Phosphate Laxative (sodium phosphate,monobasic/sodium phosphate,dibasic)

Saline laxatives should be administered only at infrequent intervals. Most studies suggest that the minimum effective oral laxative dose of magnesium is 80 mEq. The usual dosages of the various saline laxatives are below; for dosages in children younger than the ages listed, a physician should be consulted.

For precautions that should be considered before administration of saline laxatives in patients susceptible to adverse effects, see Cautions: Saline Laxatives, in the Cathartics and Laxatives General Statement 56:12.

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

Oral Phosphates; Active Vitamin D Analogs/Burosumab

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 burosumab and phosphates or vitamin D may increase serum phosphate levels. This combination may lead to greater increases in serum phosphate than anticipated.

CLINICAL EFFECTS: The combination of burosumab with oral phosphates or active vitamin D analogs may result in hyperphosphatemia and may increase the risk of nephrocalcinosis.(1)

PREDISPOSING FACTORS: Patients with renal impairment have alterations in mineral metabolism that may increase the risk of hyperphosphatemia.(1)

PATIENT MANAGEMENT: The concomitant use of burosumab with oral phosphates or active vitamin D analogs is contraindicated. Discontinue oral phosphate and/or active vitamin D analogs one week before starting burosumab.(1)

DISCUSSION: Burosumab restores dysfunctional renal phosphate reabsorption and renal production of 1,25-dihydroxyvitamin D to treat X-linked hypophosphatemia. Additional oral phosphates and/or active vitamin D analogs may raise serum phosphate higher than anticipated.

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

Laxatives/Trofinetide

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

MECHANISM OF ACTION: Trofinetide commonly causes diarrhea of mild to moderate severity. Laxatives may increase the incidence or severity of diarrhea.(1)

CLINICAL EFFECTS: Concurrent use of laxatives with trofinetide may increase the risk of severe diarrhea.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Patients should stop laxatives before starting trofinetide. If diarrhea occurs, consider anti-diarrheal treatment and monitor hydration status. If severe diarrhea or dehydration occurs, interrupt, reduce dose, or discontinue trofinetide.(1)

DISCUSSION: In clinical trials, 85% of patients on trofinetide developed diarrhea. Concurrent use of laxatives may increase this risk.(1)

Laxatives; Stool Softeners/Tenapanor

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

MECHANISM OF ACTION: Tenapanor commonly causes diarrhea of mild to moderate severity. Laxatives and stool softeners may increase the incidence or severity of diarrhea.(1)

CLINICAL EFFECTS: Concurrent use of laxatives or stool softeners with tenapanor may increase the risk of severe diarrhea.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The US manufacturer of tenapanor states that patients should be instructed to avoid stool softeners and laxatives with tenapanor. If severe diarrhea occurs, tenapanor should be discontinued.(1)

DISCUSSION: In clinical trials, 43-53% of CKD patients on dialysis treated with tenapanor developed diarrhea. Diarrhea usually occurred soon after treatment initiation and was severe in 5% of patients.(1)

Oral Phosphate Supplements; Urinary Ph Modifiers/Alum;Ca;Mag

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

MECHANISM OF ACTION: Medications containing significant amounts of aluminum, calcium, or magnesium may bind to the phosphate and prevent its absorption.(1)

CLINICAL EFFECTS: Concurrent use of medications containing significant amounts of aluminum, calcium, or magnesium may result in decreased effectiveness of phosphate supplements and urinary pH modifiers high in phosphate.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Patients receiving phosphate supplements or urinary pH modifiers high in phosphate should be instructed to avoid medications containing aluminum, calcium, or magnesium.(1) If concurrent use cannot be avoided, separate the administration of phosphate containing products by as much time as possible from medications containing aluminum, calcium, or magnesium. Some phosphate laxative products used as phosphate supplements may contain sufficient quantities of phosphate to interact as well.

