Kava (Piper methysticum).

BACKGROUND: Kava is a plant indigenous to the Pacific Rim and the Hawaiian Islands whose root and rhizome are used to prepare a non-fermented beverage with relaxant effects that is used for social and recreational purposes. Kava roots are chewed or ground into a pulp and added to cold water, and the resulting brew—reported to mimic the effects of an alcoholic beverage—has been used as a ceremonial drink in the Pacific Islands for hundreds of years. While kava is considered a sacred plant in the South Pacific and is used in a variety of ceremonies, it is also used in traditional medicine to relieve anxiety, stress, fatigue, and insomnia, and to treat urinary tract infections and menopausal symptoms. It is believed that kava was introduced to the West by Captain James Cook in 1768. Over the past two decades, kava has gained popularity in Western countries, where it is promoted in supplemental form for anxiety, insomnia, and stress. It is available in health food stores and on the Internet in the form of tablets, capsules, liquid extracts, and tinctures. RESEARCH: Kavalactones, the compounds thought to be responsible for kava's activity, produce skeletal muscle relaxation, non-narcotic anesthestic effects, and local anesthetic effects. In vitro and in vivo studies suggest that these compounds induce mitochondrial dysfunction, oxidative stress, and apoptosis of human hepatocytes (Hep2G).[1,2] Animal studies suggest that kava's vasodepressor activity is mediated by a GABA receptor–sensitive pathway.[3] Kavapyrones also demonstrated additive effects with the serotonin 1A agonist, ipsapirone; these effects contribute to kava's sleep-inducing and anxiolytic properties.[4] Kava consumption has been associated with low cancer incidence,[5] but one of its constituents has been shown to stimulate the growth of melanoma cells.[6] Several clinical trials indicate that kava is superior to placebo for reducing anxiety.[7,8] However, reports of hepatotoxicity have led to restrictions on the use of kava-containing products.[9,10]