Kava's therapeutic uses

• PRINCIPAL PROPOSED USE: Anxiety

• OTHER PROPOSED USES: Alcohol withdrawal, headaches, insomnia, tension headaches

DEFINITION: Natural plant product used to treat specific health conditions.

Overview

Kava (Piper methysticum) is a member of the pepper family that has long been cultivated by Pacific Islanders for use as a social and ceremonial drink. The first description of kava came to the West from Captain James Cook on his celebrated voyages through the South Seas. Cook reported that on occasions when village elders and chieftains gathered for significant meetings, they would hold an elaborate kava ceremony. Typically, each participant would drink two or three bowls of chewed kava mixed with coconut milk. Kava was also drunk in less formal social settings as a mild intoxicant.

When they learned about kava’s effects, European scientists set to work trying to isolate its active ingredients. However, it was not until 1966 that substances named kavalactones were isolated and found to be effective sedatives. One of the most active of these is dihydrokavain, which has been found to produce a sedative, painkilling, and anticonvulsant effect. Other named kavalactones include kavain, methysticin, and dihydromethysticin.

High doses of kava extracts are thought to cause muscle relaxation and even paralysis (without loss of consciousness) at very high doses. Kava also has local anesthetic properties, producing peculiar numbing sensations when held in the mouth.

The kava method of action is not fully understood. Conventional tranquilizers in the Valium family interact with special binding sites in the brain called GABA receptors. Early studies of kava suggested that the herb does not affect these receptors. However, other studies found an interaction. Early researchers may have missed the connection because kava appears to affect somewhat unusual parts of the brain. An accumulation of case reports suggests that kava products may rarely cause severe liver injury, and this has led to a banning of kava by many countries.

Therapeutic Dosages

A typical dosage of kava, when used for the treatment of anxiety, is 300 to 400 milligrams (mg) daily of a product standardized to contain 70 percent kavalactones. A lower dose of 150 mg daily has also been tested but may be less effective. The typical dosage for insomnia is 210 mg of kavalactones one hour before bedtime.

Some supplements are available as tea, but tablets are also available. Kava has been documented to be safe for use for up to two years.

Therapeutic Uses

In 1990, Germany’s Commission E authorized the use of kava for relieving “states of nervous anxiety, tension, and agitation,” based on evidence from several double-blind studies. However, case reports of liver damage later led Germany and other countries to ban the sale of kava.

Like other anxiety-reducing drugs, kava could be useful for insomnia, but most of the supporting evidence for this use remains highly preliminary. One small, double-blind study found that daily use of kava reduced sleep disturbances linked to anxiety. However, a larger study failed to find benefits in people with both insomnia and anxiety.

One animal study suggests that kava may also have value as an aid to alcohol withdrawal. (However, individuals who abuse alcohol are probably at increased risk of harm from kava.) Kava has been additionally proposed as a treatment for tension headaches, but it has not been evaluated for this purpose.

Scientific Evidence

Anxiety. Many placebo-controlled studies of kava involving more than seven hundred people have found kava helpful for anxiety symptoms, but further research is necessary.

One of the best of these was a six-month, double-blind study that tested kava’s effectiveness in one hundred people with various forms of anxiety. During the trial, they were evaluated using the Hamilton Anxiety Scale (HAM-A). The HAM-A asks questions and assigns a total score based on such symptoms as restlessness, nervousness, heart palpitations, stomach discomfort, dizziness, and chest pain. Lower scores indicate reduced anxiety. Participants given kava showed significantly improved scores beginning at eight weeks and continuing throughout the treatment.

This study is notable for the long delay before kava was effective. Previous studies had shown a good response in one week. The reason for this discrepancy is unclear.

Several double-blind, placebo-controlled studies have specifically tested kava for the treatment of the anxiety that often occurs during menopause. In one study, forty women were given either kava plus standard hormone therapy or hormone therapy alone for six months. The results showed that women given kava experienced greater improvement in symptoms than those given hormone therapy alone.

However, not all studies have been positive. One double-blind, placebo-controlled study failed to find kava effective for people with generalized anxiety disorder. Another study failed to find kava more effective than a placebo for people with anxiety and insomnia.

