Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
RELISTOR vs BUMETANIDE
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Peripherally acting mu-opioid receptor antagonist that blocks opioid-induced constipation without affecting central analgesia.
Inhibits the Na-K-2Cl symporter (NKCC2) in the thick ascending limb of the loop of Henle, reducing reabsorption of sodium, chloride, and potassium, leading to increased urine output.
Treatment of opioid-induced constipation (OIC) in adult patients with chronic non-cancer pain,Treatment of OIC in adult patients with advanced illness who are receiving palliative care
Edema associated with congestive heart failure, hepatic cirrhosis, and renal disease,Treatment of hypertension (off-label)
0.15 mg/kg subcutaneously once daily, maximum 16 mg per dose; for opioid-induced constipation, 8 mg subcutaneously once daily.
0.5-2 mg IV/IM/PO once daily; may repeat every 6-8 hours; max 10 mg/day. Continuous IV infusion: 1 mg loading dose, then 0.5-2 mg/hour.
Terminal elimination half-life is approximately 8-10 hours in patients with normal renal function. In patients with end-stage renal disease, half-life is prolonged (~14-18 hours).
Terminal elimination half-life is approximately 1-1.5 hours in healthy adults; prolonged to 1.5-3 hours in renal impairment.
Primarily hepatic via CYP3A4 and CYP2D6 isoenzymes; also undergoes gut wall metabolism.
Primarily metabolized by the liver via cytochrome P450 (CYP) enzymes, with approximately 50% excreted unchanged in urine.
Renal excretion of unchanged drug accounts for approximately 16% of the dose; biliary/fecal excretion is the major route (approximately 54% recovered in feces).
Primarily renal (approximately 80% as unchanged drug), with minimal biliary/fecal excretion (about 10-20%).
Approximately 11-15% bound to plasma proteins (primarily albumin).
Approximately 95% bound, primarily to albumin.
Approximately 1.1 L/kg (central volume ~0.3 L/kg); indicates extensive extravascular distribution.
0.15-0.25 L/kg; indicates limited extravascular distribution, consistent with high protein binding.
Subcutaneous: approximately 82-100% (mean ~97%); oral: approximately 6% (low due to first-pass metabolism).
Oral: approximately 80-100% (mean ~90%), with a first-pass effect of about 10-20%.
For creatinine clearance <30 m L/min: 0.075 mg/kg subcutaneously every other day, maximum 8 mg per dose; not recommended in patients with end-stage renal disease requiring dialysis.
No specific dose adjustment for GFR >20 m L/min. For GFR 10-20 m L/min: use with caution, dose every 12-24 hours. For GFR <10 m L/min: not recommended due to lack of efficacy.
No dose adjustment required for mild to moderate hepatic impairment (Child-Pugh A or B); not studied in severe impairment (Child-Pugh C).
Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50%. Child-Pugh C: avoid use.
Safety and efficacy not established in pediatric patients.
IV/IM/PO: 0.015-0.1 mg/kg/dose every 6-24 hours; max 10 mg/day. For neonates: 0.01-0.05 mg/kg/dose every 12-24 hours.
No specific dose adjustment recommended; use caution due to potential for renal impairment, monitor renal function.
Start at 0.5 mg once daily; titrate cautiously due to increased sensitivity and risk of electrolyte imbalance and volume depletion.
Gastrointestinal perforation: Cases of gastrointestinal perforation have been reported in patients with conditions that may result in impaired structural integrity of the gastrointestinal tract.
Bumetanide is a potent diuretic that can lead to profound diuresis with water and electrolyte depletion. Close medical supervision and dose titration are required. Excessive doses can lead to hypovolemia, dehydration, and circulatory collapse.
