Magnitude of Effect and Special Approach to Ginkgo biloba Extract EGb 761® in Cognitive Disorders

Abstract

In the early 70 s, improvements in methodical procedures of extraction and standardization of ginkgo preparation allowed the production of a highly concentrated and stable extract (EGb 761®) (definition see editorial) by the company Dr. Willmar Schwabe, which could be systematically tested in scientific programs. Consequently, numerous studies have been undertaken and provided replicable outcomes to demonstrate its efficacy in human population. EGb 761® is currently registered as an ethical drug in more than 50 countries around the world, and is prescribed for a range of neurological and vascular disorders including dementia, arterial occlusive disease, retinal deficit, and tinnitus. The following chapter will focus on the relevant data that support EGb 761® efficacy in the treatment of cognitive disorders in general, and dementia in particular. Besides the published data, the author will provide original results unveiling different factors that could interfere with EGb 761® efficacy and may be the source of the variations observed among studies in the EGb 761® literature. In the author’s opinion, such factors should be taken into consideration when implementing the design of future research and optimizing individual EGb 761® response in the clinical practice. Within the framework of this new approach, the author will not only answer the question as to whether EGb 761® works over placebo in cognitive disorders, but also attempt to estimate how well it works in particular conditions.

References

• 1 Clostre F. Ginkgo biloba extract (EGb 761®). State of knowledge in the dawn of the year 2000.  Ann Pharm Fr. 1999;  57 1S8-1S88
• 2 Cockle S M, Kimber S, Hindmarch I. The Effect of Ginkgo biloba Extract (LI 1370) Supplementation on Activities of Daily Living in Free Living Older Volunteers: A Questionnaire Survey.  Hum Psychopharmacol Clin Exp. 2000;  15 227-235
• 3 Cohen J. Statistical Power Analysis for the Behavioral Sciences, 2nd ed. Academic Press 1988
• 4 Curtis-Prior P, Vere D, Fray P. Therapeutic value of Ginkgo biloba in reducing symptoms of decline in mental function.  J Pharm Pharmacol. 1999;  51(5) 535-541
• 5 Diamond B J, Shiflett S C, Feiwel N, Matheis R J, Noskin O, Richards J A, Schoeberger N E. Ginkgo biloba extract: mechanisms and clinical indications.  Arch Phys Med Rehab. 2000;  81 668-678
• 6 Hofferberth B. The efficacy of EGb 761® in patients with senile dementia of the Alzheimer type, a double-blind, placebo-controlled study on different levels of investigation.  Human Psychopharmacol. 1994;  9 215-222
• 7 Kanowski S, Herrmann W M, Stephan K, Wierich W, Hörr R. Proof of Efficacy of the Ginkgo biloba Special Extract EGb 761® in Outpatients Suffering from Mild to Moderate Primary Degenerative Dementia of the Alzheimer Type or Multi-Infarct Dementia.  Pharmacopsychiatry. 1996;  29 47-56
• 8 Kanowski S, Hoerr R. Ginkgo biloba extract EGb 761® in dementia: Intent-to-treat analysis of 24-week, multicenter, double-blind, placebo controlled, randomized trial(in Press). 
• 9 Kidd P M. A review of nutrients and botanicals in the integrative management of cognitive dysfunction.  Altern Med Rev. 1999;  4 144-161
• 10 Kleijnen J, Knipschild P. Ginkgo biloba for cerebral insufficiency.  Br J Clin Pharmacol. 1992;  34 52-358
• 11 Le Bars P l, Kastelan J. Efficacy and safety of a Ginkgo biloba extract.  Public Health Nutrition. 2000;  3(4A) 495-499
• 12 Le Bars P L, Katz M M, Berman N, Itil T M, Freedman A M, Schatzberg A F. A Placebo-Controlled, Double-Blind, Randomized Trial of an Extract of Ginkgo biloba for Dementia.  JAMA. 1997;  278 327-1332
• 13 Le Bars P L, Kieser M, Itil K Z. A 26-Week Analysis of a double-blind, Placebo-Controlled Trial of the Ginkgo biloba Extract EGb 761® in dementia.  Dement Geriatr Cogn Disord.. 2000;  11(4) 230-237
• 14 Le Bars P L, Velasco F M, Ferguson J M, Dessain E C, Kieser M, Hoerr R. Influence of the Severity of Cognitive Impairment on the Effect of the Ginkgo biloba Extract EGb 761® in Alzheimer’s Disease.  Neuropsychobiology. 2002;  45 19-26
• 15 Letzel H, Haan J, Feil W B. Nootropics: Efficacy and tolerability of products from three active substance classes.  J Drug Dev Clin Pract. 1996;  8 77-94
• 16 Maurer K, Ihl R, Dierks T, Frolich L. Clinical efficacy of Ginkgo biloba special extract EGb 761® in dementia of the Alzheimer type.  J Psychiat Res. 1997;  31(6) 645-655
• 17 Oken B S, Storzbach D M, Kaye J A. The efficacy of Ginkgo biloba on cognitive function in Alzheimer disease.  Arch Neurol. 1998;  55(11) 1409-1415
• 18 Rigney U, Kimber S, Hindmarch I. The effect of acute doses of standardized ginkgo biloba extract on memory and psychomotor performance in volunteers.  Phytother Res. 1999;  13 408-415.
• 19 Soholm B. Clinical improvement of memory and other cognitive functions by Ginkgo biloba: Review of relevant literature.  Ad Natural Ther. 1998;  15 54-65
• 20 Stern R G, Mohs R C, Davidson M, Schmeidler J, Silverman J, Kramer-Ginsberg E, Searcey T, Bierer L, Davis K L. A Longitudinal Study of Alzheimer’s Disease: Measurement, Rate, and Predictors of Cognitive Deterioration.  Am J Psychiatry. 1994;  151 390-396
• 21 Wettsein A. Cholinesterase inhibitors and Ginkgo extracts-are they comparable in the treatment of dementia? Comparison of published placebo-controlled efficacy studies of at least six months’ duration.  Phytomedicine. 2000;  6(6) 393-401