Current issues of ACP Journal Club are published in Annals of Internal Medicine


Therapeutics

Review: Kava extract reduces symptoms in adults with anxiety

PDF

ACP J Club. 2000 July-Aug;133:13. doi:10.7326/ACPJC-2000-133-1-013


Source Citation

Pittler MH, Ernst E. Efficacy of kava extract for treating anxiety: systematic review and meta-analysis. J Clin Psychopharmacol. 2000 Feb;20:84-9. [PubMed ID: 10653213]


Abstract

Question

In adults with anxiety, does kava extract reduce symptoms?

Data sources

Studies were identified by searching MEDLINE, EMBASE/Excerpta Medica, BIOSIS, AMED (British Library), CISCOM (Research Council for Complementary Medicine, London), and the Cochrane Library (to June 1998); scanning bibliographies of relevant articles and personal files; and contacting experts and the leading manufacturers of kava extract.

Study selection

Studies in any language were selected if they were randomized, double-blind, controlled trials (RCTs) that compared single preparations of kava extract with placebo. Names of authors, institutions, and journals and addresses were removed before selection.

Data extraction

2 reviewers independently assessed the quality of study methods by using the Jadad scale (maximum score of 5), and they extracted data on setting, study design, patient characteristics, kava extract regimen, Hamilton Rating Scale for Anxiety (HAM-A) scores, and adverse effects. Standardized, predefined criteria were used to extract data, and disagreements were resolved by discussion.

Main results

7 RCTs (377 patients) met the selection criteria. 6 RCTs had quality scores ≥ 3. The results of 3 RCTs (198 patients) that used a common outcome measure (HAM-A total score) were combined in a meta-analysis. The same kava extract dose was used in all 3 RCTs: kava extract WS1490, 100 mg 3 times daily for 4, 8, or 24 weeks. Kava extract led to a greater reduction in HAM-A total score from baseline than did placebo (weighted mean difference 9.69, 95% CI 3.54 to 15.83). The 4 studies that could not be combined in the meta-analysis reported a greater reduction in anxiety for kava extract than for placebo. 5 RCTs reported adverse effects in patients who received kava extract: stomach complaints, restlessness, drowsiness, tremor, headache, and tiredness.

Conclusion

In adults with anxiety, kava extract reduces symptoms.

Source of funding: Not stated.

For correspondence: Dr. M.H. Pittler, Department of Complementary Medicine, University of Exeter, 25 Victoria Park Road, Exeter EX2 4NT, England, UK. FAX 44-1392-424989.


Commentary

Anxiety symptoms and disorders are common in primary care and hospital services, but they often go unnoticed. They are disabling and frequently associated with depression and substance abuse. Conventional treatment is with antidepressants or benzodiazepines, but this therapy is usually only partially successful, with adverse effects described by many patients (1).

The meta-analysis by Pittler and Ernst suggests that kava extract may be a useful addition to the therapeutic options. The main result is derived from 3 relatively small trials, which is similar to the evidence base for antidepressants in anxiety (1). Most of the trials have been done in Germany; studies in other countries are both warranted and necessary. A mean reduction of 9 points on the HAM-A for the comparison of kava extract with placebo is likely to represent a clinically significant benefit, although the presentation of results does not allow direct comparison with other interventions for anxiety.

Some doctors may be skeptical that an herbal extract could be as effective as a synthetic drug. From that perspective, it is worth noting that some adverse effects were reported in 2% to 12% of the patients in the trials reviewed by Pittler and Ernst. Skepticism is fine if we are similarly wary for all new interventions and avoid double standards. Equally, we must guard against unbridled enthusiasm for a “natural” remedy. It is possible that some persons with anxiety will try kava extract before consulting their doctor. If they are started on other medications, the potential exists for substantial drug interaction, as has been seen with St. John’s wort in the treatment of depression.

Physicians have a new treatment option for anxiety, but they will need to avoid polytherapy and carefully monitor for possible drug interactions.

Stephen M. Lawrie, MD
Royal Edinburgh Hospital
Edinburgh, Scotland, UK


Reference

1. Gale CK, Oakley-Browne M. Anxiety disorder. Clinical Evidence. 1999;2:347-53.