Effect of peppermint oil and caraway oil on gastrointestinal motility in healthy volunteers: a pharmacodynamic study using simultaneous determination of gastric and gall-bladder emptying and orocaecal transit time

Background: Although peppermint oil and caraway oil are frequently used in herbal drugs for abdominal discomfort and pain, the pharmacological insights into their effects on the gastrointestinal tract are poor. Methods: The pharmacodynamic effects of 90 mg peppermint oil (WS 1340) and 50 mg caraway oil (WS 1520) on the motility of the stomach and gall-bladder, and on the orocaecal transit time, in comparison with placebo, 10 mg cisapride and 10 mg n-butylscopolamine, were studied in 12 healthy volunteers. The study involved simultaneous ultrasonic determination of gastric and gall-bladder emptying, together with assessment of the orocaecal transit time using the lactulose H-2 breath test. The combination of these methods allows three gastrointestinal organs to be studied in one subject simultaneously. Results: The antral filling time was comparable with placebo, peppermint oil, caraway oil and cisapride, whereas it was significantly shortened (P = 0.04, two-sided paired t-test) with n-butylscopolamine. The gastric emptying time did not differ significantly between placebo, peppermint oil, caraway oil and cisapride, but was significantly prolonged by n-butylscopolamine (P = 0.04, two-sided paired t-test). Complete inhibition of gall-bladder emptying was caused by both oils and n-butylscopolamine. Cisapride significantly shortened gall-bladder emptying compared with placebo (P = 0.02, two-sided signed rank test). The orocaecal transit time was significantly prolonged by peppermint oil (P = 0.004) and n-butylscopolamine (P = 0.002), but not significantly prolonged by caraway oil (P = 0.06); it was significantly shortened by cisapride (P = 0.04, all two-sided paired t-test). Conclusions: Peppermint oil and caraway oil show a relaxing effect on the gall-bladder and the former slows small intestinal transit. Further studies should investigate the effects of both oils on a maximal contraction stimulus on the gall-bladder, and in patients suffering from motility disorders.