Herb & supplement monograph

Kava Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS ·Updated July 2026

What is this page for?

First and foremost: how Kava interacts with medications. The heart of this page is the interaction list — every drug Kava is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Kava is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Kava Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, Kava drug interactions carry a moderate overall risk of being clinically significant, and the risk rises considerably for anyone who takes sedating medicines or drinks alcohol. Hundreds of the listed interactions are rated major or moderate, and kava's best-documented effect, added sedation, is backed by human evidence.

Interactions deserving the most attention

The clearest concern is with CNS depressants such as sedatives, sleep medicines, and other calming drugs, where kava can add to drowsiness and slow reflexes. Combining kava with alcohol may increase both sedation and strain on the liver, since kava itself has been linked to over 100 reports of liver injury; similar caution applies to other medicines that can stress the liver. A human study also found kava slows one enzyme the body uses to clear certain medications, which could raise their levels.

What the rest of the list means

The long list of interactions does not mean every combination is harmful. Most entries are theoretical, based on lab research into enzymes and transporters that process medications. In fact, several of those predicted effects were later tested in people and produced no meaningful change, so many listed interactions may never matter in practice.

Check your medications against Kava

Based on HelloPharmacist’s Kava interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Kava

1167 medications have a known interaction with Kava, graded by severity. Select any drug for the full evidence-based detail.

248 major interactions. These combinations can be clinically significant — best avoided, or used only with close professional supervision. Always check with your pharmacist before combining them with Kava.

Don’t want to scroll the list? Just ask.

Tell us the medications you take and we’ll check each one against Kava using our pharmacist-reviewed interaction data.

AI summaries are generated from our Kava interaction data for education only — always confirm with your pharmacist. How we use AI

2,830 drugs

Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
Probable. Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
Possible. Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
Each drug listed above links to the full report for that exact Kava combination — clinical detail, likelihood, evidence level, and citations.
Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

The big picture

The kinds of drugs Kava affects

Every type of medication (drug category) Kava is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 12 drug categories Kava interacts with

Cns DepressantsAlcohol (ethanol)Cytochrome P450 2c19 (cyp2c19) SubstratesCytochrome P450 2c9 (cyp2c9) SubstratesCytochrome P450 2e1 (cyp2e1) SubstratesHaloperidol (haldol)Hepatotoxic DrugsP-glycoprotein SubstratesRopinirole (requip)Cytochrome P450 1a2 (cyp1a2) SubstratesCytochrome P450 2d6 (cyp2d6) SubstratesCytochrome P450 3a4 (cyp3a4) Substrates

Cns Depressants

Combining kava with CNS depressants can have additive sedative effects.
Kava has CNS depressant effects. Concomitant use of kava with other CNS depressants can increase the risk of drowsiness and motor reflex depression. Clinical practice guidelines from a joint taskforce of the World Federation of Societies of Biological Psychiatry (WFSBP) and the Canadian Network for Mood and Anxiety Treatments (CANMAT) recommend that CNS depressants, including alcohol and benzodiazepines, not be used with kava.

Likelihood Probable Evidence A

Alcohol (Ethanol)

Combining kava with alcohol may increase the risk of sedation and/or hepatotoxicity.

Kava has CNS depressant effects. Concomitant use of kava with other CNS depressants can increase the risk of drowsiness and motor reflex depression. Additionally, kava has been associated with over 100 cases of hepatotoxicity. There is some concern that kava can adversely affect the liver, especially when used in combination with hepatotoxic drugs. Clinical practice guidelines from a joint taskforce of the World Federation of Societies of Biological Psychiatry (WFSBP) and the Canadian Network for Mood and Anxiety Treatments (CANMAT) recommend that alcohol not be used with kava.

Likelihood Possible Evidence A

Cytochrome P450 2C19 (Cyp2C19) Substrates

Theoretically, kava might increase levels of CYP2C19 substrates.
In vitro research shows that kava significantly inhibits CYP2C19 enzymes. This effect has not yet been reported in humans.

Likelihood Possible Evidence D

Cytochrome P450 2C9 (Cyp2C9) Substrates

Theoretically, kava might increase levels of CYP2C9 substrates.
In vitro research shows that kava significantly inhibits CYP2C9 enzymes. This effect has not yet been reported in humans.

Likelihood Possible Evidence D

Cytochrome P450 2E1 (Cyp2E1) Substrates

Kava might increase levels of CYP2E1 substrates.
In a clinical study in healthy volunteers, taking kava 1000 mg twice daily (containing a daily dose of 138 mg kavalactones) for 28 days inhibited the metabolism of CYP2E1 substrates.

Likelihood Probable Evidence B

Haloperidol (Haldol)

Combining kava and haloperidol might increase the risk of cardiovascular adverse effects and hypoxia.
Atrial flutter and hypoxia has been reported for a patient who received intramuscular injections of haloperidol and lorazepam after using kava orally. The side effects were attributed to kava-induced inhibition of CYP2D6, but might also have been related to additive adverse effects with the concomitant use of haloperidol, lorazepam, and kava.

