Kava
Summary
Kava extract eased anxiety symptoms more than placebo in a Cochrane review of 11 trials (grade B), but a 16-week trial in generalized anxiety disorder found no benefit. Rare but severe liver injury, including liver failure and transplants, led the FDA to issue a 2002 consumer advisory. Kava should not be combined with alcohol or sedatives.
Key facts
- The root of a South Pacific pepper plant, used as a traditional drink and as extracts standardized to kavalactones[2][13]
- Anxiety symptoms (B, short-term trials); generalized anxiety disorder (mixed: one positive 6-week trial, one null 16-week phase III trial)[4][5][6]
- March 2002: kava supplements may be associated with severe liver injury, including hepatitis, cirrhosis and liver failure[1]
- CDC counted 11 kava users with liver failure who needed transplants in Germany, Switzerland and the US (1999–2002)[3]
- 120–240 mg/day of kavalactones in recent trials; 150–300 mg/day of the extract WS 1490 in older trials[5][6][8]
- NCCIH: avoid kava with alcohol, benzodiazepines or other sedating substances[2]
- Can cause kava dermopathy: dry, scaly skin, red eyes and temporary yellowing of skin, hair and nails[2]
- 5 graded human outcomes on this page
- October 10, 2026
How it works
ProposedKavalactones (kavapyrones) are thought to act on brain signalling involved in anxiety; in trials, response was linked to GABA transporter gene variants, but the mechanism is not established.[5][13]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Anxiety symptoms (Hamilton Anxiety scale) | Improved | Grade B | Meta-analysis · n = 645 · 2003 Adults with anxiety in 11 double-blind placebo-controlled trials Form: Kava extract (single-ingredient products) · Dose: Varied across trials · Duration: 1–24 weeks In 6 trials (345 people) the Hamilton Anxiety score fell 5.0 points more with kava than placebo; adverse events in the trials were mild, transient and infrequent. | 12535473 (opens PubMed)Source [4] |
| Anxiety disorders over 25 weeks | Improved | Grade C | RCT · n = 101 · 1997 Outpatients with non-psychotic anxiety disorders Form: Kava extract WS 1490 · Dose: Not stated in the abstract · Duration: 25 weeks Hamilton Anxiety scores improved more than placebo from week 8 on; adverse events were rare and evenly distributed. | 9065962 (opens PubMed)Source [7] |
| Generalized anxiety disorder (6 weeks) | Improved | Grade C | RCT · n = 58 · 2013 Adults with GAD and no mood disorder Form: Aqueous kava root extract · Dose: 120–240 mg/day of kavalactones · Duration: 6 weeks Anxiety fell more with kava than placebo (effect size 0.62); 26% versus 6% remitted. More headaches on kava; liver tests did not differ. | 23635869 (opens PubMed)Source [5] |
| Anxiety, tension and restlessness in general practice | Mixed | Grade D | RCT · n = 141 · 2003 Adult outpatients with neurotic anxiety Form: Kava extract WS 1490 · Dose: 150 mg/day (50 mg three times daily) · Duration: 4 weeks End-of-treatment anxiety scores did not differ significantly, but an exploratory analysis of change favoured kava; well-being and global ratings improved. Liver tests were unaffected. | 14692723 (opens PubMed)Source [8] |
| Generalized anxiety disorder (16 weeks) | No effect | No effect | RCT · n = 171 · 2020 Adults with GAD not taking medication Form: Aqueous kava root extract tablets · Dose: 120 mg of kavalactones twice daily · Duration: 16 weeks No significant difference from placebo (difference of 1.37 points favouring placebo); 17.4% remitted on kava versus 23.8% on placebo. Memory problems, tremor and abnormal liver tests were more frequent on kava, though no one met criteria for herb-induced liver injury. | 31813230 (opens PubMed)Source [6] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Aqueous (water-based) kava root extract | Varies[5][6] | No human absorption data in our sources.[5] | Headaches in a 6-week trial; memory problems, tremor and more abnormal liver tests in a 16-week trial.[5][6] | Generalized anxiety disorder (120–240 mg/day kavalactones) |
| Acetone or ethanol kava extracts (e.g., WS 1490) | Varies[7][8][13] | No human absorption data in our sources.[13] | The first liver injury reports involved alcohol- or acetone-extracted products; trials reported few adverse events.[2][8] | Anxiety disorders (150–300 mg/day extract) |
