STANFORD RESEARCHERS STUDY GINKGO BILOBA'S EFFECTS ON PERIPHERAL ARTERY DISEASE

STANFORD, Calif. - In Europe, doctors commonly prescribe ginkgo biloba supplements to patients who have peripheral artery disease - a narrowing of arteries due to cholesterol buildup. Here in the United States, ginkgo biloba supplements are among the most popular on the market with consumers spending upward of $240 million on the herbal products in 1997 alone. But whether it really helps treat peripheral artery disease remains an open question.

For the next three years, John Farquhar, MD, professor of medicine emeritus, and Christopher Gardner, PhD, assistant research professor of medicine, will ponder this question at the Stanford Center for Research in Disease Prevention. The National Institutes of Health has granted them more than $1 million to tackle the question in a large-scale clinical study of ginkgo biloba. The researchers at Stanford's School of Medicine are now looking for study volunteers who suffer from leg discomfort caused by peripheral artery disease.

'Many with peripheral artery disease are surprisingly unaware of the impairment of their arteries. Only about one- quarter have clear-cut pain when walking.' Gardner said. 'The main goal of this study is to find out if people who take ginkgo will be able to increase the distance they are able to walk free of pain or discomfort.'

Volunteers shouldn't be hard to find. Peripheral artery disease affects about 14 percent of Americans over age 50. The disease has a predilection for people with diabetes, high blood pressure or heart disease and those who smoke, and it's just as likely to strike women as men. In later stages, patients may have a stroke caused by blood clots.

Walking is often considered among the best self-help treatment for the millions of Americans with the disease, but for those with advanced artery narrowing, walking for even short periods can lead to debilitating pain.

The researchers are looking for 72 patients for the four-month trial, which starts in late July. Because the researchers have more than a year to find and enroll these participants, the start date for volunteers is flexible. Volunteers will be randomly given ginkgo biloba or placebos. Then they will have to stop by the research center at Stanford Hospital & Clinics four times to have their blood drawn and to walk on a treadmill.

The researchers use some simple tests to screen volunteers for peripheral artery disease. One is a comparison of a volunteer's arm and leg blood pressure. If the ratio of the two blood pressures suggests impaired blood flow in the legs, the volunteer will be scheduled for a second test.

The second test requires two visits on separate days. 'To qualify, volunteers need to be capable of walking for at least one, but fewer than 12 minutes on a treadmill before their leg pain makes it impossible for them to continue,' Gardner said. 'The catch is that the treadmill incline goes higher and higher every two minutes.'

Volunteers who exceed the 12-minute point cannot participate in the main trial, but they can still contribute to the study. Gardner and his colleagues are curious whether ginkgo biloba has an effect when combined with aspirin, so they have created a one-month, 60-person study to explore that question.

Aspirin, a blood thinner, treats the disease by reducing the risk of blood clots. Some peripheral artery disease sufferers regularly take aspirin with ginkgo biloba. Preliminary results suggest that taking the two together presents no problems, but researchers want to be more certain of this. Gardner said the scientists expect that most of the participants in the trial will already be taking aspirin because it's considered standard treatment for peripheral artery disease.

Those interested in learning more about the study and possibly participating can contact study coordinator Joel Nicholus at (650) 723-7022.