Systematic review and meta-analysis: efficacy of peppermint oil in irritable bowel syndrome

Background: Irritable bowel syndrome (IBS) is one of the most common disorders of gut-brain interaction, with a complex pathophysiology. Antispasmodics are prescribed as first-line therapy because of their action on gut dysmotility. In this regard, peppermint oil also has antispasmodic properties. Aim: To update our previous meta-analysis to assess efficacy and safety of peppermint oil, particularly as recent studies have cast doubt on its role in the treatment of IBS. Methods: We searched the medical literature up to 2nd April 2022 to identify randomised controlled trials (RCTs) of peppermint oil in IBS. Efficacy and safety were judged using dichotomous assessments of effect on global IBS symptoms or abdominal pain, and occurrence of any adverse event or of gastro-oesophageal reflux. Data were pooled using a random effects model, with efficacy and safety reported as pooled relative risks (RRs) with 95% confidence intervals (CIs). Results: We identified 10 eligible RCTs (1030 patients). Peppermint oil was more efficacious than placebo for global IBS symptoms (RR of not improving = 0.65; 95% CI 0.43–0.98, number needed to treat [NNT] = 4; 95% CI 2.5–71), and abdominal pain (RR of abdominal pain not improving = 0.76; 95% CI 0.62–0.93, NNT = 7; 95% CI 4–24). Adverse event rates were significantly higher with peppermint oil (RR of any adverse event = 1.57; 95% CI 1.04–2.37). Conclusions: Peppermint oil was superior to placebo for the treatment of IBS, but adverse events were more frequent, and quality of evidence was very low. Adequately powered RCTs of peppermint oil as first-line treatment for IBS are needed.