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Randomised, placebo‐controlled trial and meta‐analysis show benefit of ondansetron for irritable bowel syndrome with diarrhoea: The TRITON trial

Gunn, David; Topan, Rabia; Barnard, Lorna; Fried, Ron; Holloway, Ivana; Brindle, Richard; Corsetti, Maura; Scott, Mark; Farmer, Adam; Kapur, Kapil; Sanders, David; Eugenicos, Maria; Trudgill, Nigel; Whorwell, Peter; Mclaughlin, John; Akbar, Ayesha; Houghton, Lesley; Dinning, Phil G.; Aziz, Qasim; Ford, Alexander C.; Farrin, Amanda J.; Spiller, Robin


David Gunn

Rabia Topan

Lorna Barnard

Ron Fried

Ivana Holloway

Richard Brindle

Mark Scott

Adam Farmer

Kapil Kapur

David Sanders

Maria Eugenicos

Nigel Trudgill

Peter Whorwell

John Mclaughlin

Ayesha Akbar

Lesley Houghton

Phil G. Dinning

Qasim Aziz

Alexander C. Ford

Amanda J. Farrin

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Professor of Gastroenterology


Summary: Background: Ondansetron may be beneficial in irritable bowel syndrome with diarrhoea (IBS‐D). Aim: To conduct a 12‐week parallel group, randomised, double‐blind, placebo‐controlled trial of ondansetron 4 mg o.d. (titrated up to 8 mg t.d.s.) in 400 IBS‐D patients. Primary endpoint: % responders using the Food and Drug Administration (FDA) composite endpoint. Secondary and mechanistic endpoints included stool consistency (Bristol Stool Form Scale) and whole gut transit time (WGTT). After literature review, results were pooled with other placebo‐controlled trials in a meta‐analysis to estimate relative risks (RR), 95% confidence intervals (CIs) and number needed to treat (NNT). Results: Eighty patients were randomised. On intention‐to‐treat analysis, 15/37 (40.5%; 95% CI 24.7%–56.4%) met the primary endpoint on ondansetron versus 12/43 (27.9%; 95% CI 14.5%–41.3%) on placebo (p = 0.19). Ondansetron improved stool consistency compared with placebo (adjusted mean difference − 0.7; 95% CI −1.0 to−0.3, p < 0.001). Ondansetron increased WGTT between baseline and week 12 (mean (SD) difference 3.8 (9.1) hours, versus placebo −2.2 (10.3) hours, p = 0.01). Meta‐analysis of 327 patients from this, and two similar trials, demonstrated ondansetron was superior to placebo for the FDA composite endpoint (RR of symptoms not responding = 0.86; 95% CI 0.75–0.98, NNT = 9) and stool response (RR = 0.65; 95% CI 0.52–0.82, NNT = 5), but not abdominal pain response (RR = 0.95; 95% CI 0.74–1.20). Conclusions: Although small numbers meant the primary endpoint was not met in this trial, when pooled with other similar trials meta‐analysis suggests ondansetron improves stool consistency and reduces days with loose stool and urgency. Trial registration –


Gunn, D., Topan, R., Barnard, L., Fried, R., Holloway, I., Brindle, R., …Spiller, R. (2023). Randomised, placebo‐controlled trial and meta‐analysis show benefit of ondansetron for irritable bowel syndrome with diarrhoea: The TRITON trial. Alimentary Pharmacology and Therapeutics, Article 17426.

Journal Article Type Article
Acceptance Date Feb 7, 2023
Online Publication Date Mar 3, 2023
Publication Date Mar 3, 2023
Deposit Date Feb 9, 2023
Publicly Available Date Mar 4, 2024
Journal Alimentary Pharmacology and Therapeutics
Print ISSN 0269-2813
Electronic ISSN 1365-2036
Publisher Wiley
Peer Reviewed Peer Reviewed
Article Number 17426
Public URL
Publisher URL


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