Review of Herb-Drug Interactions

January 1999; Volume 2: 11

Source: Miller LG. Herbal medicinals: Selected clinical considerations focusing on known or potential drug-herb interactions. Arch Intern Med 1998;158:2200-2211.

Herbal medicinals are being used by an increasing number of patients who typically do not advise their clinicians of current use. Known or potential drug-herb interactions exist and should be screened for. For example, feverfew, garlic, ginkgo, ginger, and ginseng may alter bleeding time and should not be used concomitantly with warfarin sodium. Ginseng should not be used with estrogens or corticosteroids because of possible additive effects. Valerian should not be used with barbiturates because excessive sedation may occur. Kava when used with alprazolam has resulted in coma.


In this unusual review article, PharmD Miller catalogs commonly used herbal medicinals and associated drug-herb interactions, both theoretical and actual. She first briefly recounts evidence for the effectiveness of chamomile, echinacea, feverfew, garlic, ginger, ginkgo, ginseng, saw palmetto, St. John’s wort, and valerian. She then identifies drugs with a narrow therapeutic window and several herbal interactions with them. Finally, she lists more drugs, herbs, and minerals "with known or potential drug-herb interactions with commonly used herbal medicinals."

This article reads like an impatient life sciences catalog: Dr. Miller has a lot of information and wants to get it all out. But it’s often difficult to differentiate between basic science and clinical cases without referring to the 171 references, which are largely bench laboratory observations and single case reports.

So, this potentially critical article is not well-organized or easy to use—except for the Summary Table of Drug-Herb Interactions of Commonly Used Drugs. Worth review, even with a great deal of room for improvement, the table lists actual and potential herbal interactions with, among others, diuretics (dandelion, uva-ursi, gossypol), hypoglycemics (chromium, karela), iron (chamomile, fev-erfew, St. John’s wort) levothyroxine (kelp, horseradish), NSAIDs (gossypol, uva-ursi), phenobarbital (wormwood, sage, evening primrose oil, borage), phenytoin (see phenobarb), and spironolactone (licorice).


Regard most of the data here with a grain of salt, but review the table noted above on page 2205; it is currently the best of its kind that I know of in the peer-reviewed medical literature.