Prescriptions foiled by St. John's Wort

Herbal antidepressant use can pose problem

(CNN) -- Use of the herbal antidepressant St. John's Wort could have a negative effect on some prescription medicines, authorities say.

A study by the National Institutes of Health found the popular supplement can decrease the effectiveness of a variety of prescription medications used to treat HIV and AIDS, some cancers, heart disease and organ-transplant patients. The herb also has been estimated to decrease the effectiveness of birth control pills by as much as half.

"The interaction with other medications are very clinically important and the list of medications that interact with St. John's Wort is growing," said internist Deborah Kelly.

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The standard of care in HIV treatment is the use of protease inhibitors such as indinavir, amprenavir, nelfinavir, ritonavir and saquinavir. The effectiveness of these and other drugs depend on a "metabolic pathway" called "cytochrome P450," NIH said.

"If St. John's Wort is given with a prescription drug, there is a possibility that the blood levels of that prescription drug may go way down," said NIH's Stephen Piscitelli. "That could lead to clinical consequences."

Because treatments used for such varied conditions as heart disease, seizures, depression, certain cancers and transplant-rejection use the same metabolic pathway, there is evidence that St. John's Wort could also have a detrimental effect on those drugs, NIH said.

St. John's Wort is currently available in a wide array of products, including teas, drinks and other so-called functional foods.

Although the U.S. Food and Drug Administration is working with manufacturers of protease inhibitors to include interaction warnings with their packaging, there currently are no laws requiring products containing St. John's Wort to be labeled as such.

"Still, our industry is concerned about these interactions," said John Cardellina, spokesman for the Council for Responsible Nutrition. "People who are taking protease inhibitors for HIV therapy and immunosuppressant drugs for organ transplants are both classes of patients that are likely to be mildly to moderately depressed."

Using St. John's Wort in conjunction with other antidepressants can also result in serotonin overload, which can cause tremors, headaches and restlessness.

CNN Medical Correspondent Linda Ciampa contributed to this report.

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Food and Drug Administration
National Center for Complementary and Alternative Medicine
Journal of the American Medical Association

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