Scientific Name: Kava-Kava
Other Names: Awa, Kava, Kawa, Kew, Piper methysticum, Tonga, Yagona

Who is this for?

Uses

Note: In March 2002, the U.S. Food and Drug Administration (FDA) issued a warning that taking kava has been associated with cases of liver damage. The FDA recommends that individuals — especially those with liver diseases or those taking medications that might impair liver function — discuss the use of kava with a healthcare professional before they begin taking it.

Britain, Canada, and the countries of the European Union have prohibited the sale of all kava products due to their potentially severe side effects, as well as to the likelihood that kava interacts with numerous other substances. Since the ban went into effect, however, some countries have resumed limited sales of kava. Other countries, including the United States, are considering whether or not to take it off the market. Currently, the World Health Organization (WHO) is re-considering the safety of kava.

In Western cultures, kava most often has been used to reduce anxiety and treat insomnia, although results of some recent clinical trials have not shown that is more effective than placebo (inactive sugar pills) for either condition. It does contain chemicals known as kava lactones (also called kava pyrones) that appear to have several calming effects on the central nervous system (CNS). However, unlike some other antianxiety and sedative drugs, the chemicals in kava do not seem to interfere with blood pressure, breathing, heart rate, or thinking. Kava lactones may affect the amounts certain neurotransmitters in the blood. Neurotransmitters are chemicals that carry messages from nerve cells to other cells. Taking kava may keep the body from re-absorbing one neurotransmitter known as norepinephrine. The resulting increased blood levels of norepinephrine may be associated with lessened anxiety and relaxed mood. The lactones in kava may also cause the body to produce more attachment sites for another neurotransmitter, gamma aminobutyric acid (GABA). More GABA sites may mean more GABA activity, which promotes sedation. Other ways that kava might work are to block the action of an enzyme known as monoamine oxidase-B (MAO-B) and to affect levels of a third neurotransmitter, dopamine, but in unpredictable ways. Although both MAO-B and dopamine play roles in emotional balance, the results of kava’s effects on them are unclear.

Its calming effects have made kava a subject of laboratory studies for various other types of CNS conditions including attention deficit activity disorder (ADHD), depression, epilepsy, and psychoses. However, no major human studies are underway, and not enough is known about kava’s activity in any of these CNS disorders to recommend its use. Presently, the FDA advises consumers that the risk of severe side effects, although very small, outweighs the possible benefits of taking kava for any reason.

When should I be careful taking it?

Individuals who have or who have ever had liver conditions should avoid taking kava because it may cause liver damage.

Individuals with Parkinson's disease usually have low levels of the neurotransmitter dopamine. Kava may increase or decrease amounts of dopamine in the body, possibly worsening Parkinson's symptoms.

Pregnant and breast-feeding women should not take kava because neither its immediate nor its long-term effects on developing babies and infants are known.

Precautions

Individuals who take kava may need to have their liver function monitored.

Taking kava may cause daytime drowsiness, so individuals who need to drive or perform other tasks that require alertness should avoid its use.

What side effects should I watch for?

Major Side Effects

Multiple documented cases of liver damage have been attributed to taking kava. While individuals with previous liver conditions appear to be at highest risk; cases of cirrhosis, hepatitis, liver damage, liver failure, and death have occurred in individuals with no history of liver diseases. In addition, the dose and duration of kava use do not appear to be factors in the development of liver problems. Some individuals who used kava only once or who only took a small amount have developed serious liver problems. Symptoms of liver damage may include:

  • Excessive fatigue
  • Extreme widespread itchiness
  • Nausea, vomiting or diarrhea
  • Pain or swelling in the upper right part of the abdomen
  • Yellowing of the skin or the white parts of the eyes

The unpredictable effect that kava may have on dopamine levels may result in rare cases of uncontrollable movements of the head, mouth, neck, or tongue.

Chronic use of more than 400 mg (0.4 gram)of kava-lactones per day for extended periods of time has resulted in:

  • Blood in the urine
  • Decreased numbers of platelets
  • Decreased numbers of white blood cells
  • Increased numbers of red blood cells
  • Loss of body protein
  • Underweight

Side effects that were seen in a study of individuals who consumed approximately 200,000 mg (200 grams) of kava included:

  • Inability to control muscle movements
  • Shaking
  • Twitches of the eyes

Less Severe Side Effects

Kava has been known to cause upset stomach. Individuals taking kava have also reported central nervous system side effects such as dizziness and headaches.