Likelihood Possible Evidence D

Hepatotoxic Drugs

Theoretically, using kava with hepatotoxic drugs might increase the risk of liver damage.
Kava has been linked with over 100 cases of hepatotoxicity. Most cases occur with excessive and prolonged use. There is some concern that kava can adversely affect the liver, especially when used in combination with hepatotoxic drugs.

Likelihood Possible Evidence D

P-Glycoprotein Substrates

It is unclear if kava inhibits P-glycoprotein (P-gp); research is conflicting.
In vitro research shows that kava can inhibit P-gp efflux. However, a clinical study in healthy volunteers shows that taking kava standardized to provide 225 mg kavalactones daily for 14 days does not affect the pharmacokinetics of digoxin, a P-gp substrate. It is possible that the use of other P-gp substrates or higher doses of kava might still inhibit P-gp.

Likelihood Possible Evidence D

Ropinirole (Requip)

Taking kava with ropinirole might increase the risk for dopaminergic toxicity.
A case of visual hallucinations and paranoid delusions has been reported for a patient who used kava in combination with ropinirole. The adverse effects were attributed to kava-induced inhibition of CYP1A2, which may have reduced the metabolism of ropinirole, resulting in excessive dopaminergic stimulation.

Likelihood Possible Evidence D

Cytochrome P450 1A2 (Cyp1A2) Substrates

It is unclear if kava inhibits CYP1A2; research is conflicting.
Although in vitro research and a case report suggest that kava inhibits CYP1A2, more robust clinical evidence shows that kava has no effect on CYP1A2. In a clinical study in healthy volunteers, taking kava 1000 mg twice daily (containing a daily dose of 138 mg kavalactones) for 28 days had no effect on CYP1A2 activity.

Likelihood Unlikely Evidence B

Cytochrome P450 2D6 (Cyp2D6) Substrates

It is unclear if kava inhibits CYP1A2; research is conflicting.
In vitro research shows that kava extract significantly inhibits CYP2D6. However, clinical research shows that kava does not affect the metabolism of CYP2D6 substrates in humans.

Likelihood Unlikely Evidence B

Cytochrome P450 3A4 (Cyp3A4) Substrates

It is unclear if kava inhibits CYP3AA; research is conflicting.
Although in vitro research suggests that kava inhibits CYP3A4, more robust clinical evidence shows that kava has no effect on CYP3A4. In a clinical study in healthy volunteers, taking kava 1000 mg twice daily (containing a daily dose of 138 mg kavalactones) for 28 days had no effect on CYP3A4 activity.

Likelihood Unlikely Evidence B

Monograph

Kava: Uses, Safety & Side Effects

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Reviewed July 2026 ·

The bottom line

Kava is a Pacific Island plant traditionally used to promote relaxation and ease anxiety, and some studies suggest it may help mild anxiety. However, kava has been linked to rare but serious liver damage, so it should be used with caution, avoided by people with liver problems, and only used after talking with your pharmacist or doctor.

Scientific name: Piper methysticum
Family: Piperaceae
Part used: Roots and rhizomes
Common forms: Capsules, tablets, liquid extracts, tinctures, teas, and traditional water-based root drinks

People commonly use it for

Anxiety and stress
Restlessness
Trouble sleeping
Relaxation in social or cultural settings
Menopausal symptoms

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance

OverallUse caution

Kava may help anxiety but has been linked to rare, serious liver injury and is banned or restricted in some countries.

PregnancyBest avoided

Kava is not considered safe during pregnancy and should be avoided.

BreastfeedingPossibly Unsafe

When used orally. There is concern that the toxic pyrone constituents of kava can pass into breast milk; avoid using.

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Jump to a section

Overview

Kava (Piper methysticum) is a tropical plant native to the islands of the South Pacific, including Fiji, Vanuatu, Tonga, and Samoa. For hundreds of years, Pacific Island cultures have prepared a drink from the plant's roots and used it during social gatherings, ceremonies, and to help people relax.

The roots contain active compounds called kavalactones, which are thought to be responsible for kava's calming and relaxing effects. Today, kava is sold around the world as a dietary supplement in the form of capsules, liquid extracts, teas, and traditional root preparations. People most often take it hoping to reduce anxiety, ease stress, and unwind.

How it works

Kava's effects are believed to come from a group of compounds called kavalactones. Laboratory and animal research suggests these compounds may act on the brain in ways similar to some calming medications, possibly by affecting GABA, a chemical messenger that helps quiet nerve activity.

Kavalactones may also influence other brain pathways involved in mood, muscle tension, and the body's response to stress. It is important to know that much of this understanding comes from laboratory and animal studies, and scientists do not yet fully understand exactly how kava works in people.

Effectiveness

Does Kava work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by Dr. Brian Staiger, PharmD.

Evidence overview · 10 uses evaluated

1 Leans ineffective 9 Insufficient evidence

How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.

2Likely EffectiveGood evidence, though not yet conclusive.

3Possibly EffectiveSome evidence suggests a benefit.

4Possibly IneffectiveSome evidence it may not help.

5Likely IneffectiveFairly strong evidence it doesn’t help.

6IneffectiveStrong evidence it doesn’t work.

7Insufficient Reliable Evidence to RateToo little research to say either way.

Possibly Ineffective Generalized anxiety disorder (GAD)