Drug & supplement interaction

Kava + Sildenafil

Sildenafil brand name: Revatio.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Sildenafil falls into 2 drug categories that Kava can interact with; the most serious is rated moderate. Theoretically, kava might increase levels of CYP2C9 substrates.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Kava and Sildenafil

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Kava interacts with whole categories of medication. Sildenafil falls into 2 of those categories, so it can interact with Kava in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES

1 of 2

Why this applies to Sildenafil

Sildenafil falls under CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES — the group Kava interacts with.

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.
Severity Moderate Likelihood Possible Evidence D

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.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the gist for sildenafil (Viagra or Revatio). Your body uses a liver enzyme called CYP2C9 to help clear sildenafil out. Lab studies suggest kava can slow that enzyme down. If that happened in a real person, sildenafil could hang around longer and build up, which might mean stronger effects and more of its usual side effects like headache, flushing, a stuffy nose, dizziness, or a drop in blood pressure.

The honest part: this is only seen in test tube research, not in actual people, so it's theoretical for now. Sildenafil is already active on its own (not a prodrug), so the concern is too much, not too little. Since kava can also stress the liver, it's worth a quick chat with your pharmacist or doctor before combining them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Mathews JM, Etheridge AS, Black SR. Inhibition of human cytochrome P450 activities by kava extract and kavalactones. Drug Metab Dispos 2002;30:1153-7. PubMed
  2. Unger M, Frank A. Simultaneous determination of the inhibitory potency of herbal extracts on the activity of six major cytochrome P450 enzymes using liquid chromatography/mass spectrometry and automated online extraction. Rapid Commun Mass Spectrom 2004;1 PubMed
Minor

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

2 of 2

Sildenafil also falls under 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.
Severity Minor Likelihood Unlikely Evidence B

Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the good news on combining kava with sildenafil (Viagra or Revatio): this pairing is rated as a very minor concern. Sildenafil is cleared from your body mostly by a liver enzyme called CYP3A4. Early lab-dish studies hinted that kava might slow that enzyme down, which in theory could let sildenafil build up and cause stronger effects like headache, flushing, a stuffy nose, or low blood pressure. But a better-quality human study found that kava had no real effect on CYP3A4 at all.

So in practice, this interaction is mostly theoretical. The bigger thing I'd mention is that kava can rarely stress the liver, so it's worth a quick chat with your pharmacist or doctor before using both, especially if you have any liver concerns.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Mathews JM, Etheridge AS, Black SR. Inhibition of human cytochrome P450 activities by kava extract and kavalactones. Drug Metab Dispos 2002;30:1153-7. PubMed
  2. Unger M, Frank A. Simultaneous determination of the inhibitory potency of herbal extracts on the activity of six major