A skin reaction known as "kawaism" has occurred in individuals who consumed large amounts of the kava beverage for extended periods of time. Symptoms of kawaism include dry, rough, yellowish-colored skin and red, irritated eyes.

Kava can cause daytime drowsiness, so individuals who need to drive or perform other tasks that require alertness should avoid its use.

Chewing kava root or drinking kava tea may cause the mouth to become numb.

What interactions should I watch for?

Prescription Drugs

Taking some prescription drugs may increase the risk of liver damage. If kava, which may also result in liver damage, is taken at the same time as a potentially liver-damaging drug, the risk of potentially life threatening liver damage may increase even more. Drugs that may possibly damage the liver include:

  • Anticonvulsants such as carbamazepine and valproic acid
  • Antifungal drugs such as itraconazole, ketoconazole, and Lamisil
  • Antiviral drugs such as nevirapine (Viramune) and ritonavir (Norvir)
  • Arava
  • azathioprine
  • Cholesterol-lowering drugs (fibric acid derivatives) such as fenofibrate (Tricor) and gemfibrozil (Lopid)
  • Cholesterol-lowering drugs (statins) such as Lipitor, lovastatin, pravastatin, and simvastatin
  • Cognex
  • isoniazid
  • methotrexate
  • Oral drugs for diabetes (glitazones) such as Actos) and Avandia
  • Precose
  • rifampin
  • tamoxifen

When kava is used with prescription drugs that promote sleepiness, the effects of the drug may be exaggerated, resulting in sedation or mental impairment. Prescription drugs that can cause sleepiness include:

  • Anticonvulsants such as carbamazepine, phenytoin and valproic acid
  • Barbiturates such as phenobarbital
  • Benzodiazepines such as alprazolam and diazepam
  • Drugs for insomnia such as zaleplon and zolpidem
  • Tricyclic antidepressants such as amitriptyline, amoxapine, doxepin and nortriptyline

In laboratory studies, kava has been shown to increase the time blood needs to clot. When it is taken with antiplatelet or anticoagulant drugs, the effect of the drug may be increased, possibly resulting in uncontrolled bleeding.

  • Antiplatelets include clopidogrel and Ticlid
  • Anticoagulants include heparin and warfarin

Because it is broken down by certain enzymes in the liver, kava may possibly interfere with the use of prescription drugs that are processed by the same enzymes. Some of these drugs are:

  • Allergy drugs such as fexofenadine (Allegra)
  • Antifungal drugs such as itraconazole and ketoconazole
  • Cancer drugs such as etoposide, paclitaxel, vinblastine, or vincristine
  • Drugs for high cholesterol such as lovastatin
  • Oral contraceptives

Kava's potential to alter dopamine levels may interfere with the effectiveness of drugs such as carbidopa-levodopa (Sinemet), levodopa (Dopar), Mirapex, Requip, and selegiline (Eldepryl), which mainly are used to treat Parkinson's disease.

Non-prescription Drugs

Rarely, some drugs that are sold without a prescription may cause damage to the liver. If these drugs are taken at the same time as kava, the risk of liver damage may increase. Non-prescription drugs that may be associated with liver damage include niacin (vitamin B-3) and antifungal drugs such as ketoconazole (Nizoral) and terbinafine (Lamisil).

The sleep-producing effects of over-the-counter products containing diphenhydramine or doxylamine may be enhanced by taking kava at the same time. Diphenhydramine and doxylamine are contained in many non-prescription sleeping pills as well as in some cough and cold products, therefore caution should be used when taking these medications with kava because excessive drowsiness may result.

Kava may affect the ability of blood to clot after an injury. Aspirin can also delay clotting, so kava should not be taken orally at the same time as aspirin.

Herbal Products

If it is taken at the same time as other herbal products or dietary supplements that could affect liver function, kava might increase the chance of liver problems. Other herbs and supplements that may affect liver function include:

  • Borage
  • Comfrey
  • DHEA
  • Pennyroyal Oil
  • Scullcap
  • Uva Ursi
  • Valerian

Kava may cause excessive sedation if it is taken with other potentially sedating herbs or supplements such as:

  • Catnip
  • Hops
  • St. John's Wort
  • Tryptophan
  • Valerian

Theoretically, if kava is used with other herbs that affect blood clotting, bleeding may occur. Some of the most common herbal products that might inhibit blood clotting are:

  • Danshen
  • Devil's Claw
  • Eleuthero
  • Garlic
  • Ginger (in high amounts)
  • Ginkgo
  • Horse Chestnut
  • Panax Ginseng
  • Papain

One case report suggests that kava’s potential liver toxicity may be increased by St. John’s wort. Therefore, the two herbals should not be used at the same time.

