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What Are the Uses and Dangers of Kava?
By Michael Hirsch, M.D.
Featured in Harvard Mental Health Letter, November 2000

Kava (botanical name piper methysticum, or "intoxicating pepper") is a plant found on many South Pacific islands that has recently become popular in the United States as an herbal supplement. Its use predates any written histories of the South Pacific and was common long before the introduction of alcohol to that part of the world. Traditionally, the root is chewed or mashed, mixed with water or coconut milk, and strained. The resulting drink is used for ceremonial and social purposes, and also as a medicine in the treatment of boils, asthma, headache, urinary infections, and other physical conditions.

Kava is usually described as inducing pleasant, cheerful, and calm feelings. It has been compared to benzodiazepines such as diazepam (Valium) or alprazolam (Xanax) and advertised as a "natural alternative" to these anti-anxiety medications. The active components of the kava root, which are known as kava-lactones, interact with the same neuronal receptors (GABA receptors) that are affected by benzodiazepines. Other chemical components of the plant may have local anesthetic and muscle-relaxing properties.

Kava is commonly prescribed in Europe and has become increasingly popular in the United States as a mild anti-anxiety agent and sedative. However, there are few well-designed studies confirming its efficacy. In a recent review in the Journal of Clinical Psychopharmacology (Feb 2000), the authors conclude that kava extract seems to be superior to placebo as a treatment for anxiety, but they note that many of the studies reviewed involve small numbers of subjects and may be methodologically flawed.

Companies selling nutritional supplements claim that kava is a safe and natural alternative to standard anti-anxiety medications. But "natural" does not necessarily mean safe, or safer than standard treatments. Although studies so far suggest that kava has relatively few side effects, caution is necessary. Regular use may cause mild gastrointestinal disturbances. Prolonged use can give the skin a yellowish tint, and chronic consumption of large quantities may cause a dry, scaly rash called kava dermopathy. When kava is used along with another sedative drug, the combined effect can be harmful. There is one report of a man becoming semi-comatose after combining kava with his regular antianxiety medication. It has not been shown to be safe when combined with other drugs affecting the central nervous system, such as antidepressants. Pregnant or nursing mothers should not use kava, because its effects on a fetus or baby are unknown.

A common claim in the advertising for kava is that it is not addictive. That would be welcome, since most other substances with anti-anxiety or calming properties, such as benzodiazepines, barbiturates, and alcohol, pose a risk of abuse and addiction. Unfortunately, kava too can be abused. High doses cause symptoms of intoxication such as dizziness and muscle weakness. Among Australian aborigines, overuse of kava in the 1980s was associated with medical symptoms, and local groups recommended reducing consumption. These adverse effects were reflected in such newspaper descriptions as "Kava turns people into zombies" and "The kava killer." Yet information regarding abuse of kava is conspicuously absent from the advertising.

Kava is one of the best-selling herbal supplements in the nation, with a reported sales growth rate of 437% in 1998. The recommended dose is 100 mg of an extract of 70% kava lactones taken two or three times daily‹equivalent to 140-210 mg per day of the active substances. Because kava is marketed as an herbal supplement, vendors are not required to undergo the strict quality and safety evaluations mandated by the Food and Drug Administration (FDA) for substances considered to be medications. For the same reason, kava distributors cannot claim that their product is a treatment for a specific medical condition, such as an anxiety disorder; they can only use such phrases as "it helps you to relax." Because the FDA exercises no supervision, the potency and quality of commercially distributed kava cannot be guaranteed, and it may vary widely, as in the case of other herbal supplements such as St. John¹s Wort. There may also be a risk of adulteration with toxic substances.

To sum up, there is much anecdotal information suggesting that kava has mild calming properties and is fairly safe in low doses, but it cannot yet be recommended for the treatment of anxiety disorders. Adverse effects may result from prolonged use at high doses or in combination with other sedatives. Kava deserves further study, but until more reliable information is available, the standard treatments for anxiety disorders are recommended.

Used with permission from Harvard Health Publications.