| Traditional kava beverage | Varies[2] | No human absorption data in our sources.[2] | Some liver injury cases involved kava drinks prepared with water.[2] | Ceremonial and social use; not the form in most trials |
Studied doses
Doses studied in human trials ranged from 120 to 240 mg/day of kavalactones for 6 to 16 weeks, and 150 to 300 mg/day of the extract WS 1490 for 4 to 25 weeks; trials in the Cochrane review lasted 1 to 24 weeks.[5][6][8][4]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
Medicines
- Benzodiazepines and other sedativesNIH fact sheetNCCIH advises against combining kava with other sedating substances such as benzodiazepines.[2]
- AlcoholNIH fact sheetNCCIH advises against combining kava with alcohol; alcohol is often present in reported cases of kava liver injury.[2][11]
- Medicines that can affect the liverFDA safety communicationFDA advised people taking drugs that can affect the liver to consult a physician before using kava supplements.[1]
- Drugs metabolized by CYP450 enzymesReviewSeveral kavalactones inhibit these enzymes in the lab, so interactions are possible; clinical evidence is limited.[10]
Who should be careful
- Liver disease or liver problems
- FDA advised people with liver disease or liver problems to consult a physician before using kava supplements because of severe liver injury reports.[1]
- Alcohol and sedative users
- Kava should not be combined with alcohol, benzodiazepines or other sedating substances.[2]
- Pregnancy and breastfeeding
- NCCIH says kava may carry special risks in pregnancy and breastfeeding because of harmful pyrone constituents.[2]
- Long-term or high-dose use
- Prolonged use and overdose were risk factors in assessed liver injury cases, and long-term high doses can cause kava dermopathy.[9][2]
- Anyone with signs of liver trouble
- Jaundice, brown urine, light stools, nausea, unusual tiredness or abdominal pain while using kava warrant medical attention, per FDA.[1]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Liver safety: the kava hepatotoxicity history
Rare but sometimes severe or fatal liver injury has been linked to kava products.
- 1999–2002: case reports
- Health professionals in Germany, Switzerland and the US reported severe liver toxicity; 11 kava users had liver failure and needed transplants.[3]
- March 2002: FDA advisory
- FDA warned that kava supplements may be associated with severe liver injury, citing over 25 reports abroad (four transplants) and a US transplant in a previously healthy young woman, after Germany, Switzerland, France, Canada and the UK acted.[1]
- Causality assessment
- In 14 assessed cases, causality was highly probable in 1, probable in 4 and possible in 9; overdose, prolonged use and other medicines or supplements were common risk factors, and injury occurred with water, ethanol and acetone extracts alike.[9]
- German ban reversed
- Germany banned ethanolic and acetonic kava extracts in 2002; administrative courts later found the ban inappropriate, and the regulator did not appeal.[9][12]
- Current view
- NCCIH lists possible contributors: poor cultivars or plant parts, alcohol, adulteration, genetics, and large or prolonged use.[2]
- Recent trial data
- In the 16-week GAD trial, abnormal liver tests were more frequent on kava, although no participant met criteria for herb-induced liver injury.[6]
How to read the label
- Label dose vs clinical doseRecent trials used 120–240 mg/day of kavalactones from an aqueous extract; older trials used 150–300 mg/day of the extract WS 1490. Labels may list extract weight rather than kavalactones.[5][6][8]
- Extraction methodThe first liver injury cases involved alcohol- or acetone-extracted products, but later cases involved water-based drinks too.[2]
- Plant part and qualityKava products vary greatly with the plant parts extracted and the extraction method; substandard products may cause or worsen adverse effects.[13]
- Names on labelsFDA lists names for kava on Supplement Facts panels, including ava, awa, kawa, sakau, yangona and Piper methysticum.[1]
Frequently asked questions
Does kava help anxiety?
A Cochrane review of 11 trials lasting 1–24 weeks found anxiety scores about 5 points lower than placebo, but a 16-week trial in generalized anxiety disorder found no benefit.[4][6]
Is kava bad for your liver?
