A 2013 meta-analysis of 9 RCTs with 726 patients compared various doses of enteric-coated peppermint oil with placebo over a minimum of 2 weeks’ treatment.3 Five RCTs with 357 patients (62% female, 13.4% children) demonstrated improvement of abdominal pain in 57% of patients taking peppermint oil compared with 27% receiving placebo (RR=2.1; 95% CI, 1.6-2.8; NNT=4 at 2 to 8 weeks). No statistically significant heterogeneity was identified among the treatment groups.
Pooled analysis found that peppermint oil patients were more likely than placebo patients to experience an adverse event (7 trials; N=474; 22% vs 13%; RR=1.7; 95% CI, 1.3-2.4), but that the events were generally mild and transient. The most frequently reported adverse event was heartburn.