How to Avoid Bad Herb and Drug Interactions

Mixing the two can be a dangerous combination


| May-June 1999



Larry Benton was scared. He had read that Asian ginseng might counteract a prescription drug that helps prevent blood clots, and he had been taking that combination for months. But his doctor wouldn’t talk about herbs, and his insurance plan didn’t allow for switching doctors or seeing alternative health care providers. Benton (not his real name) felt he needed both the herb, which gave him a much-needed energy boost, and the prescription medication, a blood thinner called warfarin. Afraid to continue and afraid to stop, he didn't know which way to turn.

Benton’s dilemma illustrates a potentially problematic side of herbal remedies: Combining herbs with pharmaceuticals may result in bad interactions. But finding information is difficult, and medical doctors are often hesitant to offer advice. Part of the problem is that Western science is just beginning to produce the research that doctors rely on to make such health care decisions.

“Consumers are not well served by our medical climate,” says Amanda McQuade Crawford, a medical herbalist, president of the National College of Phytotherapy in Albuquerque, and founding member of the American Herbalists Guild. Yet herb-drug combinations offer many benefits—provided they are prescribed and used carefully.

Health care practitioners prescribe herb-drug combinations for many reasons, including using herbs to ease side effects from harsh, though potentially life-saving, pharmaceuticals. They also use herbs to strengthen the effects of pharmaceuticals (allowing for a lower dose) and help patients withdraw from addictive or potentially harmful drugs. McQuade Crawford, for example, once helped a client who was taking antiviral drugs and a strong diuretic called Lasix to treat hepatitis C, a viral disease that inflames the liver.

“As the doctors kept increasing his Lasix, he became more frightened, and they became more pessimistic in their prognosis,” she says. Along with exercise, stress management, and changes in diet, McQuade Crawford recommended that her client augment his drug regimen with potassium-rich dandelion leaf and silymarin, the active compounds in milk thistle. In three months, he no longer needed the prescription diuretic, and medical tests showed his condition had improved.

Donald Brown, a naturopathic doctor and author of Herbal Prescriptions for Better Health (Prima, 1996), prescribes herbs to buffer side effects of strong medical treatments. He has, for example, advised chemotherapy patients to use astragalus and Siberian ginseng to help their bone marrow produce white blood cells more efficiently. But, he adds, “I err on the side of safety.…I’m not an advocate of using St. John’s wort [an herbal antidepressant] with prescription antidepressants or kava [a relaxant] with anti-anxiety medications because we really don’t know what the mechanism of action is for those herbs. We’re getting an idea, but we don’t know yet.”