Mieke van Driel
This is the fourth article in a series providing evidence-based answers to common questions about complementary medicines from consumers and healthcare professionals.
What is ginkgo biloba?
Ginkgo biloba is extracted from the leaves of the maidenhair tree, which is native to China. The nuts from the tree are considered a delicacy in some countries but are known to be toxic when consumed in large quantities.1,2 The leaf extract has featured prominently in traditional Chinese medicine for thousands of years and has been thought to relieve a wide array of symptoms including memory loss, anxiety, asthma, schizophrenia, diabetes and erectile dysfunction.3 Ginkgo biloba has recently attracted attention for its possible effects on Alzheimer’s disease and dementia; however, research findings have been inconsistent and no firm conclusions can be drawn.4 Despite the lack of clear evidence for its benefits, it is widely used both in the East and the West.
Who asks about ginkgo biloba?
To identify the most commonly asked questions, we analysed 125,919 calls from the NPS MedicineWise (NPS) Medicines Line (1 September 2002–30 June 2010) for consumers and 57,840 calls from the Therapeutic Advice and Information Service (TAIS; 1 Jan 2000–30 June 2010) for community healthcare providers.5 The medicine call centres received queries from 353 consumers (3.5% of all complementary medicines questions) and 169 healthcare professionals (3.1%) concerning gingko biloba.5
The average age of consumers calling about ginkgo biloba was 58 years; 77% were women and most questions focused on interactions (58%), efficacy (17%) and adverse drug reactions (ADRs, 10.6%). Similarly, health professionals were predominantly concerned about interactions (69%) and ADRs (28%), whereas efficacy only featured in 3.6% of their calls.
Common consumer questions
Is ginkgo biloba effective for treating tinnitus?
No, ginkgo biloba is probably not effective for treating tinnitus. Ginkgo biloba has been widely used to manage tinnitus. The proposed mechanism of action is via effects on vasoregulation and neuronal metabolism. Several studies have suggested an effect on tinnitus caused by cerebrovascular insufficiency for up to 3 months.6 However, positive improvement was not shown in two large, high-quality studies where tinnitus was the primary complaint.7 The discrepancies in the literature may be related to the different causes of tinnitus.7
Is it safe to combine ginkgo biloba with antidepressants?
The limited information published suggests it is not considered safe to combine ginkgo biloba with antidepressants, including prescription medications such as selective serotonin re-uptake inhibitors, or St John’s wort.8–10 This topic has been poorly researched. However, studies in animals have suggested that taking ginkgo biloba and antidepressants together may increase the risk of serotonin toxicity.8 Symptoms of serotonin toxicity include confusion, sweating, shaking, muscle contraction and diarrhoea.11 However, studies in humans are lacking. There have also been reports of ginkgo biloba possibly causing seizures by reducing the levels of antiepileptic medication.9,10 Given that some antidepressants also increase the risk of seizures, the benefit of using a combination of ginkgo biloba and an antidepressant should be weighed against the potentially high risk of seizure.
Common health professional questions
Is it safe to combine blood pressure medication with ginkgo biloba?
It is considered safe to combine blood pressure medication with ginkgo biloba. However, blood pressure monitoring is recommended when a patient commences taking the herb.12–15 Ginkgo biloba has been shown to reduce blood pressure in some trials,16 although most studies did not report a change in blood pressure.12–15
Does ginkgo biloba interact with aspirin?
No, it is safe to combine ginkgo biloba with aspirin. Case reports have suggested that ginkgo biloba may increase the risk of bleeding17–19 but several randomised controlled trials have found that ginkgo biloba does not increase the risk of bleeding when added to aspirin at a dose of up to 500 mg/day.20–23
Sanne Kreijkamp-Kaspers MD, PhD, FRACGP, MSc, Senior Lecturer, Discipline of General Practice, School of Medicine, The University of Queensland, Brisbane, QLD. firstname.lastname@example.org
Treasure McGuire PhD, BPharm, BSc, GradDipClinHospPharm, GCHEd, Associate Professor; Faculty of Health & Medical Sciences, Bond University, Gold Coast; Senior Lecturer, School of Pharmacy, The University of Queensland, Brisbane; Assistant Director (Practice and Development), Mater Pharmacy Services, Mater Health Services, Brisbane, QLD
Suzanne Bedford PhD, BSc, Honorary Research Fellow at Mater Research Institute, The University of Queensland, Brisbane, QLD
Peter Loadsman BPharm, BSc, Mater Pharmacy Services, Mater Health Services, Brisbane, QLD
Marie Pirotta FRACGP, PhD, NHMRC Career Development Fellow, Department of General Practice, University of Melbourne, Carlton, VIC
Geraldine Moses BPharm, DClinPharm, Senior Clinical Pharmacist, Mater Pharmacy Services, Mater Health Services, Brisbane, QLD
Mieke van Driel MD, MSc, PhD, FRACGP, Professor and Head, Discipline of General Practice, School of Medicine, The University of Queensland, Brisbane, QLD
Competing interests: The authors received an Integrative Medicine grant from the RACGP.
