The team assessed the efficacy and safety of an oral formulation of naloxone in irritable bowel syndrome (IBS) patients with constipation.
The findings of the study were published in the September issue of Alimentary Pharmacology & Therapeutics.
Opioids change gut motility and secretion, causing delayed intestinal transit and constipation.
Endorphins play a role in the constipation troubling some patients with IBS.
Hence the authors hypothesized that naloxone, an opioid antagonist, may have a therapeutic role in IBS.
Some 28 patients entered the randomized, double-blind, placebo-controlled trial, and 25 completed it.
All patients fulfilled the Rome II criteria for IBS (constipation-predominant and alternating types).
- Urgency to defecate
| Alimentary Pharmacology & Therapeutics |
They were then randomized to receive 8-weeks of treatment with naloxone capsules, 10mg twice daily, or identical placebo.
'Adequate symptomatic relief' was recorded in 6 of 14 patients on naloxone and 3 of 11 on placebo.
These differences were not significant.
However, 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 were found to improve to a greater extent in patients taking naloxone.
Dr D. Hawkes, of the Prince Charles Hospital, Merthyr Tydfil, Wales, said on behalf of the group, "Preliminary results suggest that naloxone is well tolerated and beneficial in patients with IBS and constipation."
"A larger clinical trial is needed to provide sufficient statistical power to assess efficacy," it was concluded.