Background and Objectives In patients with chronic noncancer pain, subcutaneous methylnaltrexone for opioid-induced constipation (OIC) was examined in a randomized controlled trial (RCT) followed by an open-label extension (OLE). This study examined the reproducibility of RCT findings by analyzing data from placebo-treated patients who crossed over to methylnaltrexone.
Methods Adults with less than 3 weekly rescue-free bowel movements (RFBMs), taking 50 mg or more of an oral morphine equivalent per day, were randomized to receive methylnaltrexone 12 mg or placebo for 4 weeks, followed by open-label methylnaltrexone 12 mg as needed for 8 weeks.
Results A total of 134 placebo-treated patients (median morphine equivalent dose, 150 mg/d; mean of 1.1 RFBM per week) crossed over to methylnaltrexone in OLE. During the RCT, 9.7% of placebo-treated patients experienced an RFBM within 4 hours of first dose and 9.0% of all placebo injections resulted in an RFBM within 4 hours compared with 45.9% and 34.5%, respectively, with methylnaltrexone treatment in the OLE. When expressed as percentage of patients experiencing 3 or more RFBMs per week and a 1-RFBM increase over baseline, weekly values ranged from 35% to 40% during placebo treatment; at week 5 of OLE methylnaltrexone, this percentage increased to more than 70% and remained relatively stable throughout the OLE. The most common adverse events during methylnaltrexone treatment were abdominal pain (9.7% vs 1.5% for placebo) and nausea (5.2% vs 6.7%).
Conclusions Findings during placebo treatment further establish the profile of OIC and support that little or no gastrointestinal tolerance develops across time. Findings under open-label conditions established the reproducibility and durability of methylnaltrexone for OIC.
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Dr Viscusi has received honoraria and consulting fees from Salix, a division of Valeant Pharmaceuticals North America LLC, Bridgewater, NJ.
The other authors are former employees of Salix.
Funding was received from Salix, a Division of Valeant Pharmaceuticals North America LLC, Bridgewater, NJ.
Presented in part at the 13th Annual Pain Medicine Meeting of the American Society of Regional Anesthesia and Pain Medicine, November 13–16, 2014, San Francisco, CA.
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