Opioid-induced bowel dysfunction: pathophysiology and potential new therapies.

Area of Science:

• Gastroenterology
• Pharmacology
• Pain Management

Background:

• Opioid analgesics, while effective for pain, commonly cause debilitating bowel dysfunction.
• Opioid-induced bowel dysfunction involves complex gastrointestinal effects, including reduced motility and increased fluid absorption.
• Current management strategies for opioid-induced bowel dysfunction are often nonspecific and ameliorative.

Purpose of the Study:

• To investigate the efficacy of peripherally acting opioid antagonists in managing opioid-induced bowel dysfunction.
• To evaluate whether these antagonists can reverse gastrointestinal side effects without compromising central analgesic effects.

Main Methods:

• Review of investigations into opioid receptor classes (mu, delta, kappa) and their roles in central and peripheral actions.
• Analysis of clinical studies on novel opioid antagonists, methylnaltrexone and alvimopan, focusing on their peripheral receptor activity.
• Examination of recent clinical data on alvimopan's effect on postoperative ileus and chronic pain-related bowel dysfunction.

Main Results:

• Activation of peripheral mu-opioid receptors in the gut inhibits motility, contributing to opioid-induced bowel dysfunction.
• New antagonists, methylnaltrexone and alvimopan, target peripheral opioid receptors, reversing bowel dysfunction without central effects.
• Alvimopan has demonstrated the ability to normalize bowel function in surgical and non-surgical patients on opioids, without reversing analgesia.

Conclusions:

• Blocking peripheral opioid receptors is a logical therapeutic strategy for opioid-induced bowel dysfunction.
• Peripherally restricted opioid antagonists offer a promising approach to manage opioid-induced bowel dysfunction.
• Alvimopan shows potential for normalizing bowel function in both chronic pain and postoperative settings without compromising pain relief.