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NEW FDA Kava Warnings: How Safe is it?

Hyla Cass, MD
April 2, 2002

The Food and Drug Administration (FDA) is advising consumers of the potential risk of liver damage associated with the use of kava-containing dietary supplements. Indigenous to the islands in the South Pacific, kava (Piper methysticum) has become one of the top-selling herbs in the U.S., ranking ninth in retail sales in 2000. Kava's widespread popularity is based on its well-recognized ability to safely relieve stress, anxiety and tension sleeplessness, menopausal symptoms and other conditions.

Kava came under the scrutiny of the United States Food and Drug Administration (FDA) after a number of European reports that it might cause damage to the liver - including hepatitis, cirrhosis, and liver failure. German and Swiss health authorities have identified approximately 30 such cases, including four cases requiring transplantation, and one death. As a result, regulatory agencies in Germany, Switzerland, France, Canada, and the United Kingdom, have taken actions ranging from warning consumers about the potential risks of kava use, to removing kava-containing products from the marketplace. In the U.S., FDA has received several reports of kava-related liver damage, including a report of a previously healthy young woman who required a liver transplant. Although the incidence appears to be rare, FDA believes consumers should be informed of potential risks (see box below).

The Evidence So Far

Concerned by these reports, a coalition of U.S. trade associations from the dietary supplement and herbal industry responded by hiring a highly regarded professional toxicologist to evaluate the potential relationship between kava consumption and liver problems. After carefully analyzing the available data, his final report concluded that, based on the lack of specific clinical and historical information, "there is no clear evidence that the liver damage reported in the U.S. and Europe was caused by the consumption of kava." Additionally the report found that, even in instances of possible association between kava and liver damage, the cases appear to have been hypersensitivity or idiosyncratic-based responses. It also was shown that the vast majority 30 European cases, 21 in all, involved the concomitant use of hepatotoxic drugs and/or alcohol.

The report concluded that the medical community and the general public should be informed that kava should not be taken in conjunction with prescription drugs associated with liver damage, excessive alcohol consumption, and by those with pre-existing liver disease or with compromised liver function. At the same time, attention was drawn to two specific cases of consumption of very large quantities of kava, that, from a toxicological perspective, provide some evidence that kava itself is not a direct hepatotoxin, even in extremely high concentrations."

Research Results Show High Level of Safety

Prior research bears out his conclusions. Kava has a long tradition of safe use in the South Pacific as a ceremonial and medicinal drink, often at considerably higher doses than those used in Europe. In fact, the safety and toxicity of kava has been extensively studied in recent years, with very few reported liver toxic effects.

The longest running study conducted to date, with 101 people for 6 months taking 70 mg 3 times a day had negligible side effects, and in fact, the placebo group reported more side effects than those taking the kava. The researcher concluded that, in contrast to both benzodiazapines and antidepressants, kava possesses an excellent side-effect profile.

The safe and effective benefits of kava to relieve symptoms of anxiety were also supported in a meta-analysis, a systematic statistical review of seven human clinical trials published in 2000 in the Journal of Clinical Psychopharmacology, and again in a similar critical review in 2001. The reviews did not find significant adverse effects related to liver toxicity. In addition, a recent clinical study by Professor Jonathan Davidson and Dr. Kathryn Connor from Duke University, showed no liver abnormalities or other significant side effects.

In 1990 the German government's Commission E - a commissioned panel of experts in the fields of medicine and pharmacy - evaluated the scientific and medical literature. Their conclusion was that kava should be approved as a nonprescription medicine for "nervous anxiety, stress, and restlessness."

Kava Safer Than Conventional and OTC Drugs

The large number of published safety and toxicity studies clearly indicate that kava is far safer - and less hepatotoxic - than conventional pharmaceutical anti-anxiety and antidepressant prescription drugs.

For example, one is far likelier to suffer liver damage from the prescription anti-anxiety drug, Valium, which also carries the risk of other serious side effects, such as addiction and concomitant withdrawal symptoms that can include seizures.

Additionally, the leading single cause of liver failure in Western countries is overdose of the common pain medication, acetominophen (Tylenol). In fact, acetominophen overdose patients are placed in a special category as candidates for liver transplant because the speed of liver damage requires immediate treatment.

Despite the fact that prescription and over-the-counter drugs such Valium and acetominophen are taken by millions daily, there is very little public question as to their safety - and virtual no major adverse publicity.

Conclusion While a more thorough investigation is needed before drawing any final conclusions about kava's potential toxicity, this issue underscores the importance - and the vulnerability - of the liver. The liver is the body's principle chemical factory, responsible for a complex array of duties ranging from detoxification of ingested chemicals and filtering waste products to metabolizing nutrients for energy and storing excess energy for later conversion into fuel.

Ironically, while the topic here is the potential hepatotoxicity of an herb, the plant kingdom provides us with such life-saving liver-protective herbs as milk thistle. In fact, in my clinical practice I include milk thistle in the regimen of clients who have been exposed to liver-damaging drugs, both to protect the liver and to restore its vital function.

The current situation does point out that the liver is affected by many substances, including prescription and non- prescription drugs, as well as alcohol, which is a major cause of liver damage.

We must be aware that herbs are potent medicines, to be treated with the appropriate respect regarding potential interactions and toxicity, including to the liver. That being said, kava's margin of safety far surpasses that of its pharmaceutical equivalent. Nothing would be gained by previously satisfied consumers of kava, out of fear of these potential side effects, switching to a more toxic prescription medication, such as a benzodiazepine, in the mistaken belief that they were making a safer choice.

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