Subject registration did not proceed as expected; difficult to complete within scheduled time frame; prematurely terminated w/ 21 subjects randomized.

This study is intended to investigate the recommended dose of alvimopan in doses 0.25mg/day (0.25mg, OD), 0.5mg/day (0.25mg, BID) or 1mg/day (0.5mg, BID) or placebo for 3 weeks in patients who receive opioids for the management of cancer pain and develop constipation, by giving overall consideration to the efficacy and safety data in each treatment group. Also, efficacy and safety data of alvimopan in the recommended dose group will be compared with those of placebo and to confirm alvimopan's safety and efficacy.

Inclusion criteria:

• Have cancer.
• Taking opioid therapy for continued intractable pain.
• Experiencing less bowel movement frequency compared to that before the opioid treatment.
• Must meet the protocol-definition of opioid-induced constipation.

Exclusion criteria:

• Gastrointestinal or pelvic disorders known to affect gastrointestinal functions or induce bowel transit disorder and ileus.
• Subjects, who in the investigator's opinion, have gastrointestinal dysfunction predominantly due to causes other than the use of opioids.