Frequently Asked Questions

Can herbs interact with any of the chemotherapy drugs?

A small study of 5 patients at the Rotterdam Cancer Institute in the Netherlands has recently been published in which it was shown that concurrent administration of a typical dose of St. John's wort (300 mg three times per day) with the chemotherapy drug Camptosar decreased the blood levels of Camptosar's active metabolite by 42%. In addition, and even more worrisome, these decreased levels were still seen as long as 3 weeks after stopping the St. John's wort. (Effects of St. John's Wort on Irinotecan Metabolism. J Natl Cancer Inst. 2002 Aug 21;94(16):1247-9. Mathijssen RH, Verweij J, De Bruijn P, Loos WJ, Sparreboom A.)

St. John's wort increases the type of enzymes in our body that metabolize many drugs, thus lowering levels of these drugs in our bloodstream. The authors of this study state that more than 50% of current anti-cancer drugs are metabolized by the same enzymes that were affected by St. John's wort in their research. Some examples would be Tamoxifen, Cytoxan, Etoposide, Vincristine, and the taxanes like Taxol and Taxotere. Thus, taking St. John's wort during chemotherapy, and also before chemotherapy begins, can have the potential to lower the level of these chemotherapy drugs, possibly reducing their effectiveness to the point of treatment failure.

This is a perfect example why a discussion about the use of all complementary therapies, which includes all herbs and other dietary supplements, with your oncologist (and also your surgeon) is critical. Don't wait for him (her) to ask, and just as importantly, if he asks you, tell the truth about what you are using. As more and more research is done, problematic herb-drug interactions that decrease the levels and potential effectiveness of chemotherapy (or also drugs used during surgery) will be determined. Speaking up could initiate a conversation that could help save your life.

The Herb-Drug Interaction Handbook by Sharon Herr, RD, is an exceptionally thorough, up-to date source of herb-drug interactions. More information about the book and ordering information is available on the author's website. In addition, The Natural Health Encyclopedia, available to subscribers at ConsumerLab.com will also provide information on drug-herb interactions.

FAQ posted 4/01, revised 9/02

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These questions and answers are intended to be of a general informative nature. Please consult with the Registered Dietitian in your cancer center or your health care provider for nutritional advice that can be individualized to your specific medical condition.