Foods

Drinking alcohol at the same time as using kava by mouth may result in increased drowsiness.

Some interactions between herbal products and medications can be more severe than others. The best way for you to avoid harmful interactions is to tell your doctor and/or pharmacist what medications you are currently taking, including any over-the-counter products, vitamins, and herbals. For specific information on how kava interacts with drugs, other herbals, and foods and the severity of those interactions, please use our Drug Interactions Checker to check for possible interactions.

Should I take it?

Kava is a member of the pepper family of plants that grows mainly in the tropical climate of islands in the South Pacific Ocean. Traditionally, it has been used to prepare a ceremonial drink that promotes feelings of well-being — much as alcoholic beverages are used in social settings.

Kava plants grow as tall perennial bushes with broad, flat heart-shaped leaves. Although the plants produce small flowers, they do not produce seeds that will sprout. They spread by sending out rhizomes — fleshy extensions of their stems that run just under the ground and produce new plants. Generally, the roots of kava plants that are 3 years to 4 years old are harvested to make the traditional beverage as well as for medicine. For farming, cuttings are taken of the kava stems when the roots are dug up. One kava stem may produce several new plants. Young kava plants need protection from the sun and the wind, so they are often planted between rows of taller plants such as banana trees or sweet potatoes.

In the South Pacific, the kava beverage traditionally was prepared in a formalized ritual similar to the Japanese tea-preparation ceremony. In some parts of the area, only certain individuals were authorized to make the beverage, which not every member of the group was allowed to drink. Although the details of the ceremonies may differ by region, a typical process involves chewing kava or wrapping dried and shredded kava root into a cloth “ball” which is dipped into a container of water until it is thoroughly waterlogged. Then, the water is squeezed out of the ball back into the container. The whole dunking and squeezing process is repeated until the water assumes a slightly thick, cloudy appearance – a few minutes to about half an hour depending on the location. Now, although traditional ways are still observed in some places, kava beverages are often made from dried, powdered kava in electric blenders. Either way, the resulting beverage, which is said to look like mud or dirty dishwater, has a taste described as slightly bitter and peppery.

Dosage and Administration

Until re-evaluations of kava's safety are completed by the FDA and the WHO, the use of kava is not recommended.

Note: As treatment for anxiety, kava may take up to 2 months to reach maximum effectiveness.

Note: Many of the human studies of kava used a preparation that was standardized to contain 70% kava lactones. Most of the kava products that were on the market before they were recalled were approximately one-half as concentrated. Standardization by the manufacturer should assure the same amount of active ingredient in every batch of the commercial preparation. Standardization of herbal products is not required by the FDA, so not every kava product that was previously available in the U.S. contained the same amounts of active ingredients.


Summary

Due to its association with cases of liver damage, the oral use of kava is discouraged.

Risks

Because it may worsen liver conditions and Parkinson's disease, kava should be avoided by individuals with those conditions. Pregnant and breast-feeding women should not take it because its possible effects in developing babies and infants are not known.

Side Effects

Deaths and serious liver damage have been attributed to taking kava. It is also suspected of causing rare instances of changes in blood cell numbers, weight loss, shaking, and uncontrollable body movements. A characteristic skin condition known as kawaism or kava dermopathy may result from large doses of kava taken for long periods of time. Kava has also been associated with dizziness, drowsiness, headaches, stomach upset, and numbness of the mouth.

Interactions

Potentially, kava may interact with alcohol and many drugs or herbals that affect liver function, promote sleep, lessen blood clotting, treat Parkinson's disease, or break down in the liver.

Last Revised September 20, 2006

References

Abraham KC, Connor KM, Davidson JR. Explanatory attributions of anxiety and recovery in a study of kava. Journal of Alternative and Complementary Medicine. 2004;10(3):556-559.

Anke J, Ramzan I. Kava Hepatotoxicity: Are we any closer to the truth? Planta Medica. 2004;70(3):193-196.

