What is "alvimopan"

n. (context pharmaceutical drug English) A particular narcotic painkiller.

Alvimopan (trade name Entereg) is a drug which behaves as a peripherally acting μ-opioid antagonist. With limited ability to cross the blood–brain barrier, many of the undesirable side-effects of the opioid agonists such as constipation are minimized without affecting analgesia or precipitating withdrawal. It is currently only Food and Drug Administration approved for the treatment of postoperative ileus which it received in May 2008.