BACKGROUND: Intermittent claudication is a painful symptom of peripheral arterial disease. Nonsurgical treatment consists of modification of lifestyle risk factors (quit smoking, lower cholesterol levels), regular physical exercise, and a variety of medications. The clinical effectiveness of these interventions has usually been modest. Gingko biloba, a commonly used medicinal herb, has active ingredients that inhibit platelets and potentially decrease red blood cell aggregation. Because of these actions, it has been tested for intermittent claudication. Although some controlled studies have suggested benefit, the results have been inconclusive. The authors performed a meta-analysis to better summarize the current evidence.
POPULATION STUDIED: A total of 415 patients were included in this analysis. Their demographic information was not provided.
STUDY DESIGN AND VALIDITY: This was a meta-analysis of the existing literature. Manuscripts were identified for inclusion through a systematic search of 6 appropriate databases, contacting manufacturers of the product for published and unpublished literature, and contacting authors for additional data. Eight randomized controlled trials (RCTs) were identified that compared gingko with placebo and included an assessment of walking distance. Two researchers independently reviewed each study, grading them on quality (randomization strategy, description of withdrawals and dropouts, blinding protocol) and extracting information on pain-free walking distance. Appropriate statistical tools were used to find the pooled difference in pain-free walking distance between gingko and placebo.
OUTCOMES MEASURED: The primary outcome studied was pain-free walking distance. Seven of the 8 studies also reported maximal walking distance at baseline and after randomization to gingko or placebo. Three of the 8 studies used the same standardized assessment of treadmill walking that included ergometer speed of 3 km per hour on a grade of 12%.
RESULTS: Six of the 8 RCTs had a quality score of at least 4 on a scale of 1 to 5. Seven of the studies showed that gingko was more effective than placebo; however, only 4 of those studies were statistically significant. When all 8 studies were pooled, gingko increased pain-free walking distance by 34 meters (95% confidence interval, 26-43 m) more than placebo. When the authors pooled different subsets of articles, similar results were found. Side effects of gingko were not reported in 3 of the studies. In the remaining 5 studies, the primary side effects were abdominal complaints, nausea, and dyspepsia, although the rates were not given.
Gingko biloba extract (120 or 160 mg a day) for 24 weeks improves pain-free walking distance by 37 yards when compared with placebo. This improvement is similar to other medications used for intermittent claudication that cost at least twice as much. Gingko biloba may be an effective adjunct to smoking cessation and a walking program for intermittent claudication.