Are there any side effects or interactions?
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.14
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.15 Since that time, four case reports of kava-related
liver toxicity have appeared in medical journals.16 17 18
19 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.20 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.21 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.
It is also unclear whether kava is safe when taken in “normal” amounts. A
recent survey of 400 German medical practices revealed that 78% of the kava prescriptions that
were written significantly exceeded the recommended amount.22 However, some of the
24 patients reported to German authorities were not exceeding the manufacturer’s
recommended level of intake when they developed liver disease. In addition, in two of the four
published case reports, the amount of kava used was equal to or only slightly higher than the
manufacturer’s recommendation.23 Therefore, one cannot assume that the
recommended level of intake of kava is safe for all individuals.
Health authorities worldwide are considering or implementing a ban on kava. Until
additional information clarifies the extent of the risk involved, it is strongly recommended
that all individuals consult their physician before taking kava. In addition, based on the
available information, it seems that people with liver disease and those taking medications
that have the potential to damage the liver should not take 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.24 If this occurs, people should discontinue kava use. In rare cases, an
allergic skin reaction, such as a rash, may occur.25 Enlargement of the pupils has
also been reported after long-term use of kava.26 In the amounts discussed above,
kava does not appear to be addictive.
Kava is not recommended for use by pregnant
or breast-feeding women. It 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.27 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.28 One study found it was
safe to drive after taking kava at the amounts listed above.29 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.30
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.31 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.
Are there any drug
interactions?
Certain medicines may interact with kava. Refer to drug interactions for a list of those medicines.
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20. Information provided by the German Federal Institute for Drugs and
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Aust 1988;148:548–55.
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27. Foo H, Lemon J. Acute effects of kava, alone or in combination with
alcohol, on subjective measures of impairment and intoxication and on cognitive performance.
Drug Alcohol Rev 1997;16:147–55.
28. Almeida JC, Grimsley EW. Coma from the health food store: Interaction
between kava and alprazolam. Arch Intern Med 1996;125:940–1.
29. Herberg KW. Driving ability after intake of kava special extract WS
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