NCPA - National Center for Policy Analysis


June 24, 2004

Several recent studies suggest that taking certain herbal supplements--like St. John's Wort, Echinacea, and ginkgo biloba--may interfere with common prescription drugs.

While much of the research is still emerging, so far researchers have found that:

  • St. John's Wort, an herbal anti-depressant, appears to weaken the effectiveness of birth-control pills, protease inhibitors, and immunosuppressants.
  • Ginkgo biloba may cause bleeding episodes if combined with blood-thinning drugs like Warfarin.
  • Calcium-fortified orange juice and mineral-rich cereals like Total may interfere with the absorption of antibiotics like Cipro and tetracycline.

Some pharmaceutical companies are now listing herbal interactions on their drug labels, and some herbal companies are doing the same. Companies are also launching databases to allow doctors and pharmacists to check for herbal interactions with the drugs they prescribe. Lexi-Corp, Inc., for example, sells herbal-interaction software that pharmacists can run on handheld computers like the Palm Pilot.

Source: Jane Spencer, "The Risks of Mixing Herbs and Drugs," Wall Street Journal, June 22, 2004.

For text WSJ text (subscription required),,SB108784932749743204,00.html


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