Anke J, Ramzan I. Pharmacokinetic and pharmacodynamic drug interactions with Kava (Piper methysticum Forst. f.). Journal of Ethnopharmacology. 2004;93(2-3):153-160.

Anon: Kava. In: DerMarderosian A, Beutler JA, eds. Facts and Comparisons: The Review of Natural Products. St. Louis, MO, Facts and Comparisons. December 1999.

Anon. Hepatic toxicity possibly associated with kava-containing products-United States, Germany, Switzerland, 1999-2002. Morbidity and Mortality Weekly Report. 2002;51(47):1065-1067.

Baum SS, Hill R, Rommelspacher H. Effect of kava extract and individual kavapyrones on neurotransmitter levels in the nucleus accumbens of rats. Progress in Neuropsychopharmacology, Biology, and Psychiatry. 1998;22(7):1105-1120.

Bilia AR, Gallori S, Vincieri FF. Kava-kava and anxiety: growing knowledge about the efficacy and safety. Life Sciences. 2002;70(22):2581-2597.

Block KI, Gyllenhaal C, Mead MN. Safety and efficacy of herbal sedatives in cancer care. Integrated Cancer Therapy. 2004;3(2):128-148.

Boerner RJ, Sommer H, Berger W, Kuhn U, Schmidt U, Mannel M. Kava-Kava extract LI 150 is as effective as opipramol and buspirone in generalised [sic] anxiety disorder--an 8-week randomized, double-blind multi-centre clinical trial in 129 out-patients. Phytomedicine. 2003;10(Suppl 4):38-49.

Blumenthal M. German government reconsiders kava. HerbalGram. American Botanical Council. Available at: http://www.herbalgram.org/default.asp?c=kava_overturn. Accessed October 19, 2006.

Bressler R. Herb-drug interactions: interactions between kava and prescription medications. Geriatrics. 2005;60(9):24-25.

Cairney S, Maruff P, Clough AR. The neurobehavioural effects of kava. Australia and New Zealand Journal of Psychiatry. 2002;36(5):657-662.

Cairney S, Maruff P, Clough AR, Collie A, Currie J, Currie BJ. Saccade and cognitive impairment associated with kava intoxication. Human Psychopharmacology. 2003;18(7):525-533.

Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration. Consumer advisory. Kava-containing dietary supplements may be associated with severe liver injury. March 25, 2002.

Clouatre DL. Kava kava: examining new reports of toxicity. Toxicology Letter. 2004;150(1):85-96.

Clough AR, Rowley K, O'Dea K. Kava use, dyslipidaemia [sic] and biomarkers of dietary quality in Aboriginal people in Arnhem Land in the Northern Territory (NT), Australia. European Journal of Clinical Nutrition. 2004;58(7):1090-1093.

Committee on Safety of Medicines. Medicines and Healthcare Products Regulatory Agency. Kava-kava and hepatotoxicity. Current Problems in Pharmacovigilance. 2003;29:8. Available at: http://www.medicines.mhra.gov.uk/ourwork/monitorsafequalmed/currentproblems/cpsept2003.pdf. Accessed September 29, 2003.

Connor KM, Payne V, Davidson JR. Kava in generalized anxiety disorder: three placebo-controlled trials. International Clinical Psychopharmacology. 2006;21(5):249-253.

Dasgupta A, Bernard DW. Herbal remedies: effects on clinical laboratory tests. Archives of Pathology and Laboratory Medicine. 2006;130(4):521-528.

Davies LP, Drew CA, Duffield P, Johnston GA, Jamieson DD. Kava pyrones and resin: studies on GABA-A, GABA-B, and benzodiazepine binding sites in rodent brain. Pharmacology and Toxicology. 1992;71(2):120-126.

Denham A, McIntyre M, Whitehouse J. Kava--the unfolding story: report on a work-in-progress. Journal of Alternative and Complementary Medicine. 2002;8(3):237-263.

Ernst E. Herbal remedies for anxiety - a systematic review of controlled clinical trials. Phytomedicine. 2006;13(3):205-208.

Folmer F, Blasius R, Morceau F, et al. Inhibition of TNFalpha-induced activation of nuclear factor kappaB by kava (Piper methysticum) derivatives. Biochemistry and Pharmacology. 2006;71(8):1206-1218.

Foster S. Kava. Piper methysticum. 2000. Available at: http://www.stevenfoster.com/education/monograph/kava.html. Accessed December 8, 2003.

