ST. JOHNS WORT

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

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.”