Herbs & Supplements

What interactions should I watch for?

Prescription Drugs

Taking some prescription drugs may increase the risk of liver damage. If kava, which may also result in liver damage, is taken at the same time as a potentially liver-damaging drug, the risk of potentially life threatening liver damage may increase even more. Drugs that may possibly damage the liver include:

• Anticonvulsants such as carbamazepine and valproic acid
• Antifungal drugs such as itraconazole, ketoconazole, and terbinafine
• Antiviral drugs such as nevirapine (Viramune) and ritonavir (Norvir)
• Arava
• azathioprine
• Cholesterol-lowering drugs (fibric acid derivatives) such as fenofibrate and gemfibrozil
• Cholesterol-lowering drugs (statins) such as Lipitor, lovastatin, pravastatin, and simvastatin
• Cognex
• isoniazid
• methotrexate
• Oral drugs for diabetes (glitazones) such as Actos and Avandia
• Precose
• rifampin
• tamoxifen

When kava is used with prescription drugs that promote sleepiness, the effects of the drug may be exaggerated, resulting in sedation or mental impairment. Prescription drugs that can cause sleepiness include:

• Anticonvulsants such as carbamazepine, phenytoin and valproic acid
• Barbiturates such as phenobarbital
• Benzodiazepines such as alprazolam and diazepam
• Drugs for insomnia such as Lunesta, Rozerem, Sonata, and zolpidem
• Tricyclic antidepressants such as amitriptyline, amoxapine, doxepin, and nortriptyline

In laboratory studies, kava has been shown to increase the time blood needs to clot. When it is taken with antiplatelet or anticoagulant drugs, the effect of the drug may be increased, possibly 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, kava may possibly interfere with the use of prescription drugs that are processed by the same enzymes. Some of these drugs are:

• Allergy drugs such as fexofenadine
• Antifungal drugs such as itraconazole and ketoconazole
• Cancer drugs such as etoposide, paclitaxel, vinblastine, and vincristine
• Drugs for high cholesterol such as lovastatin
• Oral contraceptives

Kava's potential to alter dopamine levels may interfere with the effectiveness of drugs such as carbidopa-levodopa (Sinemet), levodopa (Dopar), Mirapex, Requip, and selegiline (Eldepryl, Emsam, Zelapar), which mainly are used to treat Parkinson's disease.

Non-prescription Drugs

Rarely, some drugs that are sold without a prescription may cause damage to the liver. If these drugs are taken at the same time as kava, the risk of liver damage may increase. Oral non-prescription drugs that may be associated with liver damage include niacin (vitamin B-3) and antifungal drugs such as ketoconazole (Nizoral) and terbinafine (Lamisil).

The sleep-producing effects of over-the-counter products containing diphenhydramine or doxylamine may be enhanced by taking kava at the same time. Diphenhydramine and doxylamine are contained in many non-prescription sleeping pills as well as in some cough and cold products; therefore, caution should be used when taking these medications with kava because excessive drowsiness may result.

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

Herbal Products

If it is taken at the same time as other herbal products or dietary supplements that could affect liver function, kava might increase the chance of liver problems. Other herbs and supplements that may affect liver function include:

• Borage
• Comfrey
• DHEA
• Pennyroyal Oil
• Scullcap
• Uva Ursi
• Valerian

Kava may cause excessive sedation if it is taken with other potentially sedating herbs or supplements such as:

• Catnip
• Hops
• St. John's Wort
• Tryptophan
• Valerian

Theoretically, if kava is used with other herbs that affect blood clotting, 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)
• Ginkgo
• Horse Chestnut
• Panax Ginseng
• Papain

One case report suggests that kava's potential liver toxicity may be increased by St. John's wort. Therefore, the two herbals should not be used at the same time.

Foods

Drinking alcohol at the same time as using kava by mouth may result in increased drowsiness. Additionally, the risk of possible liver damage may increase.

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 kava interacts with drugs, other herbals, and foods and the severity of those interactions, please use our Drug Interactions Checker to check for possible interactions.