Provenance and peer review: Commissioned, externally peer reviewed.
- Kajiyama Y, Fujii K, Takeuchi H, Manabe Y. Ginkgo seed poisoning. Pediatrics 2002;109:325–27.
- Hasegawa S, Oda Y, Ichiyama T, Hori Y, Furukawa S. Ginkgo nut intoxication in a 2-year-old male. Pediatr Neurol 2006;35:275–76.
- Natural Standard Professional Database. Available at www.naturaldatabase.com [Accessed 19 September 2013].
- Birks J, Grimley Evans J. Ginkgo biloba for cognitive impairment and dementia. Cochrane Database Syst Rev 2009;CD003120.
- Kreijkamp-Kaspers S, McGuire T, Bedford S, et al. Your questions about complementary medicines answered. Aust Fam Physician 2015;44:373–74.
- Holstein N. [ginkgo special extract EGB 761 in tinnitus therapy. An overview of results of completed clinical trials]. Fortschr Med Orig 2001;118:157–64.
- Hilton MP, Zimmermann EF, Hunt WT. Ginkgo biloba for tinnitus. Cochrane Database Syst Rev 2013;3:CD003852.
- Longpre F, Garneau P, Christen Y, Ramassamy C. Protection by EGB 761 against beta-amyloid-induced neurotoxicity: Involvement of nf-kappab, sirt1, and mapks pathways and inhibition of amyloid fibril formation. Free Radic Biol Med 2006;41:1781–94.
- Gregory PJ. Seizure associated with ginkgo biloba? Ann Intern Med 2001;134:344.
- Kupiec T, Raj V. Fatal seizures due to potential herb-drug interactions with Ginkgo biloba. J Anal Toxicol 2005;29:755–58.
- Rossi S. Australian Medicines Handbook 2013 Available at www.amh.net.au [Accessed 28 May 2014].
- Brinkley TE, Lovato JF, Arnold AM, et al. Effect of ginkgo biloba on blood pressure and incidence of hypertension in elderly men and women. Am J Hypertens 2010;23:528–33.
- Keheyan G, Dunn LA, Hall WL. Acute effects of ginkgo biloba extract on vascular function and blood pressure. Plant Foods Hum Nutr 2011;66:209–11.
- Mehlsen J, Drabaek H, Wiinberg N, Winther K. Effects of a ginkgo biloba extract on forearm haemodynamics in healthy volunteers. Clin Physiol Funct Imaging 2002;22:375–78.
- Kudolo GB, Wang W, Javors M, Blodgett J. The effect of the ingestion of ginkgo biloba extract (EGB 761) on the pharmacokinetics of metformin in non-diabetic and type 2 diabetic subjects--a double blind placebo-controlled, crossover study. Clin Nutr 2006;25:606–16.
- Kudolo GB. The effect of 3-month ingestion of ginkgo biloba extract on pancreatic beta-cell function in response to glucose loading in normal glucose tolerant individuals. J Clin Pharmacol 2000;40:647–54.
- Rosenblatt M, Mindel J. Spontaneous hyphema associated with ingestion of ginkgo biloba extract. N Engl J Med 1997;336:1108.
- Bebbington A, Kulkarni R, Roberts P. Ginkgo biloba: Persistent bleeding after total hip arthroplasty caused by herbal self-medication. J Arthroplasty 2005;20:125–26.
- Bent S, Goldberg H, Padula A, Avins AL. Spontaneous bleeding associated with ginkgo biloba: A case report and systematic review of the literature: A case report and systematic review of the literature. J Gen Intern Med 2005;20:657–61.
- Kuller LH, Ives DG, Fitzpatrick AL, et al. Does ginkgo biloba reduce the risk of cardiovascular events? Circ Cardiovasc Qual Outcomes 2010;3:41–47.
- Gardner CD, Zehnder JL, Rigby AJ, Nicholus JR, Farquhar JW. Effect of ginkgo biloba (EGB 761) and aspirin on platelet aggregation and platelet function analysis among older adults at risk of cardiovascular disease: A randomized clinical trial. Blood Coagul Fibrinolysis 2007;18:787–93.
- Wolf HR. Does ginkgo biloba special extract egb 761 provide additional effects on coagulation and bleeding when added to acetylsalicylic acid 500 mg daily? Drugs R D 2006;7:163–72.
- 23. Kohler S, Funk P, Kieser M. Influence of a 7-day treatment with ginkgo biloba special extract EGB 761 on bleeding time and coagulation: A randomized, placebo-controlled, double-blind study in healthy volunteers. Blood Coagul Fibrinolysis 2004;15:303–09.