ginkgo (generic name)
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Interactions with Drugs
Overall, controlled trials of ginkgo report few adverse effects and good tolerance, with rates of complications similar to placebo. However, use of ginkgo with drugs that may cause bleeding may further increase the risk of bleeding, based on multiple case reports of spontaneous bleeding in patients using ginkgo alone, with warfarin (Coumadin®), or with aspirin. One case report documents a possible increase in bleeding risk with ticlodipine (Ticlid®) and ginkgo. Examples of drugs that may increase the risk of bleeding include aspirin, anticoagulants ("blood thinners") such as warfarin (Coumadin®) or heparin, anti-platelet drugs such as clopidogrel (Plavix®), and non-steroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®). However, not all studies agree with the existence of this risk, and it is not clear if particular types of patients may be at greater risk.
Based on preliminary research, ginkgo may affect insulin and blood sugar levels. Caution is advised when using medications that may also lower blood sugar. Patients taking drugs for diabetes by mouth or insulin should be monitored closely by a qualified healthcare professional. Medication adjustments may be necessary.
Ginkgo has been found to decrease blood pressure in healthy volunteers, although some studies disagree. Theoretically, ginkgo may add to the effects of medications that also lower blood pressure, although raised blood pressure has been reported in a patient taking a thiazide diuretic ("water pill") with ginkgo. It has been suggested that Ginkgo biloba leaf extract (GBE) and nifedipine should not be ingested at the same time.
Monoamine oxidase (MAO) inhibition by ginkgo was reported in one animal study, but has not been confirmed in humans. In theory, if taken with MAOI drugs, such as isocarboxazid (Marplan®), phenelzine (Nardil®), or tranylcypromine (Parnate®), additive effects and side effects may occur. Based on laboratory research, ginkgo may also add to the effects of SSRI antidepressants such as sertraline (Zoloft®), with an increased risk of causing serotonin syndrome, a condition characterized by stiff muscles, fast heart rate, hyperthermia, restlessness, and sweating.
Based on human use, ginkgo may decrease side effects of antipsychotic drugs, although scientific information in this area is limited. There is a case report of "coma" in an elderly Alzheimer's patient taking trazodone and ginkgo, although it is not clear that this reaction was due to ginkgo. In theory, ginkgo may increase the actions of drugs used for erectile dysfunction such as sildenafil (Viagra®).
There may be a risk of seizure when taking ginkgo, particularly in people with a history of seizure disorder. Although most reports of seizures have been due to eating ginkgo seeds (not leaf extract which is found in most products), an animal study found that the anti-seizure properties of sodium valproate or carbamazepine were reduced by giving ginkgo. In theory, drugs such as donepezil (Aricept®) and tacrine (Cognex®) may have an additive effect when used at the same time as ginkgo, potentially increasing cholinergic effects (such as salivation and urination).
5-fluorouracil induced side effects and cyclosporine kidney toxicity may in theory be improved by ginkgo, although evidence is not conclusive in these areas. Colchicine has been found in commercial preparations of ginkgo, and may increase blood concentrations in patients using colchicine.
Ginkgo may alter the way the liver breaks down certain drugs.
Interactions with Herbs and Dietary Supplements
Use of ginkgo with herbs or supplements that may cause bleeding may increase the risk of bleeding, although some studies disagree. Several cases of bleeding have been reported with the use of garlic, and two cases with saw palmetto. Numerous other agents may theoretically increase the risk of bleeding, although this has not been proven in most cases.
Ginkgo has been found to decrease blood pressure in healthy volunteers, although some studies disagree. Theoretically, ginkgo may have additive effects when used with herbs or supplements that also decrease blood pressure. However, high blood pressure was reported in a patient taking a thiazide diuretic ("water pill") plus ginkgo. Although it remains unclear if ginkgo has clinically significant effects on blood pressure, caution may be warranted when ginkgo is used with other agents that affect blood pressure.
Based on human study, ginkgo may theoretically affect insulin and lower blood sugar levels. Caution is advised when using herbs or supplements that may also affect blood sugar. Blood glucose levels may require monitoring, and doses may need adjustment.
Effects on monoamine oxidase (inhibition) by ginkgo are reported in animals but not confirmed in humans. In theory, ginkgo may add to the side effects of herbs or supplements that also inhibit monoamine oxidase, such as 5-HTP (5-Hydroxytryptophan).
Based on laboratory research, ginkgo may add to the effects of herbs or supplements that affect levels of serotonin in the blood or brain, and could increase the risk of serotonin syndrome (a condition characterized by muscle stiffness, increased heart rate, hyperthermia, restlessness, and sweating).
Ginkgo may increase the actions of agents used for erectile dysfunction, including yohimbe.
Ginkgo may alter the way the liver breaks down herbs and supplements.