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Aug. 31, 2001 -- Researchers studying pregnant women taking the herbal supplement ginkgo biloba have found traces of a substance in the placental blood that is known to be toxic in high doses and can even cause birth defects.
The amount of the substance, called colchicine, was far below the level that might cause harm. But the authors report that natural plant products could potentially cause problems if taken during pregnancy and that the risks need to be studied more closely. The investigators also suggest that women who are pregnant or trying to conceive should avoid taking such supplements.
The study appears in the September issue of Chemical Research in Toxicology.
Doctors know a lot about colchicine (pronounced KOL-cha-seen). They have used it to treat patients with gout for a long time. But they are not certain how trace amounts got into the pregnant women who were taking ginkgo biloba.
"The herb ginkgo does not contain colchicine, period," says Joseph M. Betz, PhD, vice president for scientific and technical affairs at the American Herbal Products Association in Silver Spring, Md. "Colchicine only appears in one plant family, the lily family," he continues. "If the researchers did find colchicine in supplements, it was a contaminant."
Betz says he wonders about the accuracy of the tests. It's possible that the researchers were tricked by a chemical imposter, one that looks like colchicine and showed up on the tests. That would mean that colchicine could have been reported by mistake, he says.
Senior author Shahriar Mobashery, PhD, supports his methods, however. He admits he's not an expert on the naturally occurring substances in ginkgo biloba. Nevertheless, "During pregnancy, women should be careful about the substances they eat and drink, including even coffee and tea, because caffeine and other alkaloids accumulate in the placenta," he says. Mobashery is a full professor of chemistry, biochemistry, and pharmacology at Wayne State University in Detroit.
Meanwhile, Michael Hirt, MD, a physician who prescribes herbal medicines every day to appropriate patients, agrees that pregnant women should be cautious about taking herbs. "Just because something's natural doesn't mean it's safe," he says. "You should think of herbal medicines as green drugs. They've been selected by herbalists over centuries because they have real physiological effects. A pregnant woman should take any medication, conventional or herbal, only when there are good reasons to do so."
Hirt is the director of the Center for Integrative Medicine at Encino-Tarzana Regional Medical Center in Los Angeles.
He recommends ginkgo to elderly folks who experience aching calves. "If your grandfather has trouble walking, ginkgo might increase blood flow to his legs, because clinical studies show it can help people with peripheral vascular disease. At the same time, it can also interfere with certain cardiac medications, so check with your doctor first."
Boris Petrikovsky, MD, PhD, also recommends being cautious. He is the chairman of obstetrics and gynecology at Nassau University Medical Center and is the co-author of What Your Unborn Baby Wants You to Know, A Complete Guide to a Healthy Pregnancy, which includes a chapter on herbal medicines.
"Herbal medicines have not been scrutinized as carefully as conventional medicines," Petrikovsky says. "Government agencies assure the safety of pharmaceuticals. This paper reminds us that herbal medicines can be potentially dangerous."