[Kava, kavapyrones and toxic liver injury].

Kava extracts are obtained from the rhizoma of the kava shrub (Piper methysticum) and contain various pyrones which are used as herbal anxiolytic remedies for generalized anxiety syndromes of low and intermediate grades. The commonly recommended daily dose of 60-120 mg kavapyrones and the duration of the therapy of up to 3 months should not be increased without consultation of a physician and were not followed by most patients, since herbal drugs are considered by the population not only as effective but also as safe. Whereas kava extracts are well tolerated by most patients and rare side effects are rapidly reversible upon drug discontinuation, there are suspected hepatotoxic reactions reported during the last years in temporal and not necessarily causal association with a therapy with kava extracts. Almost 80 % of the patients took kavapyrones in overdose (maximally 480 mg/d) and/or for a prolonged time of more than 3 months up to 2 years. Additional risks factors include co-medication with up to 5 other chemically defined or herbal drugs with in part potentially hepatotoxic properties as well as a genetic deficiency of the hepatic microsomal cytochrome P450 2D6. Severe clinical courses with liver transplantation and possible fatal outcome occurred in 7 patients with overdose and/or long duration of the therapy with kavapyrones. Preventive measures should therefore include a dose of 120, maximally 210 mg kavapyrones per day for 1 month, maximally 2 months, as well as a prescription by a physician. Laboratory test (ALT and gamma-GT) should be done before and during the therapy, and co-medication and alcohol consumption should be avoided. With these measures the hepatotoxic risks under the treatment with kavapyrones might be minimized which are also available via internet and from abroad with possible severe consequences when taken without medical supervision.