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

David Gunn, Rabia Topan, Lorna Barnard, Ron Fried, Ivana Holloway, Richard Brindle, Maura Corsetti, 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 FordAmanda J Farrin, Robin Spiller

Research output: Contribution to journalArticlepeer-review


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 - http://www.isrctn.com/ISRCTN17508514.

Original languageEnglish
Pages (from-to)1258-1271
Number of pages14
JournalAlimentary Pharmacology & Therapeutics
Issue number11
Early online date3 Mar 2023
Publication statusPublished - 1 Jun 2023


  • Humans
  • Irritable Bowel Syndrome/complications
  • Ondansetron/therapeutic use
  • Diarrhea/diagnosis
  • Double-Blind Method
  • Feces
  • Treatment Outcome
  • Randomized Controlled Trials as Topic


Dive into the research topics of 'Randomised, placebo-controlled trial and meta-analysis show benefit of ondansetron for irritable bowel syndrome with diarrhoea: The TRITON trial'. Together they form a unique fingerprint.

Cite this