Risk of gastrointestinal perforation,Opioid withdrawal symptoms including diarrhea, nausea, vomiting, abdominal pain,Disruption of analgesic effect if used with opioids crossing the blood-brain barrier (theoretical),Not recommended in patients with known or suspected mechanical gastrointestinal obstruction
Monitor fluid and electrolyte balance closely,Risk of ototoxicity, especially at high doses or with rapid infusion,May cause hyperuricemia and precipitate gout attacks,Can increase risk of digitalis toxicity due to hypokalemia
Known or suspected mechanical gastrointestinal obstruction,Known hypersensitivity to methylnaltrexone or any component of the formulation
Anuria,Severe electrolyte depletion,Hepatic coma or pre-coma,Hypersensitivity to bumetanide or sulfonamides
No specific food interactions reported with methylnaltrexone. No dietary restrictions necessary. However, to optimize bowel function, patients should maintain adequate fluid intake and dietary fiber as tolerated, unless contraindicated due to underlying illness.
No specific food restrictions, but limit salt intake to help control edema and hypertension. Avoid excessive intake of black licorice (can worsen hypokalemia). Grapefruit juice may not significantly interact, but caution with any electrolyte-altering foods. Maintain adequate fluid intake unless fluid restriction is advised by your doctor. Foods high in potassium (bananas, oranges, spinach) may be recommended if hypokalemia occurs; consult provider for individual needs.
Animal studies show no teratogenic effects at doses up to 300 mg/kg/day in rats and rabbits. No adequate human data; risk cannot be excluded in first trimester. Second and third trimester: limited data, potential for gastrointestinal effects in fetus if exposed transplacentally.
Bumetanide crosses the placenta. First trimester: No adequate human studies; animal studies show no teratogenicity at clinically relevant doses. Second and third trimesters: Risk of electrolyte imbalances and hypovolemia in the fetus; possible oligohydramnios. Avoid use during pregnancy unless benefits outweigh risks.
Excreted in human milk at low concentrations; M/P ratio approximately 0.6. No reported adverse effects in breastfeeding infants. Caution advised due to potential for gastrointestinal effects.
Bumetanide is excreted into human milk in small amounts (M/P ratio not determined). Due to potential for diuresis in the infant, use with caution, especially in neonates. Consider alternative agents with more safety data.
No pharmacokinetic studies in pregnancy; dose adjustments not recommended based on available data. Use only if clearly needed for severe opioid-induced constipation unresponsive to standard therapy.
Pregnancy may increase volume of distribution and renal clearance, potentially requiring higher doses. However, starting dose is generally unchanged; titration based on response and tolerability. Monitor for hypokalemia and hypovolemia.
Relistor (methylnaltrexone) is a peripherally acting mu-opioid receptor antagonist (PAMORA) used for opioid-induced constipation (OIC) in patients with advanced illness or chronic pain. It does not cross the blood-brain barrier, thus does not reverse central opioid analgesia. Administer subcutaneously; onset typically within 1-4 hours. Contraindicated in patients with known or suspected mechanical gastrointestinal obstruction. Use with caution in renal impairment (Cr Cl <30 m L/min) as dose reduction recommended. Monitor for gastrointestinal perforation, especially in patients with underlying GI pathology. Coadministration with other opioid antagonists may precipitate opioid withdrawal.
Bumetanide is a potent loop diuretic with rapid onset and short duration. Oral bioavailability is ~80% with minimal first-pass metabolism. Onset of diuresis within 30-60 minutes, peak at 1-2 hours, duration 4-6 hours. For acute pulmonary edema, intravenous bumetanide can be given 0.5-1 mg; onset within minutes. Monitor electrolytes especially potassium, magnesium, and calcium due to increased excretion. May cause ototoxicity, especially with rapid IV administration or concurrent aminoglycosides. Use with caution in sulfonamide allergy (cross-sensitivity). In renal impairment, bumetanide may be less effective due to reduced tubular secretion; higher doses may be needed. Combine with thiazides for sequential nephron blockade in resistant edema.
Relistor is used to treat constipation caused by opioid pain medications without affecting pain relief.,Inject the medication exactly as prescribed; do not use more often than every other day.,You should have a bowel movement within a few hours of receiving the injection; if not, contact your doctor.,Common side effects include abdominal pain, nausea, diarrhea, and flatulence.,Stop Relistor and seek immediate medical attention if you experience severe abdominal pain, vomiting, or signs of intestinal obstruction (e.g., inability to pass gas).,Tell your doctor if you have kidney problems, as the dose may need adjustment.,Do not take other medicines for constipation without your doctor's approval.