Garner LF, Klinger JD. Some visual effects caused by the beverage kava. Journal of Ethnopharmacology. 1985;13(3):307-311.

Geier FP, Konstantinowicz T. Kava treatment in patients with anxiety. Phytotherapy Research. 2004;18(4):297-300.

Gleitz J, Beile A, Wilkens P, Ameri A, Peters T. Antithrombotic action of the kava pyrone (+)-kavain prepared from Piper methysticum on human platelets. Planta Medica. 1997;63(1):27-30.

Government of Samoa. Department of Trade, Commerce and Industry. Trade and Investment Promotion Unit. Investing in the agriculture sector In Samoa. Project report: kava. 1998. Available at: http://www.sptc.gov.au/ausint/pdf/sm_kava-production.pdf. Accessed December 8, 2003.

Gow PJ, Connelly NJ, Hill RL, Crowley P, Angus PW. Fatal fulminant hepatic failure induced by a natural therapy containing kava. Medical Journal of Australia. 2003;178(9):442-443.

Gruenwald J, Mueller C, Skrabal J. Kava report 2003. In-depth investigation into EU member states market restrictions on kava products. March 2003. Brussels, Belgium. Center for the Development of Enterprise. Available at: http://www.analyze-realize.com/Papers/KavaReport2003.pdf. Accessed December 8, 2003.

Gurley BJ, Gardner SF, Hubbard MA, et al. In vivo effects of goldenseal, kava kava, black cohosh, and valerian on human cytochrome P450 1A2, 2D6, 2E1, and 3A4/5 phenotypes. Clinical Pharmacology and Therapeutics. 2005;77(5):415-426.

Health Canada. Health Canada issues a stop-sale order for all products containing kava. Health Canada Advisory. August 21, 2002. Available at: http://www.hc-sc.gc.ca/english/protection/warnings/2002/2002_56e.htm. Accessed September 8, 2004.

Health Canada. Health Canada reminds Canadians not to use products containing kava. Health Canada Advisory. December 23, 2003. Available at: http://www.hc-sc.gc.ca/english/protection/warnings/2003/2003_103.htm. Accessed September 8, 2004.

Heinze HJ, Munthe TF, Steitz J, Matzke M. Pharmacopsychological effects of oxazepam and kava-extract in a visual search paradigm assessed with event-related potentials. Pharmacopsychiatry. 1994;27(6):224-230.

Humberston CL, Akhtar J, Krenzelok EP. Acute hepatitis induced by kava kava. Journal of Toxicology and Clinical Toxicology. 2003;41(2):109-113.

Huntley AL, Ernst E. A systematic review of herbal medicinal products for the treatment of menopausal symptoms. Menopause. 2003;10(5):465-476.

Izzo AA, Ernst E. Interactions between herbal medicines and prescribed drugs: a systematic review. Drugs. 2001;61(15):2163-2175.

Jacobs BP, Bent S, Tice JA, Blackwell T, Cummings SR. An internet-based randomized, placebo-controlled trial of kava and valerian for anxiety and insomnia. Medicine (Baltimore). 2005;84(4):197-207.

Jellin JM, Gregory P, Batz F, Hitchens K, et al, eds. Pharmacist's Letter/Prescriber's Letter. Natural Medicines Comprehensive Database, 3rd Edition. Stockton CA: Therapeutic Research Facility, 2000.

Jhoo JW, Freeman JP, Heinze TM, et al. In vitro cytotoxicity of nonpolar constituents from different parts of kava plant (Piper methysticum). Journal of Agricultural and Food Chemistry. 2006;54(8):3157-3162.

Jussofie A, Schmiz A, Hiemke C. Kavapyrone [sic] enriched extract from Piper methysticum as modulator of the GABA binding site in different regions of rat brain. Psychopharmacology. 1994;116(4):469-474.

Lehrl S. Clinical efficacy of kava extract WS 1490 in sleep disturbances associated with anxiety disorders. Results of a multicenter, randomized, placebo-controlled, double-blind clinical trial. Journal of Affective Disorders. 2004;78(2):101-110.

Loew D, Franz G. Quality aspects of traditional and industrial Kava-extracts. Phytomedicine. 2003;10(6-7):610-612.

Malsch U, Kieser M. Efficacy of kava-kava in the treatment of non-psychotic anxiety, following pretreatment with benzodiazepines. Psychopharmacology. (Berlin) 2001;157(3):277-283.

