By Bruce Sylvester
SAN DIEGO -- October 27, 2009 -- Patients with chronic nonmalignant pain experiencing opioid-induced constipation show significant improvements following treatment with subcutaneous (SC) methylnaltrexone, researchers stated here at the American College of Gastroenterology (ACG) 74th Annual Scientific Meeting.
"Subcutaneous methylnaltrexone appears to be a highly-effective treatment for opioid-induced constipation," said presenter and investigator Evan Tzanis, Wyeth Research, Collegeville, Pennsylvania, on October 25.
For the study, researchers randomised 469 patients (460 evaluable) to receive either daily methylnaltrexone SC (n = 150), every-other-day dosing (n = 148), or placebo (n = 162) for 4 weeks.
Eligibility for the study included opioid dosing of >=50 mg oral morphine equivalents per day for >=2 weeks and <3 rescue-free bowel movements per week. Back pain (60%) was the most frequently reported pain condition.
Potential patients with significant gastrointestinal or other medical disorders were excluded, as were those with a history of chronic constipation prior to opioid use or a history of alcohol or drug abuse within 1 year of screening.
The researchers assessed symptoms using the Patient Assessment of Constipation-Symptoms (PAC-SYM) questionnaire at day 14 and day 28. They used standard statistical analyses to compare methylnaltrexone and placebo data.
Results showed that at day 28, patients in the daily dosing group had achieved significant improvement compared with placebo for rectal symptoms (-0.56 vs -0.30; P < .05), stool symptoms (-0.76 vs -0.43; P < .001), and the global PAC-SYM scores (-0.62 vs -0.37; P < .001).
Subjects in the every-other-day dosing group achieved significant improvement in stool symptoms (-0.69 vs -0.43; P < .05) and the global PAC-SYM scores (-0.52 vs -0.37; P < .05) compared with placebo.
No significant differences appeared in abdominal symptom scores between either the once-daily group and placebo or the every other day group and placebo.
Funding for this study was provided by Wyeth Research.
[Presentation title: Effect of Methylnaltrexone SC on Constipation Symptoms Using the Patient Assessment of Constipation Symptoms (PAC-SYM) Questionnaire in Patients with Chronic Non-Malignant Pain and Opioid-Induced Constipation. Abstract 274]
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