"Medicinal uses

Extracts of Ginkgo leaves contain flavonoid glycosides and terpenoids (ginkgolides, bilobalides) and have been used pharmaceutically. Ginkgo supplements are usually taken in the range of 40–200 mg per day. Recently, careful clinical trials have shown Ginkgo to be effective in treating dementia^[30] but not preventing the onset of Alzheimer's Disease in normal people....^[31][32]"

Is There a Risk of Bleeding Associated with Standardized Ginkgo biloba Extract Therapy?

"Study Objective. To determine the effect of standardized Ginkgo biloba leaf extracts (GBE) on outcome parameters of hemostasis associated with risk of bleeding...

Measurements and Main Results. The MEDLINE, EMBASE, Cochrane Library, and SciSearch databases were searched from inception through 2009. The following outcome parameters of hemostasis were assessed: blood flow, blood viscosity, adenosine 5′-diphosphate (ADP)-induced platelet aggregation, fibrinogen concentration, activated partial thromboplastin time (aPTT), and prothrombin time (PT). Reference parameter values were taken into account when assessing clinical relevance of statistically significant treatment effects...

Conclusion. Based on meta-analysis of hemostasis outcomes, comparison of mean difference or baseline change between treatment and placebo groups did not indicate a higher bleeding risk associated with standardized GBE. This finding ultimately contributes to an informed evaluation of GBE use, including patient self-medication...

Discussion

To our knowledge, this is the first metaanalysis to investigate the effects of GBE on blood perfusion, platelet function, and coagulation, and thus all phases of primary and secondary hemostasis. The meta-analysis showed a positive effect of GBE on blood perfusion as reduced blood viscosity, but no evidence of any effect on measures of platelet function (ADP-induced platelet aggregation) and coagulation (fibrinogen concentration, aPTT, PT). Subgroup analyses did not show a statistically significant difference in PT, but did show a statistically significant, but not clinically relevant, reduction in aPTT for subgroups receiving highdose GBE and for studies including only patients (not healthy volunteers).

The analyses did not indicate a higher risk of bleeding associated with standardized GBE. The significant and clinically relevant effect observed for blood viscosity indicating a positive effect of GBE on blood perfusion support its use in peripheral artery occlusive disease, as well as tinnitus and vertigo of vascular origin. Blood viscosity depends on various physiologic factors such as blood cell deformability, but is not considered a major risk factor for spontaneous bleeding events.

Heterogeneity was present in most analyses: healthy volunteer and patient populations were considered in the included studies for fibrinogen concentration, resulting in heterogeneity among studies and in results with a wide range of both positive and negative values. For patients with diabetes or renal insufficiency, fibrinogen concentrations are typically elevated. Platelet aggregation might have been influenced by clinically relevant changes in platelet aggregation in some study participants, which would explain the large range of effects in these studies.

The analyses were strengthened by the availability of unpublished data on aPTT and PT from four GBE trials in patients with dementia that allowed the most thorough analyses to date. Even though GBE seemed to have a stronger effect on aPTT than on PT, clinically significant results indicating an increased risk of bleeding were not found in any of the included studies. One of the included studies^[36] investigated the coagulation factors individually that were summarized into aPTT and PT in the metaanalyses. None of the coagulation factors were affected by the use of GBE, and thus a scenario where the effects of the individual coagulation factors cancel each other out can be excluded...

Conclusion

On the basis of the available evidence on parameters of hemostasis, standardized dry extracts from Ginkgo biloba leafs do not increase risk of bleeding. This finding ultimately contributes to an informed evaluation of GBE use, including patient self-medication."

David Emerson

Introduction