Mathews JD, Riley MD, Fejo L, et al. Effects of heavy usage of kava on physical health: Summary of a pilot survey in an aboriginal community. Medical Journal of Australia. 1988;148(11):548-555.

Mathews JM, Etheridge AS, Black SR. Inhibition of human cytochrome P450 activities by kava extract and kavalactones [sic]. Drug Metabolism and Disposition. 2002;30(11):1153-1157.

Mathews JM, Etheridge AS, Valentine JL, et al. Pharmacokinetics and disposition of the kavalactone kawain: interaction with kava extract and kavalactones in vivo and in vitro. Drug Metabolism and Disposition. 2005;33(10):1555-1563.

Mayell M. Methods of preparation, kava root. In: Natural Energy: A Consumer’s Guide to Legal, Mind-altering, and Mood-brightening Herbs and Supplements. New York: Three Rivers Press. 1998.

McAvoy A. Island elixir kava is making a comeback. Ventura County Star. October 15, 2006.

Meijerman I, Beijnen JH, Schellens JH. Herb-drug interactions in oncology: focus on mechanisms of induction. Oncologist. 2006;11(7):742-752.

Meseguer E, Taboada R, Sanchez V, Mena MA, Campos V, Garcia De Yebenes J. Life-threatening parkinsonism induced by kava-kava. Movement Disorders. 2002;17(1):195-196.

Mills E, Singh R, Ross C, Ernst E, Ray JG. Sale of kava extract in some health food stores. Canadian Medical Association Journal. 2003;169(11):1158-1159.

Moulds RF, Malani J. Kava: herbal panacea or liver poison? Medical Journal of Australia. 2003;178(9):451-453.

Munte TF, Heinze HJ, Matzke M, Steitz J. Effects of oxazepam and an extract of kava roots (Piper methysticum) on event-related potentials in a word recognition task. Neuropsychobiology. 1993;27(1):46-53.

Musch E, Chrissafidou A, Malek M. Acute hepatitis due to kava-kava and St John's Wort: an immune-mediated mechanism? [Article in German] Deutsche Medizinische Wochenschrift. 2006;131(21):1214-1217.

Norton SA, Ruze P. Kava dermopathy. Journal of the American Academy of Dermatology. 1994;31(1):89-97.

Osborne T. Pacific kava. A producer’s guide. 2001. Suva, Fiji. Secretariat of the Pacific Community.

Peirce A. The American Pharmaceutical Association Practical Guide to Natural Medicines. New York: The Stonesong Press, 1999.

Pittler MH, Ernst E. Kava extract for treating anxiety. Cochrane Database Systemic Review. 2003;(1):CD003383.

Pittler MH, Ernst E. Efficacy of kava extract for treating anxiety: systematic review and meta-analysis. Journal of Clinical Psychopharmacology. 2000;20(1):84-89.

Pollock NJ. Sustainability of kava trade. Victoria University, Wellington, New Zealand. November 19, 2000. Available at: http://www.devnet.org.nz/conf/Papers/pollock.pdf. Accessed December 8, 2003.

Russmann S, Barguil Y, Cabalion P, Kritsanida M, Duhet D, Lauterburg BH. Hepatic injury due to traditional aqueous extracts of kava root in New Caledonia. European Journal of Gastroenterology and Hepatology. 2003;15(9):1033-1036.

Ruze P. Kava-induced dermopathy: a niacin deficiency? Lancet 1990;335(8703):1442-1445.

Schulze J, Raasch W, Siegers CP. Toxicity of kava pyrones, drug safety and precautions--a case study. Phytomedicine. 2003;10(Suppl 4):68-73.

Seitz U, Schule A, Gleitz J. [3H]-monoamine uptake inhibition properties of kava pyrones. Planta Medica. 1997;63(6):548-549.

Singh YN. Effects of kava on neuromuscular transmission and muscle contractility. Journal of Ethnopharmacology. 1983;7(3):267-276.

Singh YN. Kava: an overview. Journal of Ethnopharmacology. 1992;37(1):13-45.

Singh YN. Potential for interaction of kava and St. John's wort with drugs. Journal of Ethnopharmacology. 2005;100(1-2):108-113.

Sorrentino L, Capasso A, Schmidt M. Safety of ethanolic kava extract: Results of a study of chronic toxicity in rats. Phytomedicine. 2006;13(8):542-549.

