT1A4 inhibitor. Monitor liver tests, including AST, ALT, total bilirubin, direct bilirubin, ALP and gamma-glutamyltransferase (GGT) according to the recommendations in the Turalio package insert. Advise patients to immediately report any symptoms of hepatotoxicity.

DISCUSSION: Coadministration of probenecid (UGT1A4 inhibitor) increased pexidartinib maximum concentration (Cmax) and area-under-the-curve (AUC) by 5% and 60%.(1) Inhibitors of UGT1A4 linked to this monograph include: probenecid.(1,2)

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

Oat3 Inhibitors/Methotrexate (Low Strength Inj, Oral)

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

MECHANISM OF ACTION: Inhibitors of organic anion transporter 3 (OAT3) may inhibit the renal elimination of methotrexate.

CLINICAL EFFECTS: Concurrent use of organic anion transporter 3 (OAT3) inhibitors may result in an increase in both the therapeutic and toxic effects of methotrexate, leading to increased risk of severe neurotoxicity, stomatitis, and myelosuppression, including neutropenia.

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

PATIENT MANAGEMENT: If concurrent use cannot be avoided, monitor methotrexate blood levels closely and adjust the dose accordingly.

DISCUSSION: Concomitant administration of methotrexate and probenecid has been shown to increase methotrexate plasma levels two to four times higher than when methotrexate is administered alone. OAT3 inhibitors linked to this monograph include: cabotegravir, nitisinone, probenecid and vadadustat.(7)

Probenecid/Dyphylline

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

MECHANISM OF ACTION: It appears that probenecid reduces the renal excretion rate of dyphylline.

CLINICAL EFFECTS: Increased serum levels of dyphylline.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: If both drugs are given, adjust the dyphylline dose as needed based on serum dyphylline levels and patient response.

DISCUSSION: Additional documentation is necessary to confirm this potential interaction. Since theophylline is eliminated by hepatic metabolism rather than renal excretion, it is recommended as an alternative to dyphylline when probenecid is given concurrently. However, the benefits of using this combination may outweigh the risks, especially in cases of theophylline intolerance. Professional judgement should be exercised.

Probenecid/Pyrazinamide

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

MECHANISM OF ACTION: Pyrazinamide has been shown to inhibit urate secretion.(1)

CLINICAL EFFECTS: May observe hyperuricemia and gout resulting from reduced probenecid response.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Monitor patients receiving concurrent probenecid and pyrazinamide for signs and symptoms of gout flares.

DISCUSSION: In a study in 18 males, pyrazinamide inhibited urate secretion, but had no effect on probenecid secretion.(1)

Probenecid/Selected Cephalosporins & Penicillins

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

MECHANISM OF ACTION: Probenecid impairs the clearance of some cephalosporins and penicillins via inhibition of renal anion transporters in the proximal tubule.(49) It has also been hypothesized that probenecid may affect tissue distribution of cephalosporins.(1-5)

CLINICAL EFFECTS: The concurrent administration of probenecid may result in increased maximum concentration (Cmax), area-under-curve (AUC), and half-life of the cephalosporin or penicillin.(49) While this may improve antibiotic efficacy,(46-48) increased levels may also increase the risk for antibiotic-associated nephrotoxicity.(4)

PREDISPOSING FACTORS: Underlying renal dysfunction may increase the risk for nephrotoxicity.

PATIENT MANAGEMENT: In patients receiving the combination to improve antibiotic efficacy, monitor for antibiotic adverse effects and consider monitoring renal function. In patients receiving probenecid therapy to prevent or treat hyperuricemia, exposure to the antibiotic will be increased. A decrease in antibiotic dose or frequency may be required. The US manufacturer of piperacillin-tazobactam states probenecid should not be coadministered with piperacillin-tazobactam unless the benefit outweighs the risk.(50)

DISCUSSION: Concurrent use of probenecid with a cephalosporin or penicillin may cause an increase in the Cmax, AUC, and an increased elimination half life of the antibiotic.(6-8,49) This may be beneficial or necessary in difficult to treat infections,(46-48) but an increased risk for adverse effects should be expected. Antibiotics not dose adjusted for concurrent use with probenecid may be associated with an increased risk for adverse effects, such as nephrotoxicity. Probenecid administered concurrently with piperacillin-tazobactam prolongs the half-life of piperacillin by 21% and tazobactam by 71%. In a study in 8 healthy males, concurrent administration of probenecid (1 g) with piperacillin (1 g IM) increased piperacillin's Cmax and AUC by 30% and 60%. Renal clearance was reduced by 40%.(51) The cephalosporins affected by probenecid include cefazolin,(9-11) cephacetrile,(12,13) cephaloglycin,(14,15) cephalexin,(16-21) cephradine, (22-23) cefoxitin,(24-28) cefadroxil(29), cefaclor,(23) cefamandole,(30) ceftizoxime,(31,32) cefuroxime,(33,34) cefprozil,(35) cefonicid,(36) cefmetazole,(37) cefmenoxime,(38) and cefditoren.(39) Probenecid has been shown not to affect moxalactam,(4,40,41) ceforanide, (4,42), cefoperazone, ceftazidime(4,34,43) or ceftriaxone.(4)

Probenecid/Selected Nsaids

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

MECHANISM OF ACTION: Probenecid may inhibit the renal tubular secretion of some NSAIDs. Probenecid may also prevent biliary clearance of NSAIDs.

