Methylnaltrexone is a special narcotic drug that blocks certain effects of other narcotic medicines. Methylnaltrexone reduces constipation caused by narcotic medications that are often used to treat pain in people with terminal illness. Methylnaltrexone works by preventing this side effect without reducing the pain-relieving effects of the narcotic. Methylnaltrexone is usually given after laxatives have been tried without successful treatment of constipation. Methylnaltrexone may also be used for purposes not listed in this medication guide.
Relistor is used to treat constipation, which is caused by the opioid pain medications in patients. It is given in the form of injection. It protects the bowel from the effects of Narcotic (opioid) medications. Relistor is also used to treat the effect of the drug such as the precipitating withdrawals.