Kava

Kava is a member of the pepper family and is native to many Pacific Ocean islands. The rhizome (underground stem) is used in modern herbal preparations.

Caution: Kava should be taken only with medical supervision. Its safe use is not established.

A nonalcoholic drink made from the root of kava played an important role in social ceremonies in some Pacific islands, including welcoming visiting royalty and at meetings of village elders. Kava was valued both for its mellowing effects and to encourage socializing. It was also noted for initiating a state of contentment, a greater sense of well-being, and enhanced mental acuity, memory, and sensory perception. Kava has also been used traditionally by healers in the Pacific islands to treat pain.

The kava-lactones, sometimes referred to as kava-pyrones, are the most important active constituents in kava extracts. High-quality kava rhizome contains 5.5–8.3% kava-lactones.¹ Medicinal extracts used in Europe contain 30–70% kava-lactones. Kava-lactones are thought to have anti-anxiety, mild analgesic (pain-relieving), muscle-relaxing, and anticonvulsant effects.^{2, 3} Some researchers speculate that kava may directly influence the limbic system, the ancient part of the brain associated with emotions and other brain activities.⁴ Kava is a unique anti-anxiety alternative because it does not seem to impair reaction time or alertness when used in the amounts recommended below.⁵

Kava has been extensively studied as a treatment for anxiety.⁶ The amount often used in clinical trials is 100 mg of an extract (standardized to 70% kava-lactones) three times per day. Double-blind trials, including one that lasted six months, have shown that kava effectively reduces symptoms of anxiety in people with mild to moderate anxiety.^{7, 8} One trial found that kava also reduced symptoms of anxiety in menopausal women,⁹ and in another study kava enhanced the anti-anxiety effect of hormone replacement therapy.¹⁰ One trial found kava to be just as effective as benzodiazepines (a common class of drugs prescribed for anxiety) in treating mild anxiety over the course of six weeks.¹¹

For treatment of mild to moderate anxiety, kava extracts supplying 120–240 mg of kava-lactones per day in two or three divided doses are commonly recommended.¹² Alternatively (although it has not been researched), 1–3 ml of fresh liquid kava tincture can be taken three times per day. Kava should not be taken for more than three months without the advice of a physician, according to the German Commission E monograph.¹³

Caution: Aside from the reported interactions, kava inhibits a number of the cytochrome P450 enzymes that play a role in the breakdown of many medications.¹⁴ Therefore, kava has the potential to interact with a wide range of medications, even if such interactions have not yet been reported. Individuals taking any medication who wish to use kava should check with their physician or pharmacist to determine whether inhibiting cytochrome P450 could cause an adverse drug interaction.

Kava should not be taken together with other substances that also act on the central nervous system, such as alcohol, barbiturates, antidepressants, and antipsychotic drugs. One study found that large amounts of a traditional kava preparation did worsen cognitive impairment caused by alcohol consumption.¹⁵ However, at the amounts recommended above, kava does not appear to impair cognitive performance. Kava has also been reported to cause excessive sedation and grogginess when combined with benzodiazepines.¹⁶ One study found it was safe to drive after taking kava at the amounts listed above.¹⁷ However, the German Commission E monograph states that kava, when taken at the recommended levels, may adversely affect a person's ability to safely drive or operate heavy machinery.¹⁸

In November 2001, German authorities announced that 24 cases of liver disease (including hepatitis, liver failure, and cirrhosis) associated with the use of kava had been reported in Germany; of these, one person died and three required a liver transplant.¹⁹

Prior to this report, it had been widely believed that kava did not cause any serious side effects. The 1998 edition of the German Commission E Monographs, considered to be an authoritative source on herbal medicines, does not mention liver disease in its discussion of kava's side effects.²⁰ Since that time, four case reports of kava-related liver toxicity have appeared in medical journals.^{21, 22, 23, 24} In two of these cases, severe liver failure resulted in the need for a liver transplant. Most, though not all, of the individuals who developed liver damage while taking kava were also taking at least one other medication that has been associated with liver injury.²⁵ That raises the possibility that these other drugs, rather than kava, may have been responsible for the problem in some cases. It is also conceivable that kava interacts with some of these drugs, thereby increasing their toxicity. However, some of the cases of kava-related liver disease cannot be explained by the concomitant use of other drugs.

The possibility that kava can cause liver damage is supported by a survey of an Aboriginal community in Australia. Although occasional users of kava in this community generally had normal liver function, laboratory evidence of liver injury was quite common among heavy users of the herb.²⁶ Furthermore, the risk of liver damage was directly related to the amount of kava consumed. It is not clear how relevant these findings are to other communities, since the overall health of the Aborigines who were studied was relatively poor.

More recent evidence suggests that liver injury resulting from kava extracts was due to the use of inappropriate kava varieties and plant parts. Evidence indicates that the peeled kava rhizome should be used, but in some instances the plant's aerial parts (which may contain a toxic compound) have been used. It is now believed that kava products are safe if they are water-based extracts derived from peeled rhizomes and roots of a noble cultivar such as Borogu, of at least five years of age, and taken in amounts not exceeding 250 mg of kavalactones per day.²⁷ Despite this new information, it is strongly recommended that all individuals consult their physician before taking kava.

In recommended amounts, the most common side effect from kava use is mild gastrointestinal disturbances in some people. Kava may temporarily turn the skin yellow, according to some case studies.²⁸ If this occurs, people should discontinue kava use. In rare cases, an allergic skin reaction, such as a rash, may occur.²⁹ Enlargement of the pupils has also been reported after long-term use of kava.³⁰ In the amounts discussed above, kava does not appear to be addictive.

Kava is not recommended for use by pregnant or breast-feeding women.