• Gordon Irving, Janos Pénzes, Brian Ramjattan, Michael Cousins, Richard Rauck, Egilius L H Spierings, Christi S Kleoudis, Jerry W Snidow, Amy Pierce, John Wurzelmann, and Eric R Mortensen.
• Swedish Medical Center, Seattle, Washington 98104, USA. gordon.irving@swedish.org
• J Pain. 2011 Feb 1;12(2):175-84.

UnlabelledThe balance between the pain relief provided by opioid analgesics and the side effects caused by such agents is of particular significance to patients who take opioids for the long-term relief of non-cancer pain. The spectrum of signs and symptoms affecting the gastrointestinal (GI) tract associated with opioid use is known as opioid-induced bowel dysfunction. Alvimopan is an orally administered, systemically available, peripherally acting mu-opioid receptor (PAM-OR) antagonist, approved in the US for the management of postoperative ileus in patients undergoing bowel resection (short-term, in-hospital use only). Alvimopan was under clinical development for long-term treatment of opioid-induced constipation (OIC) but this program has been discontinued. This double-blind, placebo-controlled trial, part of the former OIC development program, enrolled patients (N = 485) receiving opioids for non-cancer pain. Patients were randomized to receive alvimopan .5 mg once daily, alvimopan .5 mg twice daily, or placebo, for 12 weeks. The primary efficacy endpoint was the proportion of patients who experienced ≥ 3 spontaneous bowel movements (SBMs; bowel movements with no laxative use in the previous 24 hours) per week over the treatment period, and an average increase from baseline of ≥ 1 SBM per week. There were greater proportions of SBM responders in both alvimopan treatment groups (63% in both groups) compared with placebo (56%), although these differences were not statistically significant. Secondary efficacy analyses indicated that alvimopan was numerically superior to placebo in improving opioid-induced bowel dysfunction symptoms and patients' global assessment of opioid-induced bowel dysfunction, and reduced the requirement for rescue laxatives. Active treatment was well tolerated and alvimopan did not antagonize opioid analgesia.PerspectiveAlthough the primary endpoint was not met in this study, the magnitude of alvimopan-induced improvements versus baseline, together with previous study results, suggest that a PAM-OR antagonist has the potential to improve OIC.Copyright © 2011 American Pain Society. Published by Elsevier Inc. All rights reserved.

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