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Ginkgo Meta-analysis
Confirms Efficacy in Peripheral Arterial Disease
A recent meta-analysis of controlled clinical
trials concluded that ginkgo leaf extract (Ginkgo biloba
L., Ginkgoaceae) is significantly more effective than placebo
in the treatment of the circulatory disorder known as intermittent
claudication (Pittler et al., 2000). The results of this
study support those of an earlier German meta-analysis of five
studies involving 174 subjects (Schneider, 1992).
Intermittent claudication, caused by a
buildup of atherosclerotic deposits in the blood vessels of the
limbs, is an early symptom of peripheral arterial disease. Claudication
(limping) occurs when narrowing of the arteries restricts the
flow of blood and oxygen to the leg muscles, causing calf pain
and subsequent difficulty in walking. The condition primarily
affects older people, and treatment options are limited. Walking
is probably the most effective treatment of all, but many patients
have difficulty adhering to the recommended exercise program.
For their meta-analysis, the investigators
identified eight randomized, placebo-controlled, double blind
studies that involved a total of 415 participants. All of the
studies used pain-free walking distance as the primary outcome
measure. In five of the eight trials, the investigators used a
daily dosage of 120 mg standardized ginkgo extract, and three
a daily dosage of 160 mg. Seven of the trials utilized EGb 761,
a concentrated ginkgo extract standardized to 24 percent ginkgo
flavone glycosides and 6 percent terpene lactones (W. Schwabe,
Karlsruhe, Germany). The majority of trials lasted 24 weeks, with
the exception of one six-week and one 12-week study.
Statistical pooling of results from the
eight trials showed that compared to placebo, ginkgo significantly
increased pain-free walking distance. The weighted mean difference
in walking distance between the gingko and placebo groups was
34 meters (approximately 100 feet). No adverse effects were reported
in three trials, which represented nearly half of the total number
of participants studied. In the other five trials, stomach upset
(including nausea and indigestion) was the most frequently reported
adverse event.
The authors concluded, "...this meta-analysis
suggests that oral medication with Ginkgo biloba extract
prolongs the pain-free (and maximal) walking distance in patients
with intermittent claudication." However, they cautioned, "The
overall effect seems modest, and several caveats about the available
trials prevent a final judgment on the efficacy of this treatment."
On the other hand, they also acknowledged the limitations of currently
available drug treatments for the condition. Pentoxifylline, one
drug approved in the U.S. for intermittent claudication, has "modest"
clinical effects and can cause serious adverse effects, including
cardiac arrhythmias and bleeding. The drug also costs significantly
more than ginkgo extract. In the U.S., the cost of a 120 mg daily
dose of ginkgo ranges from 41 to 84 cents. In comparison, a daily
dose of pentoxifylline (1200 mg) costs $1.83 to $1.93.
- Evelyn Leigh, Herb Research Foundation
[Pittler MH, Ernst E. Ginkgo biloba extract for the
treatment of intermittent claudication: A meta-analysis of randomized
trials. The American Journal of Medicine 2000; 108: 276-281.
Schneider B. Ginkgo biloba Extrakt bei peripheren arteriellen
Verschlusskrankeheiten (German with English summary). Arzneimittelforschung
1992; 42(1): 428-436.]
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