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| |  Methylnaltrexone Relieves Opioid-Induced Constipation in Patients With Noncancer Pain: Presented at APS By Ed Susman SAN DIEGO -- May 13, 2009 -- Constipation induced by opioid use can be relieved rapidly with subcutaneous injections of methylnaltrexone compared with placebo, researchers stated here at the 28th Annual Scientific Meeting of the American Pain Society (APS). "As many as 40% of people who are taking opioids for pain relief experience constipation that is severe enough to cause major limitations to their quality of life," said E. Richard Blonsky, MD, Pain and Rehabilitation Clinic, and Northwestern University's Feinberg School of Medicine, Chicago, Illinois. "Opioid analgesics are often used to treat chronic, nonmalignant pain, such as osteoarthritis, back pain, and neuropathic pain," Dr. Blonsky said at his poster presentation on May 8. "Methylnaltrexone, a selective peripherally active mu-opioid receptor antagonist, decreases the constipating effects of opioids without affecting centrally mediated analgesia." Dr. Blonsky and colleagues enrolled 460 patients in a randomised, double-blind, placebo-controlled, phase 3 study designed to determine if methylnaltrexone can relieve opioid-induced constipation. He said the goal of treatment is to free patients from being tied to their homes, never certain when the urge to void would occur due to unpredictable nature of constipation and of common laxatives. With methylnaltrexone, he said, the patient could predict that bowel movements would occur within 4 hours of delivery of the subcutaneous injection. They found that 34.3% of patients accomplished laxation within 4 hours of taking the injection compared with 9.9% of patients on placebo (P < .001). Among the 150 patients taking methylnaltrexone every day, 28.9% achieved laxation within 4 hours, compared with 9.4% of the 162 patients on placebo (P < .001); and 30.2% of 148 patients taking methylnaltrexone every other day achieved laxation within 4 hours (P < .001). While patients assigned to methylnaltrexone complained more often about abdominal pain, Dr. Blonsky noted that 81.2% of patients who were assigned to the active treatment completed the trial, and just 7.75% of those who withdrew did so due to adverse events. "These results suggest that subcutaneous methylnaltrexone is an effective and generally well-tolerated treatment for opioid-induced constipation in patients with chronic nonmalignant pain," Dr. Blonsky concluded. Funding for this study was provided by Wyeth Research. [Presentation title: Subcutaneous Methylnaltrexone for the Treatment of Opioid-Induced Constipation in Patients With Chronic Non-Malignant Pain. Abstract 351]
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