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If you’re like many people, you take your morning vitamin tablet, and follow it with some sort of herbal remedy. Maybe a little gingko biloba? Some melatonin? How about a St. John’s wort tablet?
But how much do you really know about the effects and side effects of herbal compounds?
Dr. Stephen Piscitelli wanted to know more. In collaboration with NIAID, he conducted a study of St. John’s wort, and what he found is sounding a cautionary note for people who take herbal preparations.
Dr. Piscitelli, coordinator of the Clinical Pharmacokinetics Research Laboratory of the Clinical Center’s Pharmacy Department, and his colleagues found that St. John’s wort significantly reduced the blood levels of a drug called indinavir, one of a class of drugs called protease inhibitors taken by many patients with HIV/AIDS.
The main ingredient in St. John’s wort, hypericin, is thought to speed up indinavir’s metabolism. Consequently, not enough indinavir remains in the blood to do the job it’s designed to do. “The low blood levels also can lead to drug resistance,” said Dr. Piscitelli. The study, conducted among eight healthy volunteers, first measured the amount in the body of the drug indinavir when taken alone.
Next, study participants were given only St. John’s wort for two weeks.
Finally, indinavir and St. John’s wort were given together.
“The results were dramatically conclusive,” Piscitelli noted. “All the participants showed a marked drop in blood levels of indinavir after taking St. John’s wort. The drop ranged from 49 percent to 99 percent.”
Researchers in Switzerland also published data indicating that St. John’s wort reduced the blood levels of cyclosporine, a drug used after organ transplantation to prevent rejection.
Dr. Piscitelli’s findings, published in the Feb. 12, 200, “Lancet,” a British medical journal, generated a flurry of media attention last month.
He granted interviews to over 15 news organizations, and appeared on “Good Morning America.”
Dr. Piscitelli’s collaborative research between the CC and NIAID has focused on how antiretroviral and cytokine therapies are metabolized by the body, and evaluations of drug interactions. After learning of case reports, anecdotal evidence, and research data that all suggested a drug interaction with St. John’s wort, he thought this study seemed a logical choice to pursue.
“Depression is a common problem in the HIV-infected population, and St. John’s wort has been used and studied for depression.” A survey of the 0P8 HIV clinic patients identified about 10 percent who had used St. John’s wort. “There could be thousands of patients worldwide who are taking St. John’s wort and antiretroviral drugs,” he said.
But users of complementary health practices often do not confide these facts to their physicians, he pointed out. “Patients may assume the doctor will have a negative reaction.”
There may be a basis for that reaction, however. Herbals are unregulated in this country. As a result, little hard science exists to support claims of either benefit or harm.
“These compounds don’t go through the rigorous testing that pharmaceuticals do, they don’t have to prove safety or efficacy, and they are considered dietary supplements, not drugs, so they can bypass all the standard testing which prescription and over-the-counter drugs have to go through. So it’s ‘buyer beware,”’ said Dr. Piscitelli. “There is a general misconception among the public that these herbal products have no adverse effects and no drug interactions. Our study clearly shows that there can be dangerous interactions between these products and other drugs,” he said.
Dr. Piscitelli urges health professionals to ask their patients what herbals they may be taking—and be open-minded to the response.
Conversely, patients should provide this information even if they are not specifically asked.
Dr. Piscitelli and his colleagues are currently looking at other widely used herbal preparations, including garlic, melatonin, gingko biloba, kava kava, and saw palmetto, to see if any similar drug interactions occur. “These are the most widely used of the herbal remedies and may have the greatest impact on public health.
Also, there is existing evidence that these compounds may affect drug metabolism,” he said.
Other collaborators on the study included Dr. Aaron Burstein and Raul Alfaro from the Clinical Center Pharmacy Department, and Dr. Judith Falloon and Doreen Chaitt from NIAID.
For more information on Dr. Piscitelli’s upcoming studies, or to be considered for participation, contact the Clinical Research Volunteer Program at 1-800-892-3276.
by Sue Kendall