methylnaltrexone

Absorption: Rapidly absorbed after SUBQ and oral administration; oral absorption delayed by high-fat meal.

Distribution: Moderate tissue distribution, does not cross the blood-brain barrier.

Metabolism/Excretion: Some metabolism; 85% excreted unchanged in urine.

Half-Life: 15 hr (oral).

Time/Action Profile ⬆ ⬇

(plasma concentrations)

ROUTE	ONSET	PEAK	DURATION
SUBQ	rapid	0.5 hr	24–48 hr
PO	rapid	1.5 hr	unknown

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Known/suspected mechanical GI obstruction;
Lactation: Lactation.

Use Cautiously in:

Known/suspected lesions of GI tract (↑ risk for GI perforation);
Moderate or severe renal impairment (↓ dose);
Moderate or severe hepatic impairment (dose ↓ may be required);
OB: Use during pregnancy only if potential maternal benefit justifies potential fetal risk;
Pedi: Safety and effectiveness not established in children.

Adv. Reactions/Side Effects ⬆ ⬇

Derm: ↑sweating

GI: abdominal pain, flatulence, nausea, diarrhea

Neuro: dizziness

Misc: opioid withdrawal

Interactions ⬆ ⬇

Drug-drug:

None reported.

Route/Dosage ⬆ ⬇

Opioid-Induced Constipation in Patients With Advanced Illness

SC (Adults >114 kg): 0.15 mg/kg every other day, as needed (not to exceed one dose every 24 hr).

Renal Impairment

SC (Adults >114 kg): CCr <60 mL/min: 0.075 mg/kg every other day, as needed (not to exceed one dose every 24 hr).

Renal Impairment

SC (Adults 62–114 kg): CCr <60 mL/min: 6 mg every other day, as needed (not to exceed one dose every 24 hr).

Renal Impairment

SC (Adults 38–<62 kg): CCr <60 mL/min: 4 mg every other day, as needed (not to exceed one dose every 24 hr).

Renal Impairment

SC (Adults <38 kg): CCr <60 mL/min: 0.075 mg/kg every other day, as needed (not to exceed one dose every 24 hr).

Opioid-Induced Constipation in Patients With Noncancer Pain

SC (Adults ): 12 mg once daily.
PO (Adults ): 450 mg once daily.

Renal Impairment

SC (Adults ): CCr <60 mL/min: 6 mg once daily.

Renal Impairment

PO (Adults ): CCr <60 mL/min: 150 mg once daily.

Hepatic Impairment

SC (Adults >114 kg): Severe hepatic impairment: 0.075 mg/kg once daily.

Hepatic Impairment

SC (Adults 62–114 kg): Severe hepatic impairment: 6 mg once daily.

Hepatic Impairment

SC (Adults 38–<62 kg): Severe hepatic impairment: 4 mg once daily.

Hepatic Impairment

SC (Adults <38 kg): Severe hepatic impairment: 0.075 mg/kg once daily.

Hepatic Impairment

PO (Adults ): Moderate or severe hepatic impairment: 150 mg once daily.

Availability ⬆ ⬇

Tablets: 150 mg
Solution for injection (prefilled syringes): 8 mg/0.4 mL; 12 mg/0.6 mL
Solution for injection (single-use vials): 12 mg/0.6 mL

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.

Lab Test Considerations:

Monitor BUN, creatinine, sodium, potassium, and magnesium.
Monitor AST ALT, alkaline phosphatase, and bilirubin.

Implementation ⬆ ⬇

Maintenance laxative must be stopped before administration of methylnaltrexone. If response is not sufficient after 3 days, laxatives may be restarted.
PO: Administer with water on an empty stomach >30 min before 1st meal of the day.
SC: 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 one dose.

Patient/Family Teaching ⬆ ⬇

Explain purpose and side effects of medication to patient. Advise patient to read Patient Information before starting therapy. Instruct patient to take as directed and teach appropriate injection technique and syringe/needle disposal. Usual schedule is one dose every other day, as needed, but no more than one dose in a 24-hr period.
Advise patient to notify health care provider of all Rx or OTC medications, vitamins, or herbal products being taken and to consult health care provider before taking other medications.
Advise patient that laxation may occur within 30 min of SUBQ injection; toilet facilities should be available following administration.
Advise patient to discontinue all maintenance laxatives; can be added if inadequate response to methylnaltrexone.
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 provider 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.
Rep: Advise women of reproductive potential to notify health care provider if pregnancy is planned or suspected or if breastfeeding.

section name header

Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

Action ⬆ ⬇

Pharmacokinetics ⬆ ⬇

Time/Action Profile ⬆ ⬇

Contraind./Precautions ⬆ ⬇

Adv. Reactions/Side Effects ⬆ ⬇

Interactions ⬆ ⬇

Route/Dosage ⬆ ⬇

Availability ⬆ ⬇

Assessment ⬆ ⬇

Implementation ⬆ ⬇

Patient/Family Teaching ⬆ ⬇

Evaluation/Desired Outcomes ⬆ ⬇

US Brand Names ⬆