Reason for posting: Health Canada advises that products containing kava should not be used.1 The drug is used in a variety of herbal and homeopathic preparations to induce relaxation, treat anxiety or induce sleep. Health Canada is unaware of any kava-related adverse events in Canada, but the US Food and Drug Administration recently issued a warning letter about 25 reports of serious liver toxicity in Germany and Switzerland, including cases of cirrhosis, hepatitis and liver failure. It also cited a case in the United States of a previously healthy young woman who required a liver transplant after using a kava-containing supplement.2
The drug: Kava lactones, also known as kava pyrones, are derived from the dried root and rhizome of Piper methysticum.3 Kava extract is used in traditional recreational drinks in many South Pacific countries.3,4 In Western societies, kava is used as an over-the-counter anxiolytic, muscle relaxant, mood enhancer, sedative or treatment for premenstrual syndrome.1,2 It is sold under different ingredient names (seebox).
Box 1.
A recent meta-analysis and a Cochrane review concluded that kava extract may be more effective than placebo as an anxiolytic in the short term,5,6 through a mechanism that is not well understood. Clinical trials of kava preparations have used doses of 70–240 mg of dried extract up to 3 times a day.4,7 However, many kava-containing products with drug identification numbers in the Health Canada drug product database contain 2000–3000 mg of extract per tablet.8
Several pharmacologic effects of kava have been observed, including platelet inhibition, difficulties with visual accommodation and photosensitivity, and possible dopaminergic antagonist activity. It was therefore recommended that kava not be used in conjunction with anticoagulants, antiplatelets or antipsychotics, or in patients with Parkinson's disease.3,10 Kava may also enhance the effects of other centrally acting agents such as benzodiazepines and alcohol.9
Long-term use of kava, especially in high doses (400 mg of kava pyrones daily),3 has been associated with the development of flaky, dry, yellow skin (kava dermopathy) through an unknown mechanism; the effect may be reversible upon cessation of the drug.4 Other possible adverse effects include ataxia, hair loss, hearing loss and anorexia.4
Health Canada is conducting a safety assessment to determine whether additional action (e.g., product recall) is required regarding kava-containing products. In the meantime, consumers are advised not to use these products.1
What to do: Physicians are asked to review cases of patients with liver toxicity and report any adverse events that may be related to the use of kava to Health Canada. Patients with signs or symptoms of possible liver disease should be asked about their use of herbal remedies. Also, physicians treating patients for stress, anxiety, insomnia or premenstrual syndrome should ask about self-treatment with herbal remedies and warn about risks related to kava. Physicians practising travel medicine may wish to warn patients (particularly those with liver disease, regular users of alcohol, those with Parkinson's disease or those using benzodiazepines or antipsychotic drugs) who will be visiting areas where kava is used recreationally of the potential exposures and risks.
Eric Wooltorton Editorial Fellow CMAJ
References
- 1.Health Canada is advising consumers not to use any products containing kava [advisory]. Ottawa: Health Canada; 2002 Jan 16. Available: www.hc-sc.gc.ca/english/protection/warnings/2002/2002_02e.htm (accessed 2002 Feb 19).
- 2.Lewis Taylor C. Dear health care professional colleague letter. Rockville (MD): US Food and Drug Administration; 2001 Dec 19. Available: www.fda.gov/medwatch/safety/2001/kava.htm (accessed 2002 Feb 19).
- 3.MacKinnon S. Kava. In: Chandler F, editor. Herbs: everyday reference for health professionals. Ottawa: Canadian Pharmacists Association, Canadian Medical Association; 2000. p. 145-6.
- 4.Ernst E. The risk-benefit profile of commonly used herbal therapies: ginkgo, St. John's wort, ginseng, echinacea, saw palmetto, and kava. Ann Intern Med 2002;136:42-53. [DOI] [PubMed]
- 5.Pittler MH, Ernst E. Efficacy of kava extract for treating anxiety: systematic review and meta-analysis. J Clin Psychopharmacol 2000;20:84-9. [DOI] [PubMed]
- 6.Pittler NA. Kava extract for treating anxiety [Cochrane review]. Cochrane Database Syst Rev 2001; 4:CD003383. [DOI] [PubMed]
- 7.Volz HP, Kieser M. Kava-kava extract WS 1490 versus placebo in anxiety disorders — a randomized placebo-controlled 25 week outpatient trial. Pharmacopsychiatry 1997;30:1-5. [DOI] [PubMed]
- 8.Drug product database. Ottawa: Health Canada. Available: www.hc-sc.gc.ca/hpb/drugs-dpd (accessed 2002 Feb 19).
- 9.Almeida JC, Grimsley EW. Coma from the health food store: interaction between kava and alprazolam. Ann Intern Med 1996;125(11):940-1. [DOI] [PubMed]
- 10.Meseguer E, Taboada R, Sanchez V, Mena MA, Campos V, Garcia De Yebenes J. Life-threatening parkinsonism induced by kava-kava. Mov Disord 2002;17:195-6. [DOI] [PubMed]