Interaction type : Interactions
Interaction rating : Potential/Theoretical
Peppermint : Mentha piperita L. (Lamiaceae)
Clinical Evidence :
In a crossover study in 11 healthy women, a single 100 mg capsule of menthol (a major constituent of peppermint oil) taken with decaffeinated coffee, to which 200 mg of caffeine was added, had no effect on caffeine pharmacokinetics except for an increase in time to maximum caffeine concentration of about 30 minutes.
The maximum decrease in heart rate seen with caffeine was less in the presence of menthol (about a 4 bpm difference), but menthol had no effect on the small changes in blood pressure seen with caffeine. [1]
Experimental evidence:
One in vitro [2] study and one animal [3] study found that peppermint oil or tea inhibited the cytochrome P450 isoenzyme CYP1A2.
Mechanism :
Experimental evidence [2][3] suggests that peppermint might inhibit cytochrome P450 isoenzyme CYP1A2, for which caffeine is a probe substrate; the clinical evidence with menthol (a major constituent of peppermint oil) found that caffeine metabolism was not altered. Menthol slightly delayed the absorption of caffeine.
Importance and management :
The clinical evidence suggests that peppermint oil might not have clinically relevant effects on the metabolism of substrates of CYP1A2, which would be in keeping with the fact that no such interactions appear to have been reported. Peppermint oil might slightly delay the absorption of caffeine, and presumably other drugs, but the delay of 30 minutes suggests that this is usually unlikely to be clinically relevant.
References :
[1] Gelal A, Guven H, Balkan D, Artok L, Benowitz NL. Influence of menthol on caffeine disposition and pharmacodynamics in healthy female volunteers. European journal of clinical pharmacology. 2003 Sep;59(5):417-22.
[2]Unger M, Frank A. Simultaneous determination of the inhibitory potency of herbal extracts on the activity of six major cytochrome P450 enzymes using liquid chromatography/mass spectrometry and automated online extraction. Rapid communications in mass spectrometry. 2004 Oct 15;18(19):2273-81.
[3]Maliakal PP, Wanwimolruk S. Effect of herbal teas on hepatic drug metabolizing enzymes in rats. Journal of Pharmacy and Pharmacology. 2001 Oct;53(10):1323-9.
