(redirected from Methylnaltrexone Br)

methylnaltrexone bromide


Pharmacologic class: Mu-opioid receptor antagonist (peripherally acting)

Therapeutic class: Opioid

Pregnancy risk category B


Selectively antagonizes opioid binding at mu-opioid receptors (such as those in GI tract) while having restricted ability to cross blood-brain barrier, thereby decreasing constipating effects of opioids without altering analgesic effects on CNS


Solution for injection: 12 mg/0.6 ml in single-use vials

Indications and dosages

Opioid-induced constipation in patients with advanced illness who are receiving palliative care and haven't responded adequately to laxatives

Adults weighing 62 to less than 114 kg (136 to less than 251 lb): 12 mg subcutaneously every other day as needed, but no more frequently than one dose in 24 hours

Adults weighing 38 to less than 62 kg (84 to less than 136 lb): 8 mg subcutaneously every other day as needed, but no more frequently than one dose in 24 hours

Adults weighing outside above ranges: 0.15 mg/kg subcutaneously every other day as needed, but no more frequently than one dose in 24 hours

Dosage adjustment

• Severe renal impairment (creatinine clearance less than 30 ml/minute)


• Known or suspected mechanical GI obstruction


Use cautiously in:

• renal impairment

• severe or persistent diarrhea, known or suspected GI tract lesions

• pregnant or breastfeeding patients

• children (safety and efficacy not established).


• Once drawn into syringe, if drug won't be given immediately, store at ambient room temperature and administer within 24 hours.

Adverse reactions

CNS: dizziness, malaise

GI: nausea, abdominal pain, diarrhea, flatulence abdominal cramping, GI perforation

Other: flushing, pain, diaphoresis



Patient monitoring

Monitor patient for severe or persistent diarrhea and signs and symptoms of GI perforation. Discontinue drug if either occurs.

Patient teaching

• Teach patient who will take drug at home how to prepare and administer it and discard supplies properly.

• Tell patient that if drug won't be administered immediately after it's drawn into syringe, it should be stored at ambient room temperature and administered within 24 hours.

• Inform patient that solution should be clear and colorless to pale yellow.

• Advise patient to stay near toilet facilities after receiving drug.

Instruct patient to stop taking drug if severe or persistent diarrhea or severe, persistent, or worsening abdominal signs or symptoms occur.

• Tell patient that common side effects include transient abdominal pain, nausea, and vomiting. Advise patient to contact prescriber if these symptoms persist or worsen.

• Instruct patient to stop taking drug if opioid pain medication is discontinued.

• As appropriate, review all other significant adverse reactions mentioned above.

McGraw-Hill Nurse's Drug Handbook, 7th Ed. Copyright © 2013 by The McGraw-Hill Companies, Inc. All rights reserved


(me-thil-nal-trex-one) ,


(trade name)


Therapeutic: laxatives
Pharmacologic: opioid antagonists
Pregnancy Category: B


Treatment of constipation caused by opioid use in patients being treated palliatively, when laxative therapy has failed.


Acts peripherally as mu-opioid receptor antagonist, blocking opioid effects on the GI tract.

Therapeutic effects

Blocks constipating effects of opioids on the GI tract without loss of analgesia.


Absorption: Rapidly absorbed after subcutaneous administration.
Distribution: Moderate tissue distribution, does not cross the blood-brain barrier.
Metabolism and Excretion: Some metabolism; 85% excreted unchanged in urine.
Half-life: 8 hr.

Time/action profile

Subcutrapid0.5 hr24–48 hr


Contraindicated in: Known/suspected mechanical GI obstruction.
Use Cautiously in: Known/suspected lesions of GI tract (↑ risk for GI perforation); Obstetric / Lactation: Use in pregnancy only if clearly needed; use cautiously during lactation; Pediatric: Safety and efficacy not established.

Adverse Reactions/Side Effects

Central nervous system

  • dizziness


  • GI perforation (life-threatening)
  • abdominal pain (most frequent)
  • flatulence (most frequent)
  • nausea (most frequent)
  • diarrhea


  • hyperhidrosis


Drug-Drug interaction

None noted.


Subcutaneous (Adults) 38–<62 kg—8 mg every other day, not to exceed every 24 hr; 62–114 kg—12 mg every other day, not to exceed every 24 hr; other weights—0.15 mg/kg every other day, not to exceed every 24 hr.

Renal Impairment

(Adults) CCr <30 mL/min—use 50% of recommended dose based on weight.


Solution for subcutaneous injection (single use vial): 12 mg/0.6 mL Cost: $500.22 / 7 vials
Solution for subcutaneous injection (prefilled syringes): 8 mg/0.4 mL, 12 mg/0.6 mL Cost: All strengths $71.46 / syringe

Nursing implications

Nursing assessment

  • Assess bowel sounds and frequency, quantity, and consistency of stools periodically during therapy.
  • Monitor pain intensity during therapy. Methylnaltrexone does not affect pain or effects of opioid analgesics on pain control.

Potential Nursing Diagnoses

Constipation (Indications)
Diarrhea (Adverse Reactions)


  • Subcutaneous: Pinch skin and administer in upper arm, abdomen, or thigh at a 45° angle using a 1-mL syringe with a 27-gauge needle inserted the full length of the needle. Do not rub the injection site. Solution is clear and colorless to pale yellow. Do not administer solutions that are discolored or contain a precipitate. Solution is stable for 24 hr at room temperature. Protect vials from light. Do not freeze. Do not use single-use vials for more than 1 dose.

Patient/Family Teaching

  • Instruct patient on administration of methylnaltrexone and disposal of supplies. Usual schedule is one dose every other day, as needed, but no more than one dose in a 24-hr period. Advise patient to read the Patient Information prior to starting therapy and with each Rx refill.
  • Advise patient that laxation may occur within 30 min, so toilet facilities should be available following administration.
  • Advise patient to continue taking other medications for constipation unless told not to by health care professional.
  • May cause dizziness. Caution patient to avoid driving and other activities requiring alertness until response to medication is known.
  • Advise patient to notify health care professional and discontinue therapy if severe or persistent diarrhea occurs or if abdominal pain, nausea, or vomiting persists or worsens.
  • Instruct patient to stop taking methylnaltrexone if they stop taking opioid medications.
  • Advise patient to consult health care professional prior to taking other Rx, OTC, or herbal products.
  • Advise female patients to notify health care professional if pregnancy is planned or suspected or if breast feeding.

Evaluation/Desired Outcomes

  • Laxation and relief of opioid-induced constipation.
Drug Guide, © 2015 Farlex and Partners


A proprietary quaternary amine and mu opioid receptor antagonist, which reverses opioid-induced constipation, without impacting on central opioid analgesia.

Patients receiving palliative care for whom usual laxatives have failed.

Adverse effect
Abdominal pain, flatulence.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.