Sparreboom A, Cox MC, Acharya MR, Figg WD. Herbal remedies in the United States: potential adverse interactions with anticancer agents. Journal of Clinical Oncology. 2004;22(12):2489-2503.

Spinella M. Herbal Medicines and Epilepsy: The Potential for Benefit and Adverse Effects. Epilepsy and Behavior. 2001;2(6):524-532.

Steiner GG. The correlation between cancer incidence and kava consumption. Hawaii Medical Journal. 2000;59(11):420-422.

Stickel F, Baumuller HM, Seitz K, et al. Hepatitis induced by Kava (Piper methysticum rhizoma). Journal of Hepatology. 2003;39(1):62-67.

Teschke R, Gaus W, Loew D. Kava extracts: safety and risks including rare hepatotoxicity. Phytomedicine. 2003;10(5):440-446.

Thompson R, Ruch W, Hasenohrl RU. Enhanced cognitive performance and cheerful mood by standardized extracts of Piper methysticum (Kava-kava). Human Psychopharmacology. 2004;19(4):243-250.

Ulbricht C, Basch E, Boon H, et al. Safety review of kava (Piper methysticum) by the Natural Standard Research Collaboration. Expert Opinion on Drug Safety. 2005;4(4):779-794.

Unger M, Holzgrabe U, Jacobsen W, Cummins C, Benet LZ. Inhibition of cytochrome P450 3A4 by extracts and kavalactones [sic] of Piper methysticum (Kava-Kava). Planta Medica. 2002;68(12):1055-1058.

Volz HP, Kieser M. Kava-kava extract WS 1490 versus placebo in anxiety disorders--a randomized placebo-controlled 25-week outpatient trial. Pharmacopsychiatry. 1997;30(1):1-5.

Weiss J, Sauer A, Frank A, Unger M. Extracts and kavalactones of Piper methysticum G. Forst (kava-kava) inhibit P-glycoprotein in vitro. Drug Metabolism and Disposition. 2005;33(11):1580-1583.

Werneke U, Earl J, Seydel C, Horn O, Crichton P, Fannon D. Potential health risks of complementary alternative medicines in cancer patients. British Journal of Cancer. 2004;90(2):408-413.

Whitton PA, Lau A, Salisbury A, Whitehouse J, Evans CS. Kava lactones and the kava-kava controversy. Phytochemistry. 2003;64(3):673-679.

Witte S, Loew D, Gaus W. Meta-analysis of the efficacy of the acetonic kava-kava extract WS1490 in patients with non-psychotic anxiety disorders. Phytotherapy Research. 2005;19(3):183-188.

World Health Organization. WHO to investigate kava ban. [Press release] December 3, 2003.

World Wildlife Fund. Piper methysticum. No date given. Available at: http://www.wwf.org.uk/filelibrary/pdf/pmethysticum.pdf. Accessed December 8, 2003.

Wu D, Yu L, Nair MG, DeWitt DL, Ramsewak RS. Cyclooxygenase enzyme inhibitory compounds with antioxidant activities from Piper methysticum (kava kava) roots. Phytomedicine. 2002;9(1):41-47.

Zi X, Simoneau AR. Flavokawain A, a novel chalcone from kava extract, induces apoptosis in bladder cancer cells by involvement of Bax protein-dependent and mitochondria-dependent apoptotic pathway and suppresses tumor growth in mice. Cancer Research. 2005;65(8):3479-3486.

Zou L, Harkey MR, Henderson GL, Dike LE. Kava does not display metabolic toxicity in a homogeneous cellular assay. Planta Medica. 2004;70(4):289-292.

Last Revised September 20, 2006

Note: The above information is not intended to replace the advice of your physician, pharmacist, or other healthcare professional. It is not meant to indicate that the use of the product is safe, appropriate, or effective for you.

In general, herbal products are not subject to review or approval by the U.S. Food and Drug Administration (FDA). They are not required to be standardized, meaning that the amounts of active ingredients or contaminants they contain may vary between brands or between different batches of the same brand. Not all of the risks, side effects, or interactions associated with the use of herbal products are known because few reliable studies of their use in humans have been done.

This information is provided for your education only. Please share this information with your healthcare provider and be sure that you talk to your doctor and pharmacist about all the prescription and non-prescription medicines you take before you begin to use any herbal product.

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