Rare but severe liver injury, including liver failure needing transplants, has been reported; the FDA issued a consumer advisory in 2002.[1][3]
Is kava banned?
Germany banned ethanolic and acetonic kava extracts in 2002, but courts later overturned the ban. In the US, FDA issued a consumer advisory.[9][12][1]
Can I drink alcohol with kava?
NCCIH advises against combining kava with alcohol or sedatives, and alcohol is common in reported liver injury cases.[2][11]
What are the side effects of kava?
Digestive upset, headache, dizziness and, with long-term heavy use, kava dermopathy; trials also reported memory problems and tremor.[2][6]
Is kava safe in pregnancy?
NCCIH says kava may have special risks during pregnancy and breastfeeding because of harmful pyrone constituents.[2]
Sources
- [1]Consumer Advisory: Kava-Containing Dietary Supplements May be Associated With Severe Liver Injury (March 25, 2002; archived FDA page). U.S. Food and Drug Administration, 2002. safety-communication
- [2]Kava: Usefulness and Safety (last updated April 2025). National Center for Complementary and Integrative Health (NCCIH), 2025. fact-sheet
- [3]Hepatic toxicity possibly associated with kava-containing products--United States, Germany, and Switzerland, 1999-2002.. MMWR Morb Mortal Wkly Rep, 2002. observational
- [4]Kava extract for treating anxiety.. Cochrane Database Syst Rev, 2003. meta-analysis
- [5]Kava in the treatment of generalized anxiety disorder: a double-blind, randomized, placebo-controlled study.. J Clin Psychopharmacol, 2013. RCT
- [6]Kava for generalised anxiety disorder: A 16-week double-blind, randomised, placebo-controlled study.. Aust N Z J Psychiatry, 2020. RCT
- [7]Kava-kava extract WS 1490 versus placebo in anxiety disorders--a randomized placebo-controlled 25-week outpatient trial.. Pharmacopsychiatry, 1997. RCT
- [8]Treatment of anxiety, tension and restlessness states with Kava special extract WS 1490 in general practice: a randomized placebo-controlled double-blind multicenter trial.. Phytomedicine, 2003. RCT
- [9]Kava hepatotoxicity--a clinical review.. Ann Hepatol, 2010. review
- [10]Pharmacokinetic and pharmacodynamic drug interactions with Kava (Piper methysticum Forst. f.).. J Ethnopharmacol, 2004. review
- [11]Role of ethanol in kava hepatotoxicity.. Phytother Res, 2010. review
- [12]German Kava Ban Lifted by Court: The Alleged Hepatotoxicity of Kava (Piper methysticum) as a Case of Ill-Defined Herbal Drug Identity, Lacking Quality Control, and Misguided Regulatory Politics.. Planta Med, 2015. review
- [13]The Pharmacology, Pharmacokinetics, Efficacy, and Adverse Events Associated With Kava.. J Clin Pharmacol, 2018. review
What changed
- First draft. Every PMID checked against NCBI E-utilities esummary (title and year taken from the record) and abstracts read for the cited rows.
- Adversarial review pass: every evidence row re-read against its PubMed abstract. Official sources opened before citing: FDA consumer advisory of March 25, 2002 (archived FDA page, linked from the ODS kava page), NCCIH Kava fact sheet (April 2025), ODS kava resources page (which also links the FDA August 2020 literature memo and the CDC MMWR report). No ODS fact sheet or EMA monograph exists for kava. Safety-first page per the queue flag: hepatotoxicity history (case reports, FDA advisory, causality assessment, German court ruling) carried in safetyFocus; no product links. Industry ties: the WS 1490 extract trials (1997, 2003) list no funding or COI in PubMed (not in PMC); the 2013 and 2020 GAD trials list no COI in PubMed (not in PMC). The 2001 and 2002 Cochrane versions carry UpdateIn flags and are superseded by the cited 2003 version. Retraction, expression-of-concern, erratum and withdrawn checks on all 11 PMIDs: none flagged. Page set indexable. Independent browser review (4 parallel reviewers, every evidence row checked against its abstract and official sources on the Vercel preview) found: no issues (hepatotoxicity history, FDA advisory and NCCIH claims verified; no product links).