Besides these placebo-controlled studies, one six-month, double-blind study compared kava against two standard anxiety drugs (oxazepam and bromazepam) in 174 people with anxiety symptoms. Improvement in HAM-A scores was about the same in all groups. Another study found kava and the drugs buspirone and opipramol equally effective.

A five-week, double-blind, placebo-controlled trial studied forty people who had been taking standard antianxiety drugs (benzodiazepines) for an average duration of twenty months. Participants were gradually tapered off their medications and switched to kava or placebo. Individuals taking kava showed some improvement in anxiety symptoms. This would appear to indicate that kava can successfully be substituted for benzodiazepine drugs. However, participants who were switched from benzodiazepines to placebo showed little to no increase in anxiety, suggesting that perhaps they did not need medication after all. Thus, the results of this study are hard to interpret.

This trial involved close medical supervision and a very gradual tapering of benzodiazepine dosages. Individuals should not discontinue antianxiety medications without supervision because withdrawal symptoms can be life-threatening.

One study purported to find evidence that kava helps reduce reactions to stressful situations. However, the results mean little because the study lacked a placebo group. Most studies indicate that kava's use as an anti-anxiety agent requires at least five weeks to begin to see its impact. However, long-term use is unsafe, and kava has not been studied for use in humans for more than two years. Some research indicates kava should not be taken for longer than four weeks.

Safety Issues

Kava was long considered a safe herb. Animal studies have shown that kava dosages of up to four times the normal amount cause no health problems, and thirteen times the normal dosage causes only mild problems in rats. A study of 4,049 people who took a relatively low dose of kava (70 mg of kavalactones daily) for seven weeks found side effects in 1.5 percent of cases, primarily mild gastrointestinal complaints and allergic rashes. A four-week study of 3,029 people who received 240 mg of kavalactones daily showed a 2.3 percent incidence of basically the same side effects. One review of the literature concluded that the data support kava’s safety in treating anxiety with 280 mg of kava lactones daily for four weeks.

However, many modern case reports have raised serious concerns about kava’s safety, even in normal doses, which may cause severe liver injury. At ordinary doses, kava does not appear to produce mental cloudiness, but high doses cause inebriation. Individuals who use the supplement should not drive after taking kava. One study suggests that kava does not amplify the effects of alcohol, but most research indicates the combination may cause irreparable liver damage.

Some well-regarded experts who have reviewed the literature criticizing kava's safety feel that it is not unsafe. In a report examining twenty-six alleged liver toxicity cases in kava users, consuming the herb at the recommended daily dose of less than 120 mg and over a duration of less than three months was clearly linked with only one case. In all other cases, kava either was not implicated, was taken inappropriately, or was combined with another drug. Despite some advocation for the herb’s use, more than twenty-five documented deaths have resulted from using kava in the United States and Europe.

Individuals who wish to use this herb should 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 at an increased risk of harm by kava. 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, but kava might also trigger such reactions. Individuals taking antipsychotics and individuals with Parkinson’s disease should not use kava to avoid increased involuntary muscle spasms. Additionally, one case report indicates that kava can increase the effects of certain sedative drugs. For this reason, kava should not be combined with any drugs that depress mental function.

Based on these concerns, regulatory agencies have taken action in numerous countries banning or restricting the sale of kava. The German Commission E monograph warns against using kava during pregnancy and nursing. Safety in young children and individuals with kidney disease has not been established. Some countries have banned kava imports, but they remain available and legal in the United States.

Important Interactions

Individuals who are taking medications for insomnia or anxiety, such as benzodiazepines, should not take kava in addition to them. For people who are using antipsychotic drugs, kava might increase the risk of a particular side effect consisting of sudden abnormal movements, called a dystonic reaction. Kava also might reduce the effectiveness of levodopa, which is taken for Parkinson’s disease. Additionally, individuals taking medications that can irritate the liver should avoid kava. Numerous medications have this potential, and individuals should consult a physician to determine whether this concern applies to them.

Bibliography

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Geier, F. P., and T. Konstantinowicz. “Kava Treatment in Patients with Anxiety.” Phytotherapy Research, vol. 18, 2004, pp. 297-300.

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