DISCUSSION: The manufacturer of K-Phos states that products containing aluminum, calcium, or magnesium may bind to the phosphate and prevent its absorption. Therefore, patients receiving phosphate supplements and urinary pH modifiers high in phosphate should be instructed to avoid products containing aluminum, calcium, or magnesium.(1)

Serum Phosphate Level-Altering Drugs/Erdafitinib

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

MECHANISM OF ACTION: Medications that alter serum phosphate may interfere with interpretation of phosphate levels that are needed to determine initial erdafitinib dose.(1)

CLINICAL EFFECTS: Serum phosphate levels that are elevated by concomitant medications may result in an inappropriately low dose and decreased effectiveness of erdafitinib. Serum phosphate levels that are decreased by concomitant medications may result in an inappropriately high dose and increased toxicity from erdafitinib.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: The manufacturer of erdafitinib states that agents that alter serum phosphate levels should be avoided before the initial dose increase period for erdafitinib based on serum phosphate levels (days 14 to 21).(1)

DISCUSSION: Concomitant administration of serum phosphate level-altering agents during the initial dose increase period of erdafitinib based on serum phosphate levels (days 14 to 21) may interfere with serum phospate levels and lead to incorrect dosing of erdafitinib.(1) Agents that may alter serum phosphate levels linked to this monograph include: aluminum carbonate, aluminum hydroxide, calcium acetate, calcium carbonate, calcium citrate, cod liver oil, ferric citrate, lanthanum, magnesium carbonate, magnesium hydroxide, potassium phosphate, sevelamer, sodium phosphate, sucroferric oxyhydroxide, tenapanor, and vitamin D.(1)

Sodium Phosphate Bowel Cleanser/Ace Inhibitors; Arbs

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

MECHANISM OF ACTION: Bowel cleansing with sodium phosphate causes dehydration, decreased intravascular volume and hyperphosphatemia, which increases phosphate levels in the renal tubules. Abnormally high levels of calcium and phosphate in the renal tubules may precipitate out, resulting in renal injury.(1)

CLINICAL EFFECTS: Use of sodium phosphate for bowel cleansing in patients maintained on angiotensin converting enzyme (ACE) inhibitors, angiotension receptor blockers (ARBs) may increase the risk of acute phosphate nephropathy, which is an acute kidney injury associated with deposits of calcium phosphate crystal in the renal tubules that may result in permanent renal function impairment. Acute phosphate nephropathy presents as acute kidney injury with minimal proteinuria and a bland urine sediment.(2) Use of sodium phosphate products at laxative doses has not been associated with acute kidney injury.(3)

PREDISPOSING FACTORS: Patients who may be at an increased risk of acute phosphate nephropathy include those who are over age 55; are hypovolemic or have decreased intravascular volume; have baseline kidney disease, bowel obstruction, or active colitis; and who are using medications that affect renal perfusion or function (such as diuretics, ACE inhibitors, ARBs, and possibly nonsteroidal anti-inflammatory drugs (NSAIDs).(2)

PATIENT MANAGEMENT: If possible, use an alternative agent for bowel cleansing.(1) Use sodium phosphate products with caution in patients taking medications that affect kidney function or perfusion, such as ACE inhibitors or ARBs. Obtain baseline and post-procedure labs (electrolytes, calcium, phosphate, BUN, creatinine, and [in smaller, frail individuals] glomerular filtration rate). Instruct patients to drink sufficient quantities of clear fluids before, during, and after bowel cleansing and to avoid other laxatives that contain sodium phosphate. Consider hospitalization and intravenous hydration during bowel cleansing to support frail patients who may be unable to drink an appropriate volume of fluid or who may be without assistance at home.(2) Use of an electrolyte solution for rehydration may decrease the risk of acute phosphate nephropathy.(4,5)

DISCUSSION: Since May 2006, the FDA has received 20 reports of acute phosphate nephropathy associated with the use of Osmo Prep. Concomitant medications included ACE inhibitors or ARBs (11), diuretics (6), and NSAIDs (4).(2) In a retrospective review of colonoscopy patients, simultaneous use of ACE inhibitors or ARBs significantly increased the risk of acute kidney injury from oral sodium phosphate. Diuretic use was also a risk factor.(6) In a case series study of 21 cases of acute phosphate nephropathy in patients who had used oral sodium phosphate, 14 patients received an ACE inhibitor or ARB, 4 used a diuretic, and 3 used an NSAID.(7) Cases have also been reported with rectal products.(8)

