FDA approves Relistor (methylnaltrexone bromide) for Opioid-Induced Constipation

On April 28, 2008, the Food and Drug Administration (FDA) approved a new drug to restore bowel function in patients who receive opioids long-term for pain management.  Opioids are often prescribed continuously for patients with advanced illness, such as incurable cancer, HIV/AIDS, COPD, and heart failure.  Opioids relax the intestinal smooth muscles, preventing them from contracting properly and therefore hindering normal bowel elimination.  Patients often suffer from constipation and painful elimination.  Relistor acts to block opioid entrance into the intestinal cells, allowing the bowel to function normally despite the use of opioids. 

Relistor is indicated for treatment of constipation in patients with advanced illness receiving palliative care after failing laxative therapy.  The injectable drug is dosed once every other day as needed with a maximum of one dose every 24 hours.  Side effects include abdominal pain, gas, nausea, dizziness, and diarrhea.  Relistor is not recommended for patients with known or suspected intestinal obstructions.
Two randomized, double-blind placebo-controlled studies included a total of 287 patients and were conducted over a four-month period.  Inclusion criteria included late-stage illness, life expectancy of less than 6 months, and fewer than three bowel movements in the week prior to treatment or no bowel movement for more than 2 days.  The patients receiving Relistor had a significantly higher rate of elimination than those patients receiving placebo.  Relistor is manufactured by Wyeth Pharmaceuticals and Progenics Pharmaceuticals. 

References:

1. FDA Press Release, April 28, 2008.
2. Relistor.  In: DRUGDEX System [Internet database].  Greenwood Village, Colo: Thomson Micromedex.  Updated periodically.  Accessed May 7, 2008.

Keri Del Signore, Doctor of Pharmacy Candidate