title: [Pharmacokinetic drug interactions by herbal drugs: Critical evaluation and clinical relevance].
abstract: Pharmacokinetic herb-drug interactions are caused by an induction or inhibition of cytochrome P450 (CYP) enzymes or transporters e.g. P-glycoprotein. St. John's wort extracts containing hyperforin increase the expression of CYP-enzymes and P-glycoprotein mainly in the gut and liver which leads to a clinically relevant decrease of the bioavailability of CYP and P-glycoprotein substrates. Contrarily, the bioactivation of the prodrug losartan is reduced by milk thistle extracts which is due to an inhibition of CYP2C9. However, the 15 % reduction of the bioavailability of the active metabolite E-3174 is clinically not relevant. Also, minor changes in drug bioavailability observed in clinical studies for valerian, echinacea, ginkgo and hawthorne are clinically not relevant, although in vitro studies point to drug interactions in vivo. Since for herbal extracts a positive in vitro - in vivo correlation regarding the impact on drug bioavailability is rare, results from in vitro studies should be carefully interpreted.
authors.affiliation: Institut für Pharmazie und Lebensmittelchemie, Julius-Maximilians-Universität Würzburg, Würzburg, Germany. m.unger@pharmazie.uni-wuerzburg.de
authors.forename: Matthias
authors.initials: M
authors.lastname: Unger
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D001189:Aryl Hydrocarbon Hydroxylases / Q000037:antagonists & inhibitors / Q000378:metabolism; D001682:Biological Availability; D002986:Clinical Trials as Topic; D065729:Cytochrome P-450 CYP2C9; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004790:Enzyme Induction / Q000187:drug effects; D041743:Herb-Drug Interactions / Q000502:physiology*; D006801:Humans; D020902:Hypericum; D019808:Losartan / Q000009:adverse effects / Q000493:pharmacokinetics / Q000627:therapeutic use; D020944:Silybum marianum; D008517:Phytotherapy / Q000009:adverse effects*; D010936:Plant Extracts / Q000009:adverse effects* / Q000493:pharmacokinetics* / Q000627:therapeutic use
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D065607:Cytochrome P-450 Enzyme Inhibitors; D010936:Plant Extracts; D003577:Cytochrome P-450 Enzyme System; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases; D019808:Losartan