Methylnaltrexone Bromide

Peripherally acting μ-opiate receptor antagonist;1 2 3 4 7 8 9 12 13 quaternary amine derivative of naltrexone.4 7 9 11 13

Absorption

Bioavailability

Rapidly absorbed following sub-Q administration.1

Onset

Laxation within 30 minutes in about 30% of patients; within 4 hours in about 50–60% of patients.1

Distribution

Extent

Moderate tissue distribution.1

Distributed into milk in rats; not known whether distributed into human milk.1

Plasma Protein Binding

11–15%.1 13

Elimination

Metabolism

Metabolized to several minor metabolites.1 Not appreciably demethylated to form naltrexone.1 4 13

Elimination Route

Excreted principally as unchanged drug in urine (50%) and in feces.1 13

Half-life

Approximately 8 hours.1

Special Populations

Mild or moderate hepatic impairment does not affect systemic exposure; not studied in patients with severe hepatic impairment.1 10

Severe renal impairment (Clcr <30 mL/minute) decreases renal clearance 8- to 9-fold and doubles AUC.1 (See Renal Impairment under Dosage and Administration.)

Not studied in patients with end-stage renal disease requiring dialysis.1 10

Methylnaltrexone bromide is used to treat constipation caused by opioids (narcotic pain medicines), in adults with long-lasting pain that is not caused by cancer. methylnaltrexone bromide is used when other medicines for constipation (laxatives) have not worked well.

methylnaltrexone bromide is available only with your doctor's prescription.

It is very important that your doctor check your progress at regular visits. This will allow your doctor to see if the medicine is working properly and to decide if you should continue to use it.

methylnaltrexone bromide may cause a tear (perforation) in your stomach or bowels. Check with your doctor right away if you have a severe stomach pain that does not go away.

If severe or persistent (non-stop) diarrhea occurs while using methylnaltrexone bromide, check with your doctor right away.

Do not suddenly stop using methylnaltrexone bromide without checking first with your doctor. Doing so may cause symptoms, such as anxiety, chills, diarrhea, irritability, stomach pain, sweating, and yawning.