Tanakan

Tanakan, also known as Rokan, Tebonin, or LI 1370 (aka Kaveri) is a trade name for a pharmaceutical that was originally known as preparation EGb176 (which later became a trademarked name), an herbal preparation which is a standardized extract of Ginkgo biloba leaf, a tree native to China. It is also marketed non-medicinally as a dietary supplement under the trade names GinkGold, Ginkoba, and Quanterra. Its chief components are flavenoids 24% (quercetin, kaempferol and isorhamnetin or tamarixetin) and terpenoids 6% (ginkgolides and bilobalide specific to the Ginkgo tree). Other constituents include proanthocyanidins, glucose, rhamnose, organic acids, D-glucaric and ginkgolic acids. It has anti-oxidant, anti-inflammatory, vasodilator, and anti-coagulant properties, and modulating effects on the glutamatergic, cholinergic, dopaminergic and seratonergic (neurotransmitter) systems. It has been used as a treatment for dementia and supplementation as a memory enhancer.

Uses

Medicinal uses

Medicinal uses are based on the extract's vasodilation and anti-inflammatory properties.

Extracts as described below have been used for symptomatic treatment of mild to moderate cerebrovascular insufficiency (demential syndromes in primary degenerative dementia, vascular dementia, and mixed forms of both) with the following symptoms: memory deficit, disturbance in concentration, depressive emotional condition, dizziness, tinnitus, and headache (1, 3, 20–22).

Such extracts are also used to improve pain-free walking distance in people with peripheral arterial occlusive disease such as intermittent claudication, Raynaud disease, acrocyanosis, and post-phlebitis syndrome.

Other uses are to treat inner ear disorders such as tinnitus and vertigo of vascular and involutive origin (20, 23–27).

Dosage and administration

The supplement form of Gingko biloba is called Ginkgo biloba EGb-761 extract. It should be a 50:1 concentrated extract. Administration is orally by film coated tablet or liquid. Dosage forms are usually a 40 mg or 60 mg tablet or capsule or 1ml of 40 mg/ml liquid. Gingko biloba extract should be taken with meals.

Daily dosages less than 240 mg have not been shown to be clinically effective. There is some evidence that a single 240 mg dose is more effective than a split dose taken throughout the day, though part of the effect may be a higher rate of compliance with the regimen rather than physiologic effects.

Dietary supplement

Available dietary supplements mimic the medicinal form, and have been used for memory enhancement. For cognitive enhancement, take 120–240 mg, one to four hours before performance. To alleviate cognitive decline in older adults, take 40–120 mg, three times a day. There is no clinical evidence for enhancement of memory in non-memory-impaired subjects.

Traditional Chinese medicine

Preparations of the nuts, fruit and dried leaves have been used in traditional Chinese remedies for at least 2800 years, and as a clinical medicinal since the late 15th century. It was used in the treatment of asthma, bronchitis, and leukorrhea.

Adverse effects and drug interactions

Ginkgo Biloba Extract (GBE, referring to EGb 176) is considered to be safe and side effects are rare. In a few cases, gastrointestinal upset, headaches, skin reactions, and dizziness were reported.

• spontaneous bleeding - Because Ginkgo Biloba Extract (GBE) decreases platelet aggregation (stickiness), GBE can result in spontaneous bleeding, including intracranial hemorrhage
• GBE has not been proven safe for use during pregnancy and breastfeeding
• Because of its anti-thrombotic activity, ginkgo may increase bleeding risk during surgery.
• GBE may exacerbate bleeding disorders such as hemophilia, or increase risk of hemorrhagic stroke, especially those who smoke
• it may precipitate seizures in epileptic persons

GBE can have interactions with the following medications:

