Study Evaluating Subcutaneous Methylnaltrexone For Treatment Of Opioid-Induced Constipation In Patients With Advanced Illness

Inclusion Criteria: * Is an adult 18 years of age or older * Has a diagnosis of advanced illness (ie, a terminal illness such as incurable cancer or other end-stage disease) * Has a life expectancy of at least 1 month. * Is receiving opioids on a regular schedule (not just as-needed or rescue doses) for the control of pain or discomfort for at least 2 weeks before the first dose of study drug. * Has constipation that is caused by opioid medications. Exclusion Criteria: * Has a known or suspected allergy to methylnaltrexone or other similar compounds (e.g. naltrexone or naloxone). * Has a known or suspected mechanical gastrointestinal obstruction. * Has any potential nonopioid cause of bowel dysfunction that might be a major contributor to the constipation. * Has any other clinically important abnormalities as determined by the investigator that may interfere with his or her participation in or compliance with the study. * Receiving opioid antagonist or partial antagonist products.