Kava: a test case for Canada's new approach to natural health products
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Heather S. Boon and Albert H.C. Wong
From the Faculty of Pharmacy (Boon) and the Centre for Addiction and
Mental Health (Wong), University of Toronto, Toronto, Ont.
Correspondence to: Dr. Heather S. Boon, Faculty of Pharmacy, University of
Toronto, 19 Russell St., Toronto ON M5S 2S2; fax 416 978-1833;
[email protected]
In this issue, Edward Mills and colleagues 1 report the results of a study
in which simulated customers asked employees at 33 health food stores to
recommend a treatment for anxiety. Even though herbal kava had been the
subject of a Health Canada advisory, 2 employees in 22 (67%) of the 33
stores recommended kava. The simulated customers returned to the same
stores 2 months after Health Canada issued a stop-sale order for products
containing kava 3 and found that 17 (57%) of the 30 stores still in
business continued to sell it. These findings should be of concern to
health care professionals and consumers alike. The study by Mills and
colleagues 1 raises the questions of how Health Canada can enforce its
position on natural health products and what the impact on the health of
Canadians might be if stop-sale orders are ignored. Kava represents an
important test case with respect to Health Canada's approach to natural
health products, and thus it is important to place its story in the
context of the evolving regulations governing natural health products in
Canada.
Kava (Piper methysticum) is a herbal product commonly used to manage
symptoms associated with anxiety. Several reviews of the scientific
evidence from randomized, placebo-controlled, double-blind studies have
concluded that kava is an effective treatment for anxiety. 4, 5, 6, 7 The
recommended dose is 100 mg of kava extract (standardized to contain 70%
kavalactones) given 2 or 3 times per day, 8 but the receptor targets and
mechanism of action are not known. Until 2002, kava was generally
considered a safe herb with minimal adverse effects. However, 25 case
reports of serious toxic effects on the liver, including cirrhosis,
hepatitis and liver failure, associated with kava use in Germany and
Switzerland, 2 as well as the case of a woman requiring a liver transplant
in the United States, 9 raised concerns about the safety of kava. After
reviewing the international evidence and identifying 4 suspected cases of
liver toxicity associated with kava use in Canada, Health Canada issued a
stop-sale order for all products containing kava on Aug. 21, 2002. 3
Products containing kava were at that time available under Canadian food
or homeopathic drug regulations, which meant that consumers could purchase
them without consulting a health care provider and manufacturers did not
have to put warnings on the product labels. In its August 2002 stop-sale
order, Health Canada stated that there were "no acceptable food uses for
kava" and announced that kava products were to be regulated as
conventional drugs in the future. 3 It is important to note that Health
Canada did not "ban" kava, as was widely reported.
Several criticisms of the evidence for kava hepatotoxicity have been
raised. 10, 11 All of the data come from case reports, which are generally
considered a weak form of evidence. Some of the cases may have been
reported and counted more than once, and most of the patients were taking
other potentially hepatotoxic drugs, which makes it difficult to determine
causality. Data on concurrent alcohol consumption were often unavailable.
Liver toxicity generally occurred 2 to 3 months after kava intake (a
relatively long period between exposure and effect), and many case reports
did not indicate the duration of kava use. Finally, different types of
kava extract, as well as a synthetic kavain (a component of kava), are
sold, which further complicates interpretation of the case reports. Of 68
suspected cases reviewed by Ernst, 10 14 were assessed as probably being
caused by kava and 14 as possibly being caused by kava, including 3 severe
cases that resulted in the need for a liver transplant or death. However,
as noted by Stevinson and associates, 12 2 postmarketing surveillance
studies did not identify liver toxicity among a total of 7978 patients
taking 150 to 240 mg kava extract daily for approximately 6 weeks.
Health Canada's 2002 decision to reclassify kava as a conventional drug
appears prudent, given concerns about liver toxicity, even if this side
effect is rare. Kava is clearly not eaten as a food, and even low rates of
liver toxicity are not acceptable for any food. The decision means that
manufacturers selling kava in the future must empirically demonstrate the
safety of kava to gain approval under Canadian drug regulations. However,
another avenue will become available to manufacturers of kava products in
January 2004, when new natural health product regulations come into
effect, under the auspices of the Natural Health Products Directorate of
Health Canada. 13 Kava may be eligible for return to the Canadian market
under these regulations, provided the safety concerns can be mitigated
through appropriate use of warning labels or other measures.
The sale of kava in health food stores 2 months after a stop-sale order,
as reported by Mills and colleagues, 1 reflects the confusion surrounding
the regulation of herbs and its enforcement and suggests the need for
regulation not only of the products themselves, but also at the point of
sale. Informing consumers of the potential risks of nonprescription
pharmaceuticals through product labelling is a good idea, but the
differing opinions on the evidence of kava toxicity demonstrate that the
assessment of risks and benefits can be complex, and it might be a
considerable challenge to adequately equip the public to make informed
decisions about whether or not to use such products. We hope that the new
regulatory framework for natural health products will balance the need to
protect Canadians from unsafe compounds and preparations with the freedom
of individuals to make autonomous health care decisions.
See related article page 1158
Footnotes
Contributors: Both authors contributed substantially to the conception and
design of the article, and both were involved in drafting the article and
revising it critically for important intellectual content.
Competing interests: None declared.
References
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[Free Full Text]
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13. Natural Health Products Directorate. Welcome to the Natural Health
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Related articles in eCMAJ:
Sale of kava extract in some health food stores
Edward Mills, Rana Singh, Cory Ross, Edzard Ernst, and Joel G. Ray
eCMAJ 2003 169: 1158-1159. [Abstract]
[Full Text]
www.cmaj.ca/cgi/content/full/169/11/1158
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