Webster LR, et al. - In this Phase III, randomized, double-blind, placebo-controlled trial, researchers analyzed the effect of oral methylnaltrexone, a peripherally acting µ-opioid receptor antagonist, on opioid analgesia in adults with chronic noncancer pain. They administered oral methylnaltrexone 150 mg/day (n=201), 300 mg/day (n=201), 450 mg/day (n=200), or placebo (n=201) once daily for 4 weeks, followed by 8 weeks of oral methylnaltrexone as needed, in patients taking ≥50 mg/day oral morphine equivalent dose (MED) for ≥14 days before screening with less than three rescue-free bowel movements/week. They found that oral methylnaltrexone neither elicited opioid withdrawal nor it interfered with opioid analgesia.