Herbs & Supplements

What interactions should I watch for?

Prescription Drugs

Ginkgo leaf is believed to increase the time blood needs to clot. When it is taken with antiplatelet or anticoagulant drugs, the effect of the drug possibly may be slightly increased, potentially resulting in uncontrolled bleeding.

• Antiplatelets include clopidogrel and Ticlid
• Anticoagulants include heparin and warfarin

Because it is broken down by certain enzymes in the liver, ginkgo leaf extract (GLE) may possibly interfere with the use of prescription drugs that are processed by the same enzymes. Although recent small studies of interactions with specific drugs have shown that ginkgo generally had no significant effects, other studies have shown a definite interference with major liver enzymes that break down drugs such as:

• Allergy drugs such as fexofenadine
• Antifungal drugs such as itraconazole and ketoconazole
• Cancer drugs such as Camptosar, etoposide, Gleevec, paclitaxel, vinblastine, or vincristine
• Drugs for high cholesterol such as lovastatin
• nicardipine (Cardene)and propranolol (Inderal), drugs for high blood pressure
• Oral contraceptives
• phenobarbital, which is used for insomnia and seizures

Either ginkgo leaf or ginkgo seed may make seizures more likely to occur for individuals who have had seizures in the past. Known as "lowering the seizure threshold", this effect may also decrease the effects of anticonvulsants--drugs to prevent seizures.
Anticonvulsants include:

• barbiturates such as phenobarbital
• benzodiazepines such as diazepam
• carbamazepine (Tegretol)
• Cerebyx
• divalproex
• Keppra
• lamotrigine
• oxcarbazepine.
• phenytoin (Dilantin)
• Topamax
• valproic acid
• zonisamide

Additionally, a chemical in ginkgo has blocked the effects of an immunosuppressant agent, cyclosporine for some individuals. Although they may be used to treat several conditions, immunosuppressants usually are given to prevent the rejection of transplanted organs. Interactions between ginkgo and other immunosuppressants have not been identified, but they are possible.

Ginkgo leaf may change the ways that the body makes and uses natural insulin. Therefore, it may also alter the effects of injected insulin. Individuals who inject insulin to control diabetes may experience changing blood sugar levels if ginkgo is also taken. Blood sugar may need to be monitored more closely and insulin doses may need more frequent adjustment.

Taking ginkgo leaf preparations may also interfere with oral drugs for diabetes, such as:

• acarbose
• Avandia
• glimepiride
• glipizide
• glyburide
• Glyset
• metformin
• Prandin

In several cases, taking ginkgo while a thiazide diuretic was also taken caused a rise in blood pressure. Usually taken to lower blood pressure, thiazide diuretics are drugs that promote the loss of water from the body. They include:

• chlorothiazide
• chlorthalidone
• hydrochlorothiazide
• metolazone
• polythiazide

In one small study, lower blood levels of omeprazole (Prilosec), a proton pump inhibitor, resulted when ginkgo was taken at the same time. Omeprazole is used to treat stomach and intestinal ulcers and esophageal conditions such as erosive esophagitis and gastroesophageal reflux disease (GERD). Possibly, ginkgo could interfere with omeprazole's effectiveness.

In a study of 14 healthy individuals, taking GLE for four weeks resulted in lower than expected blood levels of the drug, midazolam. Usually injected, midazolam is used as an anxiety-reliever and sedative during diagnostic procedures or before surgery. While the blood levels observed during the study did not change the effects of midazolam very much, individuals who take ginkgo leaf products may need to stop taking them before having a diagnostic or surgical procedure.

One case of coma has been reported in an elderly Alzheimer's disease patient who began taking GLE while also taking the antidepressant drug, trazodone (Desyrel). The patient recovered after emergency medical attention and discontinuation of both ginkgo and trazodone. Although the interaction has not been reported again, ginkgo and trazodone are not recommended for use together.

Non-prescription

Ginkgo leaf may decrease the ability of blood to clot after an injury. Aspirin can also delay clotting, so ginkgo leaf should not be taken orally at the same time as aspirin.

Some non-prescription products that are used to treat allergies or colds contain ingredients such as dexchlorpheniramine and pseudoephedrine, which may possibly make seizures more likely to recur. Although the risk is thought to be slight, taking any ginkgo product may also increase the possibility of seizures for individuals who have had seizures previously. Therefore, taking ginkgo at the same time as a non-prescription antihistamine or decongestant is not recommended.

Herbals

Theoretically, if ginkgo leaf is used with other herbs that may affect blood clotting, excessive bleeding may occur. Some of the most common herbal products that might inhibit blood clotting are:

• Danshen
• Devil's Claw
• Eleuthero
• Garlic
• Ginger (in high amounts)
• Horse Chestnut
• Panax Ginseng
• Papain
• Red Clover
• Saw Palmetto

Either ginkgo leaves or seeds may "lower the seizure threshold", which means they may make seizures more likely to recur in individuals who have had previous seizures. When ginkgo is taken with other herbal products that may also induce seizures, this risk increases. Some other herbals that may lower the seizure threshold include:

• Borage
• Evening Primrose
• Juniper
• Wormwood

Some interactions between herbal products and medications can be more severe than others. The best way for you to avoid harmful interactions is to tell your doctor and/or pharmacist what medications you are currently taking, including any over-the-counter products, vitamins, and herbals. For specific information on how ginkgo leaf products or ginkgo seeds interact with drugs, other herbals, and foods and the severity of those interactions, please use our Drug Interactions Checker to check for possible interactions.