Kava Side Effects and Warnings

Safety Issues

Until recently, kava had been considered a safe herb. Animal studies have shown that kava dosages of up to 4 times the normal amount cause no health problems, and 13 times the normal dosage causes only mild problems in rats. ¹ A study of 4,049 people who took a rather low dose of kava (70 mg of kavalactones daily) for 7 weeks found side effects in 1.5% of cases. These were mostly mild gastrointestinal complaints and allergic rashes. ² A 4-week study of 3,029 people given 240 mg of kavalactones daily showed a 2.3% incidence of basically the same side effects. ³ One review of the literature concluded that "the data support the safety of kava in treating anxiety at 280 mg kava lactones daily for 4 weeks." ⁴ However, a growing number of case reports have raised serious concerns about kava’s safety. These reports suggest that, occasionally, even normal doses of kava can cause severe liver injury. ^{5 6} Based on these reports, regulatory agencies have taken action in numerous countries banning or restricting sale of kava. However, case reports are notorious for failing to show cause and effect, and some well-regarded experts who have reviewed the literature feel that kava has not been shown to be unsafe. ⁷ In a report examining 26 alleged liver toxicity cases in kava users, consuming the herb at the recommended daily dose (less than 120 mg) and duration (less than 3 months) was clearly linked with only one case. ⁸ In all other cases, kava was either not implicated, was taken inappropriately, or was combined with another drug.

At present, if you wish to use this herb, we recommend that you seek physician supervision to monitor for liver inflammation. People with liver problems, who drink alcohol excessively, or who take medications that can harm the liver, are probably at increased risk of harm by kava.

There are other safety concerns as well. For example, kava should not be used by individuals who have had "acute dystonic reactions." These consist of spasms in the muscles of the neck and movements of the eyes, which are believed to be related to effects on dopamine. They are typically caused by antipsychotic drugs , which affect dopamine. Kava might trigger such reactions, too. ⁹ At ordinary doses, kava does not appear to produce mental cloudiness. ¹⁰ However, high doses cause inebriation ¹¹ and can lead to charges of driving under the influence of drugs.

One study suggests that kava does not amplify the effects of alcohol. ¹² However, there is a case report indicating that kava can increase the effects of certain sedative drugs. ¹³ For this reason, kava probably should not be combined with any drugs that depress mental function. Kava should also not be combined with antipsychotic drugs or drugs used for Parkinson's disease , due to the potential for increased problems with movement. ¹⁴ The German Commission E monograph warns against the use of kava during pregnancy and nursing. Safety in young children and individuals with kidney disease has not been established.

Interactions You Should Know About

If you are taking:

• Medications for insomnia or anxiety such as benzodiazepines : Do not take kava in addition to them.
• Antipsychotic drugs : Kava might increase the risk of a particular side effect consisting of sudden abnormal movements, called a dystonic reaction.
• Levodopa for Parkinson's disease: Kava might reduce its effectiveness.
• Medications that can irritate the liver: Avoid kava. Numerous medications have this potential. Ask your physician to see if this concern applies to you.