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St. Johns Wort Interferes With Lifesaving Drugs

来源:www.webmd.com
摘要:St。John‘sWortInterferesWithLifesavingDrugsByDanielDeNoonWebMDMedicalNewsFeb。10,2000(Atlanta)--TheFDAonThursdaywarnedphysiciansthatSt。John‘swort,acommonlyusedherbalremedy,dangerouslyinte......

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St. John's Wort Interferes With Lifesaving Drugs

By Daniel DeNoon
WebMD Medical News

Feb. 10, 2000 (Atlanta) -- The FDA on Thursday warned physicians that St. John's wort, a commonly used herbal remedy, dangerously interferes with a long list of prescription drugs. The action comes after two reports in the British medical journal The Lancet linking the herb to heart-transplant rejection and to HIV drug failure.

The FDA warning goes far beyond these two drugs. Because the herb appears to interfere with the way the body processes many drugs, the FDA advises physicians against using St. John's wort (also known as Hypericum perforatum) with a long list of medications. These include a wide range of drugs used to treat conditions such as HIV infection, heart disease, seizure, high blood pressure, and cancer. They also affect oral contraceptives and drugs used to prevent transplant rejection. People taking any of these medications are advised to consult their physicians before using products containing St. John's wort.

Even more drugs may be affected. WebMD has learned that St. John's wort also appears to speed the action of an intestinal protein that clears drugs out of the body. One of these drugs is the heart drug digoxin. Inadequate levels of digoxin may lead to serious elevations in heart rate or inability of the drug to improve heart function.

Although the new studies -- and the FDA warning -- apply only to St. John's wort, Georg Noll, MD, co-author of one of the reports, tells WebMD that other herbal remedies may be far less safe than commonly assumed. "Many doctors and patients are not aware that these herbal drugs you can buy over the counter are dangerous, as they can interact with other medications," says Noll, a cardiologist at University Hospital in Zurich, Switzerland. "I tell patients they shouldn't take any over-the-counter drug without informing the treating doctor."

Stephen C. Piscitelli, PharmD, lead author of the other study, tells WebMD that there is a dark side to the benefits of these natural products. "I think it's clear that herbal remedies do have pharmacological effects, but clearly there can be dangers as well," he says. "No physician really asks about [St. John's wort] when they are doing a history, and patients assume that if it is an herbal remedy, it must be safe."

So-called nutritional supplements need not undergo the same FDA scrutiny as pharmaceutical drugs. The FDA warning about St. John's wort -- only the second to be issued for such an agent -- indicates that this soon may change. This would be very good news to Christopher McMullen, president of the Hypericum Buyers Club, the Los Angeles firm that sells the St. John's wort extracts used in the NIH study and, McMullen says, the only U.S. company to offer pharmaceutical-grade Hypericum extracts.

"Let's regulate this stuff and level the playing field so you know what you are getting," McMullen tells WebMD. "You go to the store and see five different products and the buyer doesn't know what is in the bottle. We like to sleep at night, so everything we share with our people has to be the best. Absolutely, I welcome regulation. There are charlatans out there."

Piscitelli and colleagues studied interactions between McMullen's Hypericum product and the HIV protease inhibitor Crixivan (indinavir). The researchers found that the level of indinavir dropped by 57-81% in all eight patients tested. "We didn't have the situation where four patients had an effect and four didn't. A reduction of this magnitude clearly could be associated with treatment failure," Piscitelli says.

For patients with HIV infection, such a failure would mean the development of drug-resistant forms of the virus, greatly limiting remaining treatment options. Noll and colleagues saw an even more potentially catastrophic development in a completely different patient population. They report two cases of acute heart-transplant rejection soon after the patients -- who took cyclosporine to prevent their immune systems from attacking their new organs -- began taking St. John's wort. Both patients had significantly decreased cyclosporine levels, but no other abnormalities. Both survived the episode and regained stable cyclosporine levels when they stopped taking the herbal extracts.

"The number of patients using St. John's wort is increasing day by day," Noll says. "They are informed by the press it is OK to treat mood disorder. In Europe, it is quite popular."

St. John's wort is commonly used in the U.S. and in Europe for self-medication to treat depression. It is an approved drug in Germany, where 3 million prescriptions are written each year -- 25 times the number of Prozac (fluoxetine) prescriptions. A 1999 study published in the British Medical Journal showed that the herb did improve symptoms of depression to the same extent as one of the older antidepressants, Tofranil (imipramine). Another study looking at the effectiveness of St. John's wort, funded by the National Institute of Mental Health, is underway at Duke University.

"As far as someone taking St. John's wort and not telling their doctor, that's going to be a problem," Edward T. Morgan, PhD, professor of pharmacology at Emory University in Atlanta, tells WebMD. "A lot of drugs are potentially affected ... there will be a lot of other factors to take into account."

 

作者: DanielDeNoon 2006-8-16
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