Sodium Phosphate Bowel Cleanser/Diuretics

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

MECHANISM OF ACTION: Bowel cleansing with sodium phosphate causes dehydration, decreased intravascular volume and hyperphosphatemia, which increases phosphate levels in the renal tubules. Abnormally high levels of calcium and phosphate in the renal tubules may precipitate out, resulting in renal injury.(1)

CLINICAL EFFECTS: Use of sodium phosphate for bowel cleansing in patients maintained on diuretics may increase the risk of acute phosphate nephropathy, which is an acute kidney injury associated with deposits of calcium phosphate crystal in the renal tubules that may result in permanent renal function impairment. Acute phosphate nephropathy presents as acute kidney injury with minimal proteinuria and a bland urine sediment.(2) Use of oral sodium phosphate products at laxative doses has not been associated with acute kidney injury.(3)

PREDISPOSING FACTORS: Patients who may be at an increased risk of acute phosphate nephropathy include those who are over age 55; are hypovolemic or have decreased intravascular volume; have baseline kidney disease, bowel obstruction, or active colitis; and who are using medications that affect renal perfusion or function (such as diuretics, angiotensin converting enzyme (ACE) inhibitors, angiotension receptor blockers (ARBs) and possibly nonsteroidal anti-inflammatory drugs (NSAIDs).(2)

PATIENT MANAGEMENT: If possible, use an alternative agent for bowel cleansing.(1) Use sodium phosphate products with caution in patients taking medications that affect kidney function or perfusion, such as diuretics. Obtain baseline and post-procedure labs (electrolytes, calcium, phosphate, BUN, creatinine, and [in smaller, frail individuals] glomerular filtration rate). Instruct patients to drink sufficient quantities of clear fluids before, during, and after bowel cleansing and to avoid other laxatives that contain sodium phosphate. Consider hospitalization and intravenous hydration during bowel cleansing to support frail patients who may be unable to drink an appropriate volume of fluid or who may be without assistance at home.(2) Use of an electrolyte solution for rehydration may decrease the risk of acute phosphate nephropathy.(4,5)

DISCUSSION: Since May 2006, the FDA has received 20 reports of acute phosphate nephropathy associated with the use of Osmo Prep. Concomitant medications included ACE inhibitors or ARBs (11), diuretics (6), and NSAIDs (4).(2) In a retrospective review of colonoscopy patients, simultaneous use of ACE inhibitors or ARBs significantly increased the risk of acute kidney injury from oral sodium phosphate. Diuretic use was also a risk factor.(6) In a case series study of 21 cases of acute phosphate nephropathy in patients who had used oral sodium phosphate, 14 patients received an ACE inhibitor or ARB, 4 used a diuretic, and 3 used an NSAID.(7) Cases have also been reported with rectal products.(8)

Sodium Phosphate Bowel Cleanser/Nsaids; Salicylates

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

MECHANISM OF ACTION: Bowel cleansing with sodium phosphate causes dehydration, decreased intravascular volume and hyperphosphatemia, which increases phosphate levels in the renal tubules. Abnormally high levels of calcium and phosphate in the renal tubules may precipitate out, resulting in renal injury.(1)

CLINICAL EFFECTS: Use of sodium phosphate for bowel cleansing in patients maintained on nonsteroidal anti-inflammatory drugs (NSAIDs) may increase the risk of acute phosphate nephropathy, which is an acute kidney injury associated with deposits of calcium phosphate crystal in the renal tubules that may result in permanent renal function impairment. Acute phosphate nephropathy presents as acute kidney injury with minimal proteinuria and a bland urine sediment.(2) Use of oral sodium phosphate products at laxative doses has not been associated with acute kidney injury.(3)

PREDISPOSING FACTORS: Patients who may be at an increased risk of acute phosphate nephropathy include those who are over age 55; are hypovolemic or have decreased intravascular volume; have baseline kidney disease, bowel obstruction, or active colitis; and who are using medications that affect renal perfusion or function (such as diuretics, ACE inhibitors, angiotension receptor blockers [ARBs]), and NSAIDs.(2)

