Kava, also known as Piper methysticum, is a tall shrub in the pepper family that grows in the South Pacific islands. It has been used there for thousands of years as a folk remedy and as a social and ceremonial beverage.
The part of the plant used medicinally is the root. Although the root was traditionally chewed or made into a beverage, kava is now available in capsule, tablet, beverage, tea, and liquid extract forms.
Why People Use Kava:
Because kava can cause sedation, and in high amounts, intoxication, kava drinks are consumed in some parts of the world in much the same way as alcohol.
How Kava Works:
The main active components in kava root are called kavalactones. Specific types of kavalactones include dihydrokavain, methysticin, kavain, dihydromethysticin, dihydrokawain, yangonin and desmethoxyyangonin.
Although it’s not clear exactly how kava works, kavalactones may affect the levels of neurotransmitters (chemicals that carry messages from nerve cells to other cells) in the blood. Kava has been found to affect the levels of specific neurotransmitters, including norepinephrine, gamma aminobutyric acid (GABA) and dopamine.
Scientific Evidence for Kava:
A number of well-designed studies have examined kava’s ability to relieve anxiety compared to anxiety medication or a placebo. The results have been promising.
In 2003, a review by the Cochrane Collaboration examined the existing research to see how kava fared compared to a placebo in treating anxiety. After analyzing the 11 studies (involving a total of 645 people) that met the criteria, the researchers concluded that kava "appears to be an effective symptomatic treatment option for anxiety." However, they added that it seemed to be a small effect.
Concerns About Kava and the Liver:
Although rare, case reports have linked kava use with liver toxicity, including hepatitis, cirrhosis, and liver failure.
As a result, the FDA has issued warnings about kava. Several countries have banned or restricted the sale of kava.
Clinical trials have not found liver toxicity. Adverse liver reactions appear to be linked to factors such as pre-existing liver disease, alcohol consumption, excessive doses, genetic variations in the cytochrome P450 enzymes, consumption of other drugs or herbs that, combined, may have a toxic effect, or the use of stem or leaf extracts or extracts made with acetone or ethanol.
Potential Side Effects of Kava:
Side effects include indigestion, mouth numbness, skin rash, headache, drowsiness and visual disturbances. Chronic or heavy use of kava has linked to pulmonary hypertension, skin scaling, loss of muscle control, kidney damage, and blood abnormalities.
Kava may lower blood pressure and it also may interfere with blood clotting, so it shouldn't be used by people with bleeding disorders.
People with Parkinson’s disease shouldn't use kava because it may worsen symptoms.
Kava should not be taken within two weeks of surgery. Pregnant and nursing women, children, and people with liver or kidney disease shouldn't use kava.
Possible Drug Interactions:
Kava shouldn't be taken by people who are taking Parkinson’s disease medications, antipsychotic drugs, or any medication that influences dopamine levels.
Kava shouldn't be combined with alcohol or medications for anxiety or insomnia, including benzodiazepines such as Valium (diazepam) or Ativan (lorazepam). It may have an additive effect if taken with drugs that cause drowsiness.
Kava may have an additive effect if combined with antidepressant drugs called monoamine oxidase inhibitors (MAOI).
Kava shouldn't be taken with any drug or herb that impairs liver function. Kava also may interfere with blood clotting, so people taking Coumadin (warfarin) or any drug that influences blood clotting should avoid it unless under a doctor's supervision.
Kava is a diuretic, so it may have an additive effect if combined with drugs or herbs that have diuretic properties.
Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy: Eclectic Medical, 1998.
Ernst E. "Safety concerns about kava." Lancet 359.9320 (2002): 1865.
Pittler MH, Ernst E. "Kava extract for treating anxiety." Cochrane Database Syst Rev. 2 (2002): CD003383.
The National Institute of Environmental Health Sciences. "Kava Kava". 2005 The National Institute of Environmental Health Sciences. 27 August 2007 <http://ntp.niehs.nih.gov/index.cfm?objectid=03DF99A0-E08D-7C9D-129744A0950D1847>.