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A Dangerous Prescription

Herbs can harm, especially when taken with traditional drugs.

WebMD Feature

April 17, 2000 (San Francisco) -- When 71-year-old Doris Sargent couldn't sleep last year, she turned to her grocery store for something safe and natural: St. John's wort. "I'd heard it was the poor man's Prozac," she says.

Because Sargent had had a kidney transplant a few years earlier, she asked her kidney specialist about the St. John's wort and several other supplements she took, just to be safe. He indicated he didn't know much about them, but added that if she thought they helped, they probably couldn't hurt.

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It turns out both may have been wrong.

Researchers have long suspected that herbs and prescription drugs can interact, but a recent study has found that mixing the two can cause more harm than anyone had realized. In the February 12 issue of Lancet, Swiss researchers reported that St. John's wort, a top-selling herb used to treat depression and other maladies, seemed to interfere with the metabolism of cyclosporine, an anti-rejection drug given to transplant patients.

In the same issue of Lancet, St. John's wort was found to reduce the effectiveness of the AIDS drug indinavir, according to researchers at the Clinical Pharmacokinetics Research Laboratory at the National Institutes of Health (NIH). Apparently St. John's wort can influence the body's ability to break down or flush critical drugs out of the body quickly, so that people with AIDS -- and perhaps those with transplanted organs, like Sargent -- get only half their needed dose.

"No one has ever considered these herbal drugs to have an effect. They think, 'Oh, it's natural, it must be safe.' But there aren't many substances that do only good things," says Stephen Piscitelli, PharmD, who led the indinavir study.

What's more, the Food and Drug Administration (FDA) now warns that St. John's wort may interfere with the body's metabolism of prescription drugs used to treat a host of common ailments, including heart disease, high blood pressure, depression, and certain cancers. Estrogen and Viagra may also be affected.

The news stunned patients like Sargent, who is among at least 15 million Americans who take dietary supplements along with prescription drugs, according to a survey published in the November 11, 1998 issue of the Journal of the American Medical Association. More significantly, the findings have also jump-started new research on the interactions between supplements and prescription drugs -- an area that until now has received little scrutiny.

Piscitelli and his colleagues already are testing St. John's wort against other drugs vital for people with transplanted organs, heart disease, high blood pressure, depression, and some cancers. Researchers in his lab have also started a fast-track program to systematically test several other popular herbs for interactions with common prescription drugs. They will next examine melatonin, a hormone that helps some people sleep; ginkgo biloba, an herb used to boost memory; and garlic, which many people take to lower cholesterol. Later, they'll test kava kava, an herb used to reduce anxiety, and saw palmetto, a berry used to relieve the symptoms of prostate enlargement. They plan to publish their results beginning this summer.

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