Alvimopan, a trans-3,4-dimethyl-4-(3-hydroxy-phenyl) piperidine, is a selective, peripherally acting micro-opioid receptor antagonist that is available for short-term use in hospitalized patients who have undergone bowel resection. The efficacy of alvimopan in the management of postoperative ileus has been evaluated in five phase III trials; four conducted in North America and one conducted in Europe/Australasia. Patients who had undergone partial large or small bowel resection surgery with primary anastomosis were randomized to receive alvimopan 12 mg or placebo as a single oral pre-operative dose followed by twice-daily administration for up to 7 days postoperatively. In the five phase III trials, alvimopan was significantly more effective than placebo in reducing the time to recovery of upper and lower gastrointestinal (GI) function, as assessed using a two-component endpoint (GI2) comprising time to tolerance of solid food and first bowel movement. The mean time to reach the GI2 endpoint was 11-26 hours sooner with alvimopan than with placebo. In the phase III trials conducted in North America, the time to writing the hospital discharge order was 13-21 hours sooner with alvimopan than with placebo. Alvimopan did not reduce opioid-induced analgesia and/or increase the amount of opioids administered postoperatively. Short-term alvimopan was generally well tolerated in adults undergoing bowel resection.