Some IBS drugs may do more harm than good, new study suggests

Some medications considered effective against irritable bowel syndrome (IBS) may actually increase the risk of treatment discontinuation, according to a new study in the American Journal of Gastroenterology, suggesting that symptom relief alone should not be the sole factor guiding IBS treatment decisions.According to the researchers, some IBS guidelines focus primarily on the therapeutic effect of IBS medications when making recommendations, without necessarily considering potential harms. To explore that gap, the team reviewed approximately 50 clinical studies evaluating IBS pharmacotherapies. But rather than relying on NNT (number needed to treat), they looked at NNH (number needed to harm), that is, the number of patients needed to treat to cause an adverse effect that leads to treatment discontinuation.Using that measure, some medications widely viewed as effective for IBS appeared less favourable when tolerability was taken into account.This was the case for tricyclic antidepressants: while associated with a low NNT, they also had one of the highest discontinuation rates due to adverse effects, with an NNH of 24. For relieving irritable bowel syndrome with predominant constipation (IBS-C), tenapanor had the highest risk of treatment discontinuation, in addition to having an NNH of 16, compared to 59 for plecanatide and 53 for lubiprostone, treatments that were much better tolerated by the participants.When isolating treatments for IBS with predominant diarrhea (IBS-D), alosetron ranked lowest with a number needed to treat (NNH) of 14 and a discontinuation risk due to side effects of 2.18 (95% CI 1.71–2.76) compared to the placebo group. In the same treatment category, rifaximin performed significantly better, with a higher discontinuation risk in the placebo group than in the treated group.Overall, rifaximin proved to be the safest treatment, supporting its use as first-line therapy for patients with moderate to severe IBS.A switch in symptomsIronically, the most common side effect of IBS-C medications was diarrhea, while the most frequently encountered adverse effect in IBS-D treatment was constipation.Researchers also lamented that most treatments were developed to address only the dominant symptom of IBS. For example, treatments for diarrhea aim to reduce the frequency of bowel movements, not to achieve a regular frequency.“If a patient has six bowel movements a day, a drug that causes constipation—say one bowel movement every three days—would be more likely to be approved,” said the authors of the meta-analysis.“This presents a problem: drugs that cause excessive constipation or diarrhea simply reverse the clinical picture of IBS and lead to patient dissatisfaction, prompting them to discontinue treatment.” ReferenceBusam, Jonathan A. MD, MBA; Batta, Nisha MD, MS; Shah, Eric D. MD, et al. The Safety of Pharmacotherapy for Irritable Bowel Syndrome: A Systematic Review and Meta-Analysis. The American Journal of Gastroenterology 121(3):p 745-753, March 2026. DOI: 10.14309/ajg.0000000000003572 This article was initially published on our sister site ProfessionSanté.ca and has been translated from its original French.

Some IBS drugs may do more harm than good, new study suggests

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