Mother Earth Living

St. John's Wort: Be Aware

By Amy Baugh-Meyer and Kelli Rosen
May/June 2000

St. John’s wort is generally safe, but use caution when taking certain medications.


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On February 10, the newspapers were buzzing about new pieces of research involving St. John’s wort. Headlines read, “Two studies fault St. John’s wort”; “Popular herb becomes target of warning”; and “FDA cautions about St. John’s wort.”

Causing all the hype were two small samples, of eight and two people respectively, which found that St. John’s wort (Hypericum perforatum) may interfere with drugs used to treat HIV patients and people who have had heart transplants.

“The mass media is quick to jump on any negative tidbit they can get on an herb,” says Steven Foster, Herbs for Health lead editorial adviser and author of 101 Medicinal Herbs (Interweave Press, 1998).

However, Foster and other herbalists were not surprised by the findings.

Mark Blumenthal, executive director of the American Botanical Council and an Herbs for Health adviser, says other data has been published prior to these studies that backs up theories that St. John’s wort affects drug metabolism.

“It’s inevitable to get new reports of drug interactions that could not have been predicted in clinical studies, because more people in the general population are now taking St. John’s wort,” says Blumenthal. “We’re probably going to see even more interactions in the future.”

What the Research Means

The HIV researchers gave eight HIV-negative subjects a protease inhibitor called indinavir for three days. On the third day, the subjects began taking St. John’s wort, then they took both indinavir and the herb for two weeks. Research showed that blood concentrations of indinavir dropped an average of 57 percent when taken with St. John’s wort. In the second sample, two Swiss heart transplant patients were found to have lower-than-normal levels of the antirejection drug cyclosporine in their blood after taking St. John’s wort.

Robert Rountree, M.D., explains the effects. “Both indinavir and cyclosporine are metabolized by cytochrome 3A4—part of the cytochrome enzyme system, which metabolizes numerous drugs. I suspect that there is some ingredient in standardized St. John’s wort that induces, or activates, this enzyme, leading to faster clearing of the drug from the bloodstream.”

Rountree says he sees no reason to question the interaction between the drugs and St. John’s wort.

“I think the effect is real despite the low numbers of people involved [in the samples],” he says. “But I don’t see why that makes St. John’s wort ‘dangerous.’ You certainly don’t see that adjective applied to the many medications that affect this enzyme. Additionally, grapefruit juice is well known to inhibit cytochrome 3A4 isoenzyme, thus having the exact opposite effect of St. John’s wort.”

Steven Dentali, Ph.D., senior director of botanical studies at Rexall Sundown, believes, along with Foster, Blumenthal, and Rountree, that this is not a safety issue but an herb-drug interaction issue. Blumenthal points out that St. John’s wort has been shown to be safe for general use in more than two dozen published studies.

“These latest findings are not something we should be frightened of,” Dentali says. “It’s important information to know and it should be put into perspective.”

How will these results affect St. John’s wort product manufacturers? Michael McGuffin, president of the American Herbal Products Association, says his organization is seriously considering whether they should recommend that cautionary label statements be placed on St. John’s wort products.

“We’ll continue to look at this and other data to see if a cautionary label statement is substantiated,” McGuffin says.

The general consensus among our sources is that you should let your physician or health-care practitioner know if you’re taking St. John’s wort and discuss any possible interactions with them.


By Amy Baugh-Meyer and Kelli Rosen

Both are Herbs for Health’s assistant editors.


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