Pathogenesis, Updates on Current Treatment Options and Alvimopan for Postoperative Ileus

ABSTRACT: Postoperative Ileus (POI) is a recurrent incident following intestinal as well as other types of surgery that causes aggregation of gases and inner secretions in patients, resulting in significant costs to health care providers and morbidity. The pathophysiology of the POI is multifactorial, and treatment duration of the POI associated with the degree of surgical trauma. Exogenous opioids, neurohormonal dysfunction, fluid overload, inflammation, and gastrointestinal strain are the main pathophysiological factors underlying POI. Different treatment options currently available to reduce duration of POI. Recent studies have shown that the effective approaches in reducing patient morbidity with early return of gut functions are Enhanced Recovery After Surgery (ERAS) pathway and laparoscopic surgery. Alvimopan (ALV) is a peripherally acting antagonist of the µ opioid receptor in postoperative ileus. Alvimopan (Entereg®), the FDA-approved product for the fastest recovery of bowel (large and small) resection with primary anastomosis, shows potential advances for the treatment of POI. It has limited bioavailability through the oral route due to solubility limitations. ALV prevents binding of opioid agonists to the μ-opioid receptor and assists in stopping constipation in the GI tract; it is also not able to cross the blood-brain barrier, so it does not obstruct with centrally mediated opioid analgesia. The safety & efficacy studies of Alvimopan showed that the patients who go through segmental bowel surgeries along with primary anastomosis and given ALV reduces the duration of stay and overall direct costs compared with control group. The objectives of this systematic review were to give an update of categorization systems, pathogenesis mechanisms, current treatment for established POI, and updates on Alvimopan for POI.