Naloxone treatment for irritable bowel syndrome - a randomized controlled trial with an oral formulation

Background: Opioids change gut motility and secretion, causing delayed intestinal transit and constipation. Endorphins play a role in the constipation troubling some patients with irritable bowel syndrome; hence naloxone, an opioid antagonist, may have a therapeutic role. Aim: To assess the efficacy and safety of an oral formulation of naloxone in irritable bowel syndrome patients with constipation. Methods: A randomized, double-blind, placebo-controlled trial was performed. Patients fulfilling the Rome II criteria for irritable bowel syndrome (constipation-predominant and alternating types) were randomized to receive 8 weeks of treatment with naloxone capsules, 10 mg twice daily, or identical placebo. Results: Twenty-eight patients entered the study, which was completed by 25. 'Adequate symptomatic relief' was recorded in six of 14 on naloxone and three of 11 on placebo. Whilst the differences were not significant, improvements in severity gradings and mean symptom scores for pain, bloating, straining and urgency to defecate were greater with naloxone than placebo for all parameters. In addition, quality of life assessments improved to a greater extent in patients taking naloxone. Conclusions: Preliminary results suggest that naloxone is well tolerated and beneficial in patients with irritable bowel syndrome and constipation. A larger clinical trial is needed to provide sufficient statistical power to assess efficacy.