A new study found high dosage, prolonged use and an inferior quality of kava contributed to the liver poisoning some people experienced in the late 90s.
Kava was banned in some countries, including Germany, after it caused liver disease in 83 people after 1998.
Professor Rolf Teschke from the Goethe University in the German city of Frankfurt has examined all German and Swiss people who suffered from liver problems after consuming kava.
Mr Teschke says there’s a similar pattern in all those cases.
“The patients have taken an overdose of kava and the duration of the therapy was also prolonged. [In] 1998 there was a real kava boom, it’s assumed that other kava cultivars,an inferior, toxic quality or variety, have been used.”
Rolf Teschke says farmers in the Pacific must find out what they have sold prior to 1998 and farm these safe varieties.
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Teschke has published a few articles on kava and toxic liver disease in German, including (note the word rare in the title):
Kava is a perennial shrub native to some islands of the South Pacific and has been cultivated for centuries to prepare a psychoactive beverage from its rhizoma by means of extraction. Subsequently, kava extracts are commonly used as herbal anxiolytic drugs also in many other countries all over the world including European ones and the USA. Toxicological and clinical studies have shown that kava extracts are virtually devoid of toxic effects with the exception of rare hepatotoxic side effects reported in few patients. When assessed primarily by the British regulatory authority MCA but also by us, a critical analysis of the suspected cases (n = 19) in Germany reveals that only in 1 single patient a very probable causal relationship could be established between kava treatment and the development of toxic liver disease due to a positive result of an unscheduled reexposure test, whereas in another patient there might be a possible association. Out of the remaining 17 cases 12 patients were not yet assessable due to insufficient data and in 5 other cases a causal relationship was unlikely or could be excluded. The German regulatory authority might therefore well be advised to provide now additional information for those 12 patients with so far unsatisfactory data, facilitating a more appropriate assessment of causality. Nevertheless, in the meantime physicians and patients should continue to keep an eye on possible hepatotoxic side effects in the course of kava treatment, to stop the treatment alredy at first suspicion and to start with a careful diagnostic work up ruling out all other causes.
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.
Toxic liver diseases caused by drugs, herbs and dietary supplements are often recognized late because their hepatotoxic potency is considered to be minimal or non-existent and specific laboratory parameters to definitively establish the diagnosis are lacking. As gold standard for the diagnosis, a positive (unintentional) re-exposure test is considered which is seldom available. A system for evaluation is therefore necessary which takes into account various parameters and defines the grades of causality. By means of a qualitative pre-test with a few questions a screening may be possible as to whether the causality is not probable or not evaluable. Subsequently, a quantitative assessment of the degree of the causality with a main test should be done; this corresponds to the slightly modified and well validated score of the CIOMS (Council for International Organizations of Medical Sciences). The evaluation is achieved using various criteria such as latency period, time between the end of the therapy and begin of the reaction, course of values for the enzyme activities of the liver after cessation of the therapy, risk factors such as age, alcohol consumption and comedication, exclusion of diseases of other organs including chronic liver disease, previous information about hepatotoxicity of the alleged substance and possible results of an unwanted re-exposure. The various answers to these questions are quantitatively assessed, the resulting scores added, and finally an assignment to one of the grades of causality is made. If, on the basis of the main test, there are still doubts about the correct diagnosis, a further test is required to consider the differential diagnosis of additional diseases and chronic liver diseases of other causes. This stepwise approach is essential since ad-hoc decisions regarding causality are not without problems, and other diseases as causes for increased liver values are easily overlooked and not treated adequately in time. By means of this procedure an improvement in the drug safety can be expected, which is fruitful for the patient and helpful to the physician in charge, the health institutions and the drug companies.
07-10-2008, 01:34
Prof. Rolf Teschke on Kava and Liver Damage
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