The FDA has accepted for review the NDA submitted by Adolor and GlaxoSmithKline for alvimopan (Entereg) for the management of postoperative ileus (POI). Alvimopan is the first of a new class of drugs known as peripherally acting mu opioid receptor antagonists. After it is administered orally, its activity is specific to the gastrointestinal tract. Many patients undergoing abdominal surgery experience transient GI impairment (abdominal distention and pain, nausea and vomiting, lack of appetite, inability to pass gas or stool), a condition known as POI. Postoperative recovery of GI function and resumption of oral intake are critical determinants of the length of hospital stay.