|Scientific Names: piper methysticum
Common Names: ava, awa, kava-kava, kawa, kew, sakau, tonga, yati, yangona
Kava is a shrub originally from the New Hebrides islands in the South Sea. Kava is one of the best selling herbal supplements in the US, with a reported sales growth of 437% in 1998.2 However, sales of the herb have been restricted in a number of countries including Australia, Canada, France, Germany, and Switzerland based on documented hepatic failure in combination with taking this supplement.
•Local anesthetic effect by first stimulating, then depressing peripheral nerve endings.
• A systematic review and meta-analysis of randomized, placebo-controlled, double-blind trials was carried out in 2000 to assess the efficacy of kava extract for treating anxiety. Using scores on the Hamilton Rating Scale for Anxiety (HAM-A) as the common outcome measure in these studies, the authors noted a significant decrease in anxiety for the experimental groups taking 60 to 240 mg of a standardized kavapyrone extract daily versus the placebo group.6 The authors of this study indicate that the sample sizes in most of the trials that they looked at were small, and lacked proper power calculation. Despite this, the evidence from the meta-analysis would seem to corroborate some of the anecdotal effectiveness of kava on anxiety.
•In animal studies, kava extract appears to enhance binding of muscimol, a GABA-A receptor agonist, in a concentration dependent manner.3 On studies of human platelets kava extract and pure synthetic kavalactones reversibly inhibit MAO-B, perhaps pointing to an important mechanism for the psychotropic effects of kava.9
•Human EEG studies show prolonged phases of deep sleep (III and IV) as well as REM phase sleep during a treatment period with single doses of either 150 or 300 mg of kava extract. This would appear to be more favorable an effect than treatment with benzodiazepines and barbiturates which depress both REM and deep sleep.7
•A study in 2002 demonstrated that 5 novel compounds extracted from kava roots all demonstrated good COX-1 and moderate COX-2 in vitro enzyme inhibitory activities at 100µg/mL. The authors suggest that this may provide some scientific support for the anecdotal claims of Pacific Islanders that kava helps to control inflammatory pain.
Adverse Effects, Contraindications, Drug Interactions:
•Authors of a 'mini-review' of kava efficacy and safety state that from an observation of 4,049 patients consuming 105 mg of kavalactones daily for seven weeks, there were only 61 cases (1.5%) of reported undesired effects, including mild and reversible gastrointestinal disturbances and allergic skin reactions.
•Paralysis of respiratory drive in large doses.
•On March 25, 2002, the FDA issued a consumer advisory dealing with the potential hepatic toxicity associated with kava use. In this advisory, 2 cases of liver failure in the US were investigated, including that of a 45 year old woman with sub-fulminant hepatic necrosis 8 weeks after beginning a regimen of a kava-containing supplement, and a 14 year old girl with active fulminant hepatitis and extensive centrilobular necrosis after an estimated 44 days of taking a unknown dose of a kava supplement. The advisory alerts consumers and health-care providers to this potential risk for hepatic toxicity, and calls for additional caution in persons with a pre-existing liver condition.
•A case report from 2002 details the development of severe and persistent parkinsonism in a 45 year old female with familial essential tremor, after only 10 days of taking a 65 mg/day dose of kava for anxiety.
•Prolonged use can give the skin a yellowish tint, and the chronic consumption of large quantities may cause a dry, scaly rash (kava dermopathy).
•Combination with other central nervous system depressants (alcohol, benzodiazepines, barbiturates) may produce dangerous levels of sedation.
1. Bilia AR, Gallori S, Vincieri FF. Kava-kava and anxiety: growing knowledge about the efficacy and safety. Life Sciences. 2002;70:2581-2597.
2. Harvard Men's Health Letter. Harvard Health Publications. November 2002.
3. Jussofie A, Schmiz A, Hiemke C. Kavapyrone enriched extract from piper methysticum as modulator of the GABA binding site in different regions of rat brain. Psychopharmacology. 1994;116:469-474.
4. Meseguer E, Taboada R, Sánchez V, et al. Life-threatening parkinsonism induced by kava-kava. Movement Disorders. 2002;17:195-196.
5. Morbidity and Mortality Weekly Report. Hepatic toxicity possibly associated with kava-containing products - Unites States, Germany, and Switzerland, 1999-2002. JAMA. 2003;289:36-37.
6. Pittler MH, Ernst E. Efficacy of Kava Extract for Treating Anxiety: Systematic Review and Meta-Analysis. J Clin Psychopharmacol. 2000;20:84-89. 7. Schultz H, Jobert M, Hübner WD. The quantitative EEG as a screening instrument to identify sedative effects of single doses of plant extracts in comparison with diazepam. Phytomedicine. 1998;5:449-458.
8. Skidmore-Roth L. Mosby's handbook of herbs and natural supplements. St. Louis: Elsevier Science Imprints. 2001.
9. Uebelhack R, Franke L, Schewe HJ. Inhibition of platelet MAO-B by kavapyrone-enriched extract from kava-kava. Pharmacopsychiatry. 1998;31:187-192.
10. Wu D, Nair MG, DeWitt DL. Novel compounds from piper methysticum forst (kava kava) roots and their effect on cyclooxygenase enzyme. J Agric Food Chem. 2002;50:701-705.