Adults who are taking opioid therapy for persistent non-cancer pain and have resulting opioid-induced bowel dysfunction (OBD) will be randomized (1:1:1) to one 2 alvimopan arms, or to placebo. The primary objective of this phase 3 confirmatory study is to compare alvimopan with placebo for efficacy in the treatment of OBD. The primary efficacy endpoint is based on frequency of bowel movements. Subjects will be required to: (1) track their bowel movements and other bowel symptoms and (2) attend 6 clinic visits over 4 months.