Influence of menthol on first pass elimination [Influencia del mentol sobre la eliminación de primer paso]

Menthol is one of the most widely consumed essential oils. In vitro and in vivo studies indicate that menthol induces or inhibits drug metabolizing activities of liver or gut; thus it could decrease or increase serum drug concentrations. In vitro studies demonstrate that menthol has a relaxant effect on the gastrointestinal tract, thus it could influence the rate of drug absorption. Also in vitro Caco-2 model study results suggest that peppermint oil (30-55% of which is menthol) has inhibitory effect on the functionality of intestinal P-glycoprotein related efflux carriers, which could affect the amount of absorbed drug. This paper will focus on the effect of menthol on the first pass elimination of drugs. This issue is stressed, because it could change pharmacological responses of various drugs.