• Anticonvulsant medications: High doses of Ginkgo biloba could decrease the effectiveness of anticonvulsant therapy in patients taking carbamazepine or valproic acid to control seizures.
• Blood-thinning medications: Ginkgo has blood-thinning properties and may potentiate anticoagulant (blood-thinning) medications, such as aspirin, clopidogrel, dipyridamole, heparin, ticlopidine, or warfarin.
• Cylosporine: GBE may be beneficial during treatment with cyclosporine because of its ability to protect cell membranes from damage.
• Monoamine oxidase inhibitors (MAOIs): GBE may enhance the effects (both good and bad) of antidepressant medications known as MAOIs, such as phenelzine and tranylcypromine.
• Papaverine: The combination of papaverine and GBE may be effective for the treatment of erectile dysfunction in patients who do not respond to papaverine alone.
• Thiazide diuretics: Although there has been one literature report of increased blood pressure associated with the use of ginkgo during treatment with thiazide diuretics, this interaction has not been verified by clinical trials
• Trazodone: Additionally, there has been a report of an adverse interaction between ginkgo and trazodone, an antidepressant medication, that resulted in an elderly patient going into a coma

Chemical and physical properties

Flavonol Glycosides 24%,Terpene Lactones 6%, Ginkgolic acid not more than 1~5ppm.

100% water-soluble fine light yellow powder, #80 mesh bulk density 0.50~0.65g/ml.

Preparation

35:1 to 67:1 dry concentration (average 50:1) via acetone-water extraction. The extract is standardized to 24% flavenoids, 6% terpenoids and less than 5 ppm of ginkgolic acid, a poison. The German Commission E monograph, Trockenextrakt (35–67: 1) aus Ginkgo-biloba- Blättern Extrakt mit Aceton-Wasser (Dry extract (35-67:1) of Ginkgo biloba - process of extraction with acetone-water). Bundesanzeiger, 1994, sets the standard for preparation of this extract. The scientific literature does not support the clinical benefits of other dosage forms of crude ginkgo leaf or low-concentration extracts made from the leaf, in particular ones using an ethanol-water or methanol-water extraction process.

Pharmacology

The terpene trilactones (TTL) and the flavonoids of GBE are responsible for the main pharmacological effects of the extract.

Both the acute and the chronic toxicity of an extract as specified under Description is very low; accordingly, the LD50 in the mouse was 7725 mg/kg body weight after oral application and 1100 mg/kg body weight after intravenous application.

Regulatory status

Ginkgo is one of the most commonly prescribed medications in Europe. It is approved for medicinal use in approximately 60 countries outside the United States, mostly in Europe and Asia. It is available as a dietary supplement without prescription in the United States, Canada and the U.K. In the U.S., under the 1994 Dietary Supplement Health and Education Act (DSHEA), the sale of Ginkgo biloba is regulated by the U.S. Food and Drug Administration (FDA) as a dietary supplement.

History

The ginkgo or maidenhair tree is one of the oldest species of trees in the world, dating to the mesozoic era 150 million years ago. Ginkgo seeds have been used in traditional Chinese medicine for at least 2800 years, and cooked seeds are occasionally eaten. Historically, ginkgo leaf extract has been used to treat a variety of ailments and conditions, including asthma, bronchitis, fatigue, and tinnitus (ringing or roaring sounds in the ears). The leaf has been recommended for medicinal uses as early as 1509 and is still used in the form of teas. German pharmaceutical company Dr. Willmar Schwabe GmbH & Co. launched its first ginkgo product, an extract formally called EGb 761, in 1977. Studies had shown that ginkgo was effective at increasing blood flow, so Schwabe marketed EGb 761, known commercially as Tebonin or Rokan, as a prescription medicine for the treatment of minor circulatory ailments. In 1988 alone, West German doctors wrote 5.24 million prescriptions for EGb 761 products. It has been available in Europe as a herbal extract since the early 1990s.

Research

Tinnitus and hearing loss

There is evidence of limited benefit in the reduction of tinnitus, both as a primary symptom and concommitant symptom of hearing loss.

Antidementia agent

In two large randomized controlled clinical trials, Ginkgo Biloba Extract failed to slow decline of cognitive function in elderly persons.

Sexual dysfunction

GBE has been studied as a remedy for SSRI-induced sexual dysfunction.

See also

• Chinese herbology

Further reading

• A comprehensive, almost exhaustive, 401 page book reviewing the chemistry, pharmacology, toxicology, and all clinical studies conducted on EGb761 in various areas of clinical application has been published. DeFeudis, F. V. (1998). Ginkgo biloba extract (EGB 761): From chemistry to the clinic. Wesbaden: Ullstein Medical. ISBN 9783861261735