Ondansetron Works for Diarrhea-Predominant Irritable Bowel Syndrome

Summary and Comment |
February 4, 2014

Ondansetron Works for Diarrhea-Predominant Irritable Bowel Syndrome

  1. Douglas K. Rex, MD

This 5-HT3 receptor antagonist improved stool consistency and symptoms, with a low frequency of severe constipation.

  1. Douglas K. Rex, MD

Ondansetron is a 5-hydroxytryptamine 3 receptor antagonist (5-HT3RA) used for the treatment of nausea and vomiting. 5-HT3RAs also cause constipation, and one of these agents, alosetron, is approved for the treatment of diarrhea-predominant irritable bowel syndrome (IBS-D).

To assess the efficacy of ondansetron in treating IBS-D, investigators randomized 120 patients to receive ondansetron (one to two 4-mg pills, two to three times daily, as titrated by the patient) or placebo for 5 weeks in a double-blind, crossover study.

After completing 5 weeks of treatment with ondansetron or placebo, patients underwent a 2–3 week washout period, followed by 5 weeks of the alternate treatment. The primary endpoint was average stool consistency during the last 2 weeks of treatment, as documented with the Bristol Stool Form score. Transit time was measured in the last week of each treatment.

Compared with placebo, ondansetron use resulted in the following:

  • Greater improvement in stool consistency, fewer days with fecal urgency, less urgency, fewer bowel movements, and less bloating

  • A greater decrease in the IBS symptom severity score (83 vs. 37; P=0.001) but no difference in pain score

  • A higher rate of reported adequate relief (65% vs. 14%)

  • A higher rate of constipation (9% vs. 2%), resulting in 2% of patients dropping out of the study

  • Longer transit time (10 hours longer than with placebo)


These findings support the use of ondansetron as a new agent in the armamentarium for treating diarrhea-predominant irritable bowel syndrome.

Editor Disclosures at Time of Publication

  • Disclosures for Douglas K. Rex, MD at time of publication Consultant / Advisory board Exact Sciences; Ferring Pharmaceuticals; Given Imaging; Olympus Speaker’s bureau Boston Scientific; Braintree; Ferring Pharmaceuticals Grant / research support Battelle; Braintree; Northwestern University; Olympus America Editorial boards Annals of Gastroenterology and Hepatology; Comparative Effectiveness Research; Expert Review of Gastroenterology and Hepatology; Gastroenterology; Gastroenterology and Hepatology News; Gastroenterology Report; Gastroenterology Research and Practice; Journal of Clinical Gastroenterology; Techniques in Gastrointestinal Endoscopy; World Journal of Gastroenterology; World Journal of Gastrointestinal Oncology; World Journal of Gastrointestinal Pathophysiology; World Journal of Gastrointestinal Pharmacology and Therapeutics


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