methylnaltrexone bromide

Action

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

Availability

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)

Contraindications

• Known or suspected mechanical GI obstruction

Precautions

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).

Administration

• 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

Interactions

None

Patient monitoring

See 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.

See 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.