Popular Herb May Interfere with Cancer Drug
St. John's wort, an herb thought to be a safe, natural remedy for mild depression, may interfere with a powerful cancer-fighting drug's ability to prevent relapse in leukemia patients, according to a University of Florida pharmacy researcher. His findings were reported at the annual meeting of the American Society for Clinical Pharmacology and Therapeutics, held in March 2004.
Researchers studied healthy volunteers to determine whether the herbal preparation interacted with the prescription drug imatinib mesylate (Gleevec[R]). It was found that taking the two drugs together caused the amount of imatinib in the blood to drop by nearly 30 percent.
"A 30 percent decrease in the level of Gleevec[R] is significant to cancer patients," said Reginald F. Frye, Ph.D., associate director for the university's Center of Pharmacogenomics. "It is the same as lowering the dose--which is enough to allow for a relapse in the cancer growth."
"The emergence of studies such as this shows the need for health care professionals to have current scientific information on the safety and efficacy of natural supplements," said Veronika Butterweck, the DeSantis professor of natural products at the College of Pharmacy.
Patients should be aware that any product they take, whether herbal, nonprescription, or prescription, has the potential to alter how their body handles other drugs they are taking, said study collaborator Dr. Merrill J. Egorin, co-director of the Molecular Therapeutics and Drug Discovery Program at the University of Pittsburgh Cancer Institute.
"The interactions of herbal preparations and even certain foods can be an important factor in how well a patient may absorb or metabolize certain drugs, and those differences can have important clinical consequences," he said.
Clinical trials of St. John's wort in the U.S. show that although it does not appear useful for major depression, it might be helpful for mild depression, Dr. Frye said.
The first indication that St. John's wort interacted with other medications came after physicians noted that drugs designed to prevent organ rejection were not as effective in transplant patients who were taking the herbal supplement, he added. A few years ago, the Food and Drug Administration (FDA) issued a public health advisory after federal research showed that St. John's wort interfered with medicines taken by patients with human immunodeficiency virus (HIV) infection. …