Randomised, Placebo-controlled Trial and Meta-analysis Show Benefit of Ondansetron for Irritable Bowel Syndrome with Diarrhoea: The TRITON Trial

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 4mg o.d. (titrated up to 8mg 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: 80 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, -0.3, p