Ginkgo Biloba Leaf Extract

Dry extract (35 - 67:1) from Ginkgo biloba L.  leaf [Fam.  Ginkgoaceae], extracted with acetone/water.  Active Ingredient Classification ASK No.  05939.  

A dry extract from the dried leaf of Ginkgo biloba L.  manufactured using acetone/water and subsequent purification steps without addition of concentrates or isolated ingredients.  

The drug/extract ratio is 35 - 67:1, on average 50:1.  

The extract is characterized by:

22 - 27 percent flavonone glycosides, determined as quercetin and kaempferol, including isorhamnetin (via HPLC) and calculated as flavones with a molar mass of MMr = 756.7 (quercetin glycosides) and Mr = 740.7 (kaempferol glycosides); 5 - 7 percent terpene lactones, of which approximately 2.8 - 3.4 percent consists of ginkgolides A, B, and C, as well as approximately 2.6 - 3.2 percent bilobalide; below 5 ppm ginkgolic acids.  

The given ranges include manufacturing and analytical variances.  

Pharmacological Properties, Pharmacokinetics, Toxicology

The following pharmacological effects have been established experimentally:

• Improvement of hypoxic tolerance, particularly in the cerebral tissue.  
• Inhibition of the development of traumatically or toxically induced cerebral edema, and acceleration of its regression.  
• Reduction of retinal edema and of cellular lesions in the retina.  
• Inhibition in age-related reduction of muscarinergic cholinoceptors and 2-adrenoceptors as well as stimulation of choline uptake in the hippocampus.  
• Increased memory performance and learning capacity.  
• Improvement in the compensation of disturbed equilibrium.  
• Improvement of blood flow, particularly in the region of microcirculation.  
• Improvement of the rheological properties of the blood.  
• Inactivation of toxic oxygen radicals (flavonoids).  
• Antagonism of the platelet-activating factor/PAF (ginkgolides).  
• Neuroprotective effect (ginkgolides A and B, bilobalide).  

The pharmacokinetics have been investigated both in animal experiments and in trials involving humans.  An absorption rate of 60 percent was found in rats for a radioactively labeled extract (as specified under Composition of Drug).  In humans after application of an extract specified as above, absolute bioavailability was 98 - 100 percent for ginkgolide A, 79 - 93 percent for ginkgolide B and at least 70 percent for bilobalide.  

Both the acute and the chronic toxicity of an extract as specified under Composition of Drug is very low; accordingly, the LD₅₀in the mouse was 7725 mg/kg body weight after oral application and 1100 mg/kg body weight after intravenous application.  

Investigations with this extract as specified above showed no effects which were either mutagenic, carcinogenic, or toxic to reproduction.  

No evaluation was performed on the transferability of the experimental results to extracts other than those investigated.  

[Ed.note:This statement refers to the fact that only a few proprietary ginkgo extracts were used in the studies upon which this monograph is based.  Whether these results can be extrapolated to other ginkgo extracts is uncertain.  SeeIntroduction]

Clinical Data

Uses

(a) For symptomatic treatment of disturbed performance in organic brain syndrome within the regimen of a therapeutic concept in cases of demential syndromes with the following principal symptoms:

Memory deficits, disturbances in concentration, depressive emotional condition, dizziness, tinnitus, and headache.  

The primary target groups are dementia syndromes, including primary degenerative dementia, vascular dementia, and mixed forms of both.  

Note: Prior to starting treatment with ginkgo extract, clarification should be obtained as to whether the pathological symptoms encountered are not based on an underlying disease requiring a specific treatment.  

(b) Improvement of pain-free walking distance in peripheral arterial occlusive disease in Stage II of Fontaine (intermittent claudication) in a regimen of physical therapeutic measures, in particular walking exercise.  

(c) Vertigo and tinnitus (ringing in the ear) of vascular and involutional origin.  

Contraindications

Hypersensitivity to Ginkgo biloba preparations.  

Side Effects

Very seldom stomach or intestinal upsets, headaches, or allergic skin reaction.  

None known.  

No restrictions known.  

None known.  

Unless otherwise prescribed:

Daily dosages:

Indication (a):

• 120 - 240 mg native dry extract in 2 or 3 doses.  

Indications (b) and (c):

• 120 - 160 mg native dry extract in 2 or 3 doses.  

In liquid or solid pharmaceutical forms, for oral intake.  

Indication (a):

• Length of administration should be judged according to the severity of symptoms and should extend at least 8 weeks in the case of chronic illness.  

Administration for more than 3 months should be reviewed as to justification for continued administration.  

Indication (b):

• Improvement of ambulatory range requires administration for not less than 6 weeks.  

Indication (c):

• Administration for more than 6 - 8 weeks has no therapeutic benefit.  

None known.  

None.  

None known.