Kava or kava-kava (Piper methysticum) (Piper: Latin for 'pepper', methysticum: (Latinized) Greek for 'intoxicating') is a crop of the western Pacific.
The name kava(-kava) is from Tongan and Marquesan; other names for kava include ʻawa (Hawaiʻi), 'ava (Samoa), yaqona (Fiji), and sakau (Pohnpei).
The roots of the plant are used to produce a drink with sedative and anesthetic properties. Kava is consumed throughout the Pacific Ocean cultures of Polynesia including Hawaii, Vanuatu, Melanesia and some parts of Micronesia. Kava is sedating and is primarily consumed to relax without disrupting mental clarity. Its active ingredients are called kavalactones. A Cochrane Collaboration systematic review of its evidence concluded that it was likely to be more effective than placebo at treating short-term social anxiety. Safety concerns have been raised over liver toxicity largely due to the use of stems and leaves by supplement makers, as opposed to solely the root of the plant as dictated by traditional uses. However, based on a retrospective study of retained P. methysticum drug materials in Germany, the alkaloid pipermethystine, occurring to about 0.2% in the leaves, is an unlikely cause for the observed hepatotoxicity. Whether kava hepatotoxicity may be due to contamination with aflatoxins or other mould hepatotoxins, requires further studies. Heavy use of kava with comorbid alcohol consumption or an existing liver condition appears to lead to malnutrition, weight loss, liver damage (causing elevated serum γ -glutamyl transferase and high-density lipoprotein cholesterol levels), renal dysfunction, rashes, pulmonary hypertension, macrocytosis of red cells, lymphocytopenia, and decreasing platelet volumes.