To the Editor: Gow and colleagues recently attributed fulminant hepatic failure in an Australian patient to an over-the-counter herbal product containing kava (Piper methysticum) that is extensively used in the community.1 We are not convinced that kava caused this patient’s liver failure. The hepatotoxicity could have been due to other unidentified contaminants of the herbal preparation or to chromium (from the mineral supplements also taken by the patient).

We tested a sample of the product Kava 1800 Plus (Eagle Pharmaceuticals, Batch No. 10711) by thin layer chromatography (TLC) and high pressure liquid chromatography (HPLC) methods, and assessed it against defined standards. Kavalactones were identified and quantified by normal-phase HPLC. Kava was positively identified, with a content of about 47 mg of kavalactones per tablet (the product label specifies 60 mg per tablet). However, flavonoids from Scutellaria lateriflora, analysed by reverse-phase HPLC, could not be found. Passiflora incarnata, analysed by TLC, was also not found, with none of the typical flavonoid bands being detectable.

The absence of two ingredients listed on the product label, P. incarnata and S. lateriflora, raises a new concern that there may be batch variations, as well as the possibility of unknown adulterants or contaminants being present. The possibilities of contaminants and batch variation were not excluded in the case report by Gow and colleagues.1 The Therapeutic Goods Administration established that Kava 1800 Plus did not contain common germander (Teucrium chaemaedrys), a known adulterant for S. lateriflora. However, Teucrium species are known to have hepatotoxic effects and there are about 100 species, any one of which could have been a contaminant.

Gow et al refer to 68 international case reports of suspected hepatotoxicity with the use of kava.1 An independent analysis of these 68 cases concluded that only two were probable kava-associated hepatotoxicities.2 An incidence calculation from these case reports indicates that hepatotoxicity from kava occurs in 0.008 cases per million daily doses,2 which represents an extremely low risk of adverse reactions associated with kava.

Recently, a study on the potential hepatotoxicity of kava found that the aqueous extract of kava does not affect results of liver function tests in rats. Extracts were administered in daily dosages of 200 or 500 mg of active kavalactones per kilogram of bodyweight for 2 or 4 weeks. Sera were assayed for four enzymes that are markers of liver toxicity, and liver homogenates were assayed for malondialdehyde formation, which indicates changes in lipid peroxidation. Kava did not elevate malondialdehyde or the enzymes alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase or lactate dehydrogenase. In fact, in certain instances, these enzymes were significantly reduced, suggesting a lack of toxic effect of kava on the liver.3 TLC analyses have shown that there is no qualitative difference between aqueous, acetone or ethanol extracts of kava.4

We propose, given that patients can consume other over-the-counter products such as chromium (shown to have hepatotoxicity at high concentrations),5 that all products consumed by patients must be evaluated before causality can be attributed to a particular herb. Reports of case records associated with hepatic failure due to kava require proper verification and documentation of all the findings.

In reply: Thomsen et al raise several points regarding our recent report of a death following ingestion of a preparation containing kava.1

The first is that the results of their analysis of the herbal preparation differ from those of the Therapeutic Goods Administration (TGA). The TGA found Passiflora incarnata in the tablets, whereas Thomsen and colleagues did not. The explanation for this lies in the fact that different batches of the product were analysed by the two laboratories. The analysis we reported relates to batch 13861, which was the source of the patient’s tablets. Thomsen and colleagues have analysed material from a different batch that may have contained different components.

Thomsen et al also raise the possibility that Teucrium, a known adulterant of Scutellaria, may have been present in the preparation. With respect to this issue, the TGA tested for both T. chamaedrys and T. canadensis and found none present. They also tested for the presence of the chemicals teucreoside and verbascoside, both of which are found in many Teucrium species. Neither was present. The raw materials used to make the tablets were also analysed, and no evidence of Teucrium substitution or contamination could be found.

The next point raised is whether the association between kava use and hepatotoxicity is causal, and they quote an analysis published in the journal Phytomedicine, in which the authors claimed that kava was the probable cause in only two of 68 reviewed cases. In marked contrast, the Journal of Hepatology, in July 2003, published an analysis of 36 cases of hepatitis associated with the use of kava.2 The review concluded that kava was the certain or probable cause of the hepatitis in 24 of the 36 cases. Worryingly, eight of these patients required liver transplantation.

Thomsen and colleagues then point to a lack of evidence of hepatotoxicity in studies in rats administered kavalactones.3 We believe it is inappropriate and misleading to suggest that a study of this kind could rule out the possibility that kava preparations cause life-threatening but uncommon idiosyncratic hepatotoxic reactions in humans.

Finally, Thomsen et al wonder whether the patient’s illness may have been due to chromium toxicity. However, the illness was not suggestive of chromium poisoning.4 There is no reason to believe that chromium was present at other than normal background levels.