Withdrawn [This study was terminated early by Wyeth, prior to dosing any subjects, for business reasons not related to safety.](streamdown:incomplete-link)

This purpose of this study is to evaluate the safety and effectiveness of a subcutaneous (injection beneath the skin) form of methylnaltrexone in subjects who have cancer-related pain and constipation from taking opioids. The length of participation will be up to 7 weeks.

Inclusion Criteria:

• Is a man or woman aged 18 years or older.
• Has a body weight >= 38 kg.
• Has cancer (active or in remission), and has cancer-related pain (ie, pain due to cancer or treatment of cancer).
• Has a life expectancy of >= 6 months.
• Has a performance status of 0, 1, or 2 based on the Eastern Cooperative Oncology Group (ECOG) scale.
• Is taking opioids for cancer-related pain, and not just as-needed doses.
• Has a diagnosis of OIC as determined by the investigator.
• Is willing to follow the protocol instructions on laxative use during the study.

Exclusion Criteria:

• Has a history of chronic constipation before starting opioids.
• Has renal disease receiving dialysis.
• Has an ostomy for stools.
• Is a pregnant or breastfeeding woman.