Does horny goat weed have any clinically significant interactions?

· Regional Drug and Therapeutics Centre

Horny goat weed (Epimedium) is a herbal medicine that may comprise of mixtures of different related Epimedium species, which contain numerous and varied active constituents. As herbal products are subject to variations in quality, safety and efficacy, their use should not be recommended routinely.

There is no published human information on drug interactions with horny goat weed. There is, however, the potential for significant drug interactions due to its inhibitory action on certain subgroups of the cytochrome P450 enzyme system, although the degree to which it does so is currently unknown. Drugs with which horny goat weed may interact via this mechanism include warfarin, amitriptyline, clarithromycin and erythromycin, ciclosporin and tacrolimus, and phenytoin. Furthermore, horny goat weed may enhance or prolong the effects of drugs that prolong the QT interval, and there is a potential for an additive interaction with phosphodiesterase 5 inhibitors for erectile dysfunction.

Due to the lack of information of the nature and extent of interactions of horny goat weed in humans, it would be prudent to advise patients to avoid use of the product concurrently with medication until it is more widely studied.

Complementary and alternative therapiesQ&ARenal and urologic disordersSexual health

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