A Dangerous Prescription

Last Editorial Review: 1/30/2005

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.

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.

In the tests, volunteers will get a standard dose of the supplement along with a standard dose of the prescription drug. Then the researchers will draw blood several times over the course of the day to look for unwanted interactions. Such rapid screening won't reveal subtle long-term problems, but it should give researchers a hint of which herbs are best left on the shelf by some patients.

Other researchers are also beginning to look at the potential risks of herbs. Stephen Straus, MD, the new director of the NIH's National Center for Complementary and Alternative Medicine, has vowed to subject more herbal remedies to clinical study. And some patient advocates are calling on the FDA to begin regulating supplements -- a move that would force the manufacturers to pay for research into side effects and interactions with other drugs. (See In My Opinion: Herbal Lessons From Germany)

For now, though, patients like Doris Sargent are on their own. Sargent stopped taking St. John's wort as soon as she heard the findings earlier this year. She immediately went in for a blood test. Fortunately, the cyclosporine she takes to prevent rejection of her kidney was still doing its job.

She says she won't take St. John's wort again, but has no intention of dropping her other herbal supplements. "I think they're gentler than [prescription] drugs," she says. "I just wish I had access to good information about them."

Jayne Garrison is a senior editor at WebMD.

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