The Pharmaceutical Journal
Vol 276 No 7401 p586
20 May 2006

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New approach to constipation

Alvimopan (Entereg), a new class of peripheral opioid receptor antagonist — designed for treating the gastrointestinal symptoms associated with opioids — doubled spontaneous bowel movements in a study of 522 patients, according to data presented at the American Pain Society annual scientific meeting in San Antonio, Texas, this month.

Alvimopan, unlike the antagonist naloxone, does not cross the blood-brain barrier, and hence does not limit analgesia.

In the phase IIb study, patients were taking opioids for persistent non-cancer pain. Those treated with alvimopan 0.5mg twice daily showed an average weekly increase in spontaneous bowel movements of 3.58 over six weeks (P<0.001). Subjects receiving alvimopan 1mg once daily had an increase of 3.39 and those treated with alvimopan 1mg twice daily showed a weekly increase of 4.34 (P<0.001 for each). Patients given placebo had a weekly increase of 1.71.

Principal investigator Lynn Webster, from Lifetree Clinical Research and Pain Clinic, Salt Lake City, Utah, commented that alvimopan would allow patients with a tendency to constipation to receive higher doses of narcotics.