Portal de Periódicos da CAPES

Safety of St John's wort (Hypericum perforatum)

2000; Elsevier BV; Volume: 355; Issue: 9203 Linguagem: Inglês

10.1016/s0140-6736(05)73225-6

1474-547X

Peter A. G. M. De Smet, Daan J. Touw,

Natural Compound Pharmacology Studies

The commentary by E Ernst1Ernst E Second thoughts about safety of St John's wort.Lancet. 1999; 354: 2014-2016Summary Full Text Full Text PDF PubMed Scopus (288) Google Scholar about the interaction potential of St John's wort needs addition as well as correction. The case series by the Swiss Drug Monitoring Center2Bon S Hartmann K Kuhn M Johanniskraut: Ein Enzyminduktor?.Schweiz Ap Ztg. 1999; 16: 535-536Google Scholar included an interaction with phenprocoumon and not with warfarin. It is therefore important to note that the Swedish authorities have received reports which associate use of St John's wort with a reduced response to warfarin (www.mpa.se/observanda/obs99/johannesort.html) Because the commentary was bound to draw attention from the lay press, more explicit attention should have been paid to the risk that patients on phenprocoumon or digoxin should not injudiciously discontinue St John's wort by themselves, as this could lead to toxic reactions in stabilised patients. The interaction study with digoxin did not confirm induction of hepatic cytochrome P450 by St John's wort, but suggested induction of the drug transporter P-glycoprotein, which mediates the intestinal absorption, distribution, and renal excretion of digoxin.3Johne A Brockmöller J Bauer S Maurer A Langheinrich M Roots I Pharmacokinetic interaction of digoxin with an herbal extract from St John's wort.(Hypericum perforatum). Clin Pharmacol Ther. 1999; 66: 338-345Crossref PubMed Scopus (552) Google Scholar The full report of this study also mentions unpublished data that St John's wort can lower the plasma concentrations of amitriptyline, thereby providing additional evidence that some St John's wort interactions might involve induction of cytochrome P450.4Venkatakrishnan K Greenblatt DJ Von Moltke LL Schmider J Harmatz JS Shader RI Five distinct human ytochromes mediate amitriptyline N-demethylation in vitro: dominance of CYP 2C19 and 3A4.J Clin Pharmacol. 1998; 38: 112-121Crossref PubMed Scopus (140) Google Scholar More research into these mechanisms is important for two reasons. First, because it will help to predict which additional drugs are prone to pharmacokinetic interactions with St John's wort. Second, because it will show whether the antidepressant properties and interactions of St John's wort reside in the same components. Since hyperforin is increasingly recognised as a major active principle of St John's wort,5Chatterjee SS Bhattacharya SK Wonnemann M Singer A Muller WE Hyperforin as a possible antidepressant component of hypericum extracts.Life Sci. 1998; 63: 499-510Crossref PubMed Scopus (447) Google Scholar it would be particularly interesting to test the interaction potential of this constituent.