PATIENT MANAGEMENT: If possible, use an alternative agent for bowel cleansing.(1) Use sodium phosphate products with caution in patients taking medications that affect kidney function or perfusion, such as ACE inhibitors or ARBs. Obtain baseline and post-procedure labs (electrolytes, calcium, phosphate, BUN, creatinine, and [in smaller, frail individuals] glomerular filtration rate). Instruct patients to drink sufficient quantities of clear fluids before, during, and after bowel cleansing and to avoid other laxatives that contain sodium phosphate. Consider hospitalization and intravenous hydration during bowel cleansing to support frail patients who may be unable to drink an appropriate volume of fluid or who may be without assistance at home.(2) Use of an electrolyte solution for rehydration may decrease the risk of acute phosphate nephropathy.(4,5)

DISCUSSION: Since May 2006, the FDA has received 20 reports of acute phosphate nephropathy associated with the use of Osmo Prep. Concomitant medications included ACE inhibitors or ARBs (11), diuretics (6), and NSAIDs (4).(2) In a retrospective review of colonoscopy patients, simultaneous use of ACE inhibitors or ARBs significantly increased the risk of acute kidney injury from oral sodium phosphate. Diuretic use was also a risk factor.(6) In a case series study of 21 cases of acute phosphate nephropathy in patients who had used oral sodium phosphate, 14 patients received an ACE inhibitor or ARB, 4 used a diuretic, and 3 used an NSAID.(7) Cases have also been reported with rectal products.(8)

There are no moderate interactions for this drug.

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• Acute renal failure
• Colitis
• Gastrointestinal obstruction
• History of roux-en-Y gastric bypass
• Nephrocalcinosis
• Renal dialysis
• Torsades de pointes
• Toxic megacolon

• 30 day risk period post-myocardial infarction
• Alcohol withdrawal syndrome
• Ascites
• Cardiac arrhythmia
• Chronic heart failure
• Chronic kidney disease stage 3A (moderate) GFR 45-59 ml/min
• Chronic kidney disease stage 3B (moderate) GFR 30-44 ml/min
• Chronic kidney disease stage 4 (severe) GFR 15-29 ml/min
• Chronic kidney disease stage 5 (failure) GFr<15 ml/min
• Congenital long QT syndrome
• Coronary artery bypass graft procedure
• Debilitation
• Dehydration
• Gastric retention
• Gastrointestinal hypomotility
• Hirschsprung disease
• Hypernatremia
• Hyperparathyroidism
• Hyperphosphatemia
• Hypocalcemia
• Hypokalemia
• Hyponatremia
• Hypovolemia
• Inflammatory bowel disease
• Lower seizure threshold
• Megacolon
• Paralytic ileus
• Seizure disorder
• Seizure due to abrupt benzodiazepine withdrawal
• Severe constipation
• Unstable angina pectoris

• Cardiomyopathy
• Chronic kidney disease stage 2 (mild) GFR 60-89 ml/min
• Kidney disease with likely reduction in glomerular filtration rate (GFr)
• Predisposition to aspiration

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More Frequent

• Hypokalemia

Less Frequent

• Ulceration of colon

Rare or Very Rare

• Acidosis
• Acute renal failure
• Anaphylaxis
• Angioedema
• Bronchospastic pulmonary disease
• Dehydration
• Dyspnea
• Hypernatremia
• Hypersensitivity drug reaction
• Hypocalcemia
• Kidney disease with reduction in glomerular filtration rate (GFr)
• Nephrocalcinosis
• Seizure disorder
• Throat constriction

More Frequent

• Abdominal distension
• Acute abdominal pain
• Hyperphosphatemia
• Nausea

Less Frequent

• Dizziness
• Headache disorder
• Vomiting

Rare or Very Rare

• Cardiac arrhythmia
• Dysphagia
• Paresthesia
• Pruritus of skin
• Skin rash
• Urticaria

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