CLINICAL EFFECTS: The decreased clearance of NSAIDs may lead to increased blood levels and an increase in adverse effects.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Patients receiving concurrent therapy should be monitored for an increase in NSAID-related adverse effects, including renal insufficiency. The dose of the NSAID may need to be decreased or probenecid may need to be discontinued.

DISCUSSION: Probenecid has been reported to increase the blood levels of indomethacin by 2-fold to 6-fold.(1,2) Probenecid has been reported to increase levels of oral ketoprofen by 93%;(3) however, no effect was seen on intramuscular ketoprofen in another study.(4) Probenecid has also been shown to increase naproxen levels.(5) Probenecid has been shown to increase the maximum concentration (Cmax) of tenoxicam. No other pharmacokinetic parameters were affected.(6) This interaction may result in clinical benefits in some patients.

Probenecid/Zidovudine

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

MECHANISM OF ACTION: Inhibition of zidovudine metabolism by probenecid.

CLINICAL EFFECTS: Increased serum zidovudine levels and cutaneous reactions with systemic symptoms (eg, fever, malaise, myalgia,) have been reported.

PREDISPOSING FACTORS: There may be an increased tendency of patients with disorders of the immune system to develop adverse reaction to these drugs.

PATIENT MANAGEMENT: Observe patient for unexpected cutaneous reactions. It may be necessary to reduce the dosing frequency of zidovudine if probenecid is administered concurrently.

DISCUSSION: Concomitant administration of zidovudine and probenecid may be therapeutically beneficial in reducing the daily dose of zidovudine. However, because of the narrow therapeutic index of zidovudine, the frequent need to treat patients with immune system disorders with various additional drugs, and the known ability of probenecid to inhibit metabolism or renal excretion of many drugs, would make combined zidovudine/probenecid treatment difficult to manage in many of these type of patients. Cutaneous reactions have been reported in many patients receiving zidovudine and probenecid concurrently.

Ugt Inhibitors/Lorazepam; Mexazolam

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

MECHANISM OF ACTION: Inhibitors of UDP-glucuronosyltransferases (UGT) may inhibit the metabolism of lorazepam.(1-4) One of the active metabolites of mexazolam is lorazepam.

CLINICAL EFFECTS: Concurrent use of UGT inhibitors may increase levels of and clinical effects from lorazepam, including profound sedation, respiratory depression, and coma.(1-4)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturers of lorazepam state that the dosage of lorazepam should be reduced by 50% in patients receiving UGT inhibitors.(1,2)

DISCUSSION: In a study in 9 healthy subjects, pretreatment with probenecid (500 mg every 6 hours) increased the half-life (T1/2) of a single intravenous dose of lorazepam (2 mg) by 130%. Lorazepam clearance was decreased by 45%. There was no change in lorazepam apparent volume of distribution.(1,4) In 7 patients given probenecid 1G orally one hour prior to induction anesthesia with midazolam, there was no significant change in plasma protein binding due to probenecid pretreatment. The mean free midazolam fractions were 3.31% prior and 3.34% following pretreatment.(5) UGT inhibitors linked to this monograph include: atazanavir, belumosudil, capivasertib, erlotinib, gemfibrozil, indinavir, ketoconazole, lapatinib, mefenamic acid, nilotinib, pazopanib, probenecid, regorafenib, and sorafenib.

Uricosurics/Aspirin (>100 Mg); Salicylates

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

MECHANISM OF ACTION: Not clearly established. Protein binding displacement is a possibility.

CLINICAL EFFECTS: May observe hyperuricemia and gout resulting from reduced uricosuric response.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Avoid chronic, moderate to high doses of salicylates.

DISCUSSION: This interaction is well documented. Occasional small doses of salicylates do not appear to inhibit the action of uricosurics.

There is no enhanced messaging for this drug.

• Chronic kidney disease stage 4 (severe) GFR 15-29 ml/min
• Chronic kidney disease stage 5 (failure) GFr<15 ml/min
• Hemolytic anemia from pyruvate kinase and g6PD deficiencies
• Urate renal calculi
• Uric acid nephropathy

• Peptic ulcer

There are no moderate contraindications for this drug.

There is no enhanced messaging for this drug.

Less Frequent

• Urate renal calculi

Rare or Very Rare

• Allergic dermatitis
• Anaphylaxis
• Anemia
• Angioedema
• Aplastic anemia
• Back pain
• Chest tightness
• Drug fever
• Dyspnea
• Erythema
• Hemolytic anemia
• Hepatic necrosis
• Leukopenia
• Nephrotic syndrome
• Pruritus of skin
• Renal colic
• Rib pain
• Skin rash
• Uric acid nephropathy
• Urticaria
• Wheezing

More Frequent

• Acute gouty arthritis
• Anorexia
• Headache disorder
• Nausea
• Vomiting

Less Frequent

• Dizziness
• Flushing
• Gingival pain
• Increased urinary frequency

No enhanced messaging available.

No enhanced messaging available.

Probenecid crosses the placenta and has been detected in cord blood. The risks and benefits of probenecid should be evaluated when considering use of the drug in women of childbearing potential.

Probenecid is expected to be distributed into human milk; possible effects on nursing infants are not known. The drug should be used with caution in breast-feeding women because of potential risks to nursing infants.

No enhanced messaging available.