The Pharmaceutical Journal Vol 267 No 7177 p805-809
8 December 2001

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More research on the occurrence of herb-drug interactions is needed

Herb-drug interactions occur but are under-researched, a review of reported interactions shows.

By searching four electronic databases and data from manufacturers, Professor Adriane Fugh-Berman, George Washington University of Medicine, Washington DC, and Professor Edzard Ernst, School of Postgraduate Medicine and Health Sciences, University of Exeter, identified 108 cases of suspected interactions between herbal products and medicinal products. Warfarin was found to be the most common drug involved in such interactions and St John’s wort was the most common herb involved. Fifty-four cases out of the 85 cases of interactions reported with St John’s wort were with ciclosporin. Other reports involving St John’s wort included 12 cases of interactions with oral contraceptives, nine with antidepressants and seven with warfarin.

The researchers conclude that patients taking St John’s wort or anticoagulants are at highest risk of an interaction. They say that patients on coumarin anticoagulants should be specifically advised to avoid taking herbal medicines or to have their international normalised ratio measured within two weeks of starting the product. Patients taking garlic, ginkgo, danshen or other herbal medicinal products affecting platelet function should also be monitored.

The review was published in the British Journal of Clinical Pharmacology (2001;52:587).

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