[Drug interactions of Hypericum perforatum (St. John's wort) are potentially hazardous]

Hypericum can lower the plasma levels of simultaneously administered drugs by induction of metabolism. Combinations of hypericum products with warfarin, cyclosporin, oral contraceptives, theophylline, fenprocoumon, digoxin and indinavir have led to reported interactions and reduced therapeutic activity. It is therefore not advisable to combine hypericum products with other drugs, especially CYP3A4 and p-glycoprotein substrates. Discontinuing hypericum after protracted use may lead to higher plasma levels of the drugs used simultaneously, with the risk of adverse effects. Registered homeopathic preparations with a dilution of 1 in 10,000 or weaker may be regarded as safe.