The growing knowledge of St. John's wort (Hypericum perforatum L) drug interactions and their clinical significance

Objective: This review discusses drug interactions with St. John's wort (Hy pericum perforatum L), and their clinical relevance. Background: Herbal medicines are being used by an increasing number of pati ents who typically do not inform their clinicians of concomitant use. Recen t reports indicate that St. John's wort extracts may potentiate certain sub enzymes of the cytochrome P-450 enzyme system. This may decrease the serum concentration of a number of concomitant drugs, including warfarin, digoxin , theophylline, cyclosporin, and oral contraceptives. Several common foods and drinks leg, broccoli, red nine) also influence parts of this same enzym e system. Well-documented cases concern 24 subjects (including 8 healthy vo lunteers) of millions of people treated with Hypericum extracts, thus showi ng a strong underreporting of the effects and safety of herbal medicines. Conclusion: Although evidence is growing on the effectiveness of Hypericum in mild to moderate depression, and its safety has been established in doub le-blind, randomized clinical trials, pharmacovigilance is needed for all h erbal medicines, and a tighter regulatory framework is desirable. Regulator y agencies in the United States and Europe have already issued warnings abo ut Hypericum drug interactions.