Introduction
Ginkgo biloba is a botanical supplement derived from the leaves of the Ginkgo biloba tree, one of the oldest living tree species. While not FDA-approved as a drug, it is widely used as a dietary supplement with purported medicinal properties. Standardized extracts (EGb 761) contain 24% flavonoid glycosides and 6% terpene lactones, which are believed to contribute to its pharmacological effects.
Mechanism of Action
Ginkgo biloba exhibits multiple pharmacological activities:
- Vasoregulatory effects: Improves peripheral and cerebral blood flow through modulation of endothelial-derived relaxing factor
- Antioxidant properties: Scavenges free radicals and reduces oxidative stress
- Platelet-activating factor (PAF) inhibition: Ginkgolides competitively inhibit PAF receptors
- Neuroprotective effects: Modulates neurotransmitter systems and reduces neuronal apoptosis
- Mitochondrial protection: Enhances mitochondrial respiration and ATP production
Indications
FDA-approved indications: None (classified as dietary supplement) Common off-label uses:- Cognitive enhancement (mild cognitive impairment)
- Dementia symptoms (Alzheimer's disease and vascular dementia)
- Peripheral arterial disease (intermittent claudication)
- Tinnitus of vascular origin
- Vertigo and dizziness
- Age-related macular degeneration (investigational)
Dosage and Administration
Standard dosing: 120-240 mg daily of standardized extract (EGb 761) in divided doses Administration:- Typically administered orally
- Should be taken with food to minimize gastrointestinal upset
- Treatment duration: Minimum 4-8 weeks for observable effects
- Elderly: No dosage adjustment required
- Renal impairment: Use with caution
- Hepatic impairment: Use with caution
- Pediatrics: Not recommended due to insufficient safety data
Pharmacokinetics
Absorption: Flavonoids and terpenoids are absorbed in the small intestine Distribution: Widely distributed; crosses blood-brain barrier Metabolism: Hepatic metabolism via phase II conjugation Elimination: Primarily renal excretion; elimination half-life approximately 4-6 hours Bioavailability: Approximately 80% for active constituentsContraindications
- Hypersensitivity to Ginkgo biloba or its components
- Patients with bleeding disorders
- Concomitant use with anticoagulants/antiplatelets (relative contraindication)
- Pregnancy and breastfeeding (due to insufficient safety data)
- Preoperative period (discontinue 2 weeks before surgery)
Warnings and Precautions
- Bleeding risk: May inhibit platelet aggregation; monitor for bleeding signs
- Seizures: Contains ginkgotoxin (4'-O-methylpyridoxine) which may lower seizure threshold
- Diabetes: May alter insulin secretion and metabolism
- Fertility effects: Potential impact on reproductive hormones
- Allergic reactions: May cause dermatitis in sensitive individuals
Drug Interactions
Major interactions:- Anticoagulants (warfarin, heparin): Increased bleeding risk
- Antiplatelets (aspirin, clopidogrel): Enhanced antiplatelet effects
- NSAIDs: Potentiated bleeding risk
- SSRIs: Possible serotonin syndrome
- Anticonvulsants: Altered seizure threshold
- Antihypertensives: Additive hypotensive effects
- Hypoglycemics: Enhanced glucose-lowering effects
- CYP2C19 substrates: Potential inhibition
Adverse Effects
Common (≥1%):- Headache
- Gastrointestinal discomfort
- Dizziness
- Allergic skin reactions
- Bleeding (cerebral, retinal, gastrointestinal)
- Seizures
- Severe allergic reactions
- Stevens-Johnson syndrome (rare)
Monitoring Parameters
- Bleeding time and coagulation parameters in high-risk patients
- Cognitive assessment in dementia patients
- Neurological status in seizure-prone individuals
- Blood glucose levels in diabetics
- Liver function tests with long-term use
- Signs of allergic reactions
Patient Education
- Inform healthcare providers about all supplements being taken
- Discontinue 2 weeks before surgical procedures
- Report any signs of bleeding (unusual bruising, blood in stool)
- Be aware of potential interactions with prescription medications
- Purchase from reputable sources to ensure product quality
- Understand that effects may take several weeks to manifest
- Do not use during pregnancy or breastfeeding without medical consultation
References
1. DeKosky ST, et al. JAMA. 2008;300(19):2253-2262. 2. Birks J, Grimley Evans J. Cochrane Database Syst Rev. 2009;(1):CD003120. 3. Nicolaï SP, et al. Cochrane Database Syst Rev. 2013;(6):CD006888. 4. Hilton MP, Stuart EL. Cochrane Database Syst Rev. 2004;(2):CD003852. 5. Ude C, et al. Planta Med. 2013;79(13):1125-1132. 6. Natural Medicines Comprehensive Database. Ginkgo. 2023. 7. World Health Organization. Monographs on Selected Medicinal Plants. 1999.
Note: This information is for educational purposes only and should not replace professional medical advice. Patients should consult healthcare providers before starting any new supplement regimen.