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, a University of Florida pharmacy researcher will report March 27 at the annual meeting of the American Society for Clinical Pharmacology and Therapeutics.
Researchers who studied healthy volunteers to determine whether the herbal preparation interacts with the prescription drug imatinib mesylate, known by the trade name Gleevec, found that taking the two together caused the amount of Gleevec in the blood to drop nearly 30 percent.
Because it targets only cancerous cells, Gleevec has been called a “magic bullet” drug that fights aggressive cancers such as chronic myelogenous leukemia, researchers say. Leukemia patients who go into remission must continue to take daily oral doses of the medicine to prevent a recurrence.
“A 30 percent decrease in the level of Gleevec is significant to cancer patients,” said Reginald F. Frye, associate director for the UF Center of Pharmacogenomics. “It is the same as lowering the dose - which is enough to allow for a relapse in the cancer growth.”
Frye began the study while he was still working at the University of Pittsburgh Schools of Pharmacy and Medicine, prior to arriving at UF’s College of Pharmacy in 2003.
“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 UF 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,” Egorin said.
Clinical trials performed on St. John’s wort in the United States show that while it doesn’t appear useful for major depression, it may help treat mild depression, Frye said.
The first indication that St. John’s wort interacts with other medications came after physicians noted drugs designed to prevent organ rejection weren’t as effective in transplant patients who were taking the herbal supplement, he added. A few years ago, the U.S. Food and Drug Administration issued a public health advisory after federal research showed St. John’s wort interferes with medicines used to treat patients with HIV. Those findings raised concerns that the herb also might interact with drugs taken by patients with heart disease, depression or seizures.