Ask Dr. Stephan Moll

These questions have been submitted by folks on the mailing list and answered by Dr. Moll, Director of the Thrombophilia Program at the Carolina Cardiovascular Biology Center, Department of Medicine, Division of Hematology-Oncology, UNC Chapel Hill (North Carolina, USA). Why am I doing this?

103. Ginkgo biloba

Q: "Last year I had a TIA (= transient ischemic attack = mini-stroke). My doctor, knowing I prefer to be without warfarin, put me on a graded dose of ginkgo biloba. I have been taking it ever since. So far so good. Apparently, some pharmaceutical company in France did a study on the properties of Ginkgo Biloba and came to the conclusion that it does improve circulation."

A: While ginkgo does have a positive effect on blood flow in arteries (reference 1), its effect in preventing stroke has not been examined. In a patient with true TIA I would NOT count on ginkgo being effective enough to prevent a future stroke. I would advise against the sole use of ginkgo. I would recommend the established standard treatment to the patient with TIA: aspirin.

Anatomy of Arteries and Veins: Arteries are the blood vessels through which the blood flows from the heart into the periphery: into the brain, the internal organs, the legs and the arms (figure 1). A clot in an artery leads to stroke, TIA (mini-stroke), heart attack, or peripheral arterial clot and gangrene (painful, cold, and pale digits or a whole extremity, later turning black). Veins are the blood vessels that carry blood back to the heart (figure 2). A clot in the deep veins of legs, arms, abdomen or around the brain is called deep vein thrombosis (DVT). If a piece of clot from a leg or arm DVT breaks off it can travel into the lung, causing a pulmonary embolism (PE).

FIGURE 1

FIGURE 2

Blood clots are made up of little particles called platelets and a meshwork of protein strands, called fibrin. Clots in arteries have a different composition than clots in veins. Clots in arteries are mostly made up of platelets (figure 3); clots in veins mostly made up of fibrin (figure 4). Platelets are made slick and prevented from sticking together to form a clot by aspirin, Plavix®, Aggrenox®, Ibuprofen and a whole variety of so-called NSAIDs (non-steroidal anti-inflammatory drugs). Since platelets are the ones that mostly cause the clots in arteries, aspirin and these drugs are good to prevent clots in arteries. Since platelets do not play much of a role in the clots in veins, aspirin is not very (if at all) useful to prevent clots in veins, such as DVT and PE. Heparin and warfarin are good in preventing fibrin from forming. They are, therefore, very effective drugs in preventing blood clot sin veins from forming. Since fibrin also plays some role in clot formation in arteries, heparin and warfarin are also useful drugs in preventing artery clots. However, they cause more bleeding than aspirin and are, therefore, not the first choice in preventing artery clots.

* not clear whether it has any effect in humans protecting from blood clots. See www.fvleiden.org/ask/70.html

LMWH = low molecular weight heparins; in red the main drugs used; in gray the drugs that are also effective, but not the first choice of treatment.

Ginkgo has been shown to improve symptoms of impaired arterial circulation: In patients with hardening of the arteries of the legs (= arteriosclerosis) patients treated with ginkgo can walk farther without pain than patients treated with placebo (reference 1). However, Ginkgo has not been compared in efficacy to aspirin or any other pharmaceutical anti-platelet agent, such as Plavix®, Tiklyd®, or Aggrenox®. Up to this point there are no published studies of the use of Ginkgo in the treatment or prevention of stroke. I would not count on it having sufficient effect to prevent stroke or heart attacks. I would clearly not recommend it as sole treatment for a TIA.

An ongoing clinical trial is examining the efficacy of Ginkgo biloba (Tanakan®) in people with a history of stroke: it is being examined whether Tanakan® helps patients recover faster or more completely from a stroke if they use Tanakan® in addition to aspirin. It is important to note, however, that Tanakan® is given together with aspirin in this study, not as a sole treatment (www.clinicaltrials.gov/ct/show/NCT00276380). Results of this study are not yet available.

References:

1. Horsch S et al. Ginkgo biloba special extract EGb 761 in the treatment of peripheral arterial occlusive disease (PAOD)--a review based on randomized, controlled studies. Int J Clin Pharmacol Ther. 2004 Feb;42:63-72

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