Take bumetanide exactly as prescribed, usually once daily in the morning to avoid nighttime urination.,Do not skip doses or double up on missed doses; if you miss a dose, take it as soon as you remember unless it is almost time for the next dose.,This medication can cause dehydration and electrolyte imbalances; notify your doctor if you experience excessive thirst, dry mouth, weakness, muscle cramps, or irregular heartbeat.,Avoid alcohol and over-the-counter medications, especially NSAIDs (ibuprofen, naproxen) unless approved by your doctor, as they may reduce bumetanide's effectiveness and increase kidney risk.,Stand up slowly from sitting or lying to prevent dizziness from low blood pressure.,Monitor your weight daily and report rapid weight gain or loss to your healthcare provider.
No interactions on record
"Concurrent use of bumetanide, a loop diuretic, and allopurinol, a xanthine oxidase inhibitor, may increase the risk of allopurinol hypersensitivity reactions, including Stevens-Johnson syndrome and acute gout flares. This interaction is thought to result from bumetanide-induced volume depletion and reduced renal clearance of oxypurinol, the active metabolite of allopurinol, leading to elevated serum oxypurinol levels and enhanced toxicity. Clinically, patients may present with rash, fever, eosinophilia, or acute gouty arthritis, particularly in those with renal impairment."
"Fenbufen, a nonsteroidal anti-inflammatory drug (NSAID), inhibits renal prostaglandin synthesis, which can reduce the efficacy of loop diuretics like bumetanide by blunting the diuretic-induced increase in renal blood flow and sodium excretion. This pharmacodynamic antagonism may result in diminished diuresis and natriuresis, potentially exacerbating fluid overload in patients with heart failure or hypertension. Clinically, this interaction may lead to suboptimal blood pressure control or worsening edema if the combination is used without dose adjustment."
"Concurrent administration of apomorphine, a dopamine agonist used for Parkinson's disease, with bumetanide, a loop diuretic, may lead to an increased risk of adverse effects, particularly hypotension and syncope. Apomorphine is known to cause orthostatic hypotension due to its vasodilatory and dopaminergic effects, which can be potentiated by bumetanide-induced volume depletion and electrolyte disturbances. This interaction can result in profound blood pressure drops, dizziness, and potential falls, especially in elderly patients or those with already compromised cardiovascular status."
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about RELISTOR vs BUMETANIDE, answered by our medical review team.
RELISTOR is a Peripheral Opioid Antagonist that works by Peripherally acting mu-opioid receptor antagonist that blocks opioid-induced constipation without affecting central analgesia.. BUMETANIDE is a Loop Diuretic that works by Inhibits the Na-K-2Cl symporter (NKCC2) in the thick ascending limb of the loop of Henle, reducing reabsorption of sodium, chloride, and potassium, leading to increased urine output.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between RELISTOR and BUMETANIDE depend on the specific clinical indication. These are agents from distinct pharmacological classes and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of RELISTOR is: 0.15 mg/kg subcutaneously once daily, maximum 16 mg per dose; for opioid-induced constipation, 8 mg subcutaneously once daily.. The standard adult dose of BUMETANIDE is: 0.5-2 mg IV/IM/PO once daily; may repeat every 6-8 hours; max 10 mg/day. Continuous IV infusion: 1 mg loading dose, then 0.5-2 mg/hour.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between RELISTOR and BUMETANIDE in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. RELISTOR is classified as Category C. Animal studies show no teratogenic effects at doses up to 300 mg/kg/day in rats and rabbits. No adequate human data; risk cannot be excluded in first trimester. Second and third tr. BUMETANIDE is classified as Category A/B. Bumetanide crosses the placenta. First trimester: No adequate human studies; animal studies show no teratogenicity at clinically relevant doses. Second and third trimesters: Risk o. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.