Study SB-767905/008 was a multicenter study to evaluate the effectiveness and safety of multiple dosage regimens of an investigational drug for the treatment of constipation due to prescription pain medication in participants with cancer pain.

Study ABD101684 will serve as an extension to Study SB-767905/008 and offer continued access to blinded investigational product to participants who have completed the original study. The purpose of Study ABD101684 is to evaluate the safety and efficacy of alvimopan compared to placebo in subjects who completed Study SB-767905/008 and elected to participate in this extension study.

Inclusion Criteria:

• Completed GSK sponsored alvimopan (opioid-induced bowel dysfunction) OBD study for subjects with cancer-related pain, e.g. SB-767905/008.
• Taking full agonist opioid therapy for cancer related pain.
• Met entry criteria of OBD in original study and per investigator continues to require therapy for management of OBD.
• Capable of completing paper questionnaires at the study visits.

Exclusion Criteria:

• Unable to eat or drink.
• Taking opioids for management of drug addiction.
• Unable to use only rescue laxatives provided.
• Inappropriately managed severe constipation that puts subject at risk of complications.
• Has gastrointestinal (GI) or pelvic disorder known to affect bowel transit.
• Concomitant medication(s), medical condition, or clinically significant laboratory abnormality that could jeopardize subject and also contraindicate study participation.