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
• 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.
CNS: dizziness, malaise
GI: nausea, abdominal pain, diarrhea, flatulence abdominal cramping, GI perforation
Other: flushing, pain, diaphoresis
☞ Monitor patient for severe or persistent diarrhea and signs and symptoms of GI perforation. Discontinue drug if either occurs.
• 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.
Pharmacologic: opioid antagonists
|Subcut||rapid||0.5 hr||24–48 hr|
Adverse Reactions/Side Effects
Central nervous system
- GI perforation (life-threatening)
- abdominal pain (most frequent)
- flatulence (most frequent)
- nausea (most frequent)
Drug-Drug interactionNone noted.
Renal Impairment(Adults) CCr <30 mL/min—use 50% of recommended dose based on weight.
- 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 DiagnosesConstipation (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.
- 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.
- Laxation and relief of opioid-induced constipation.
RelistorA 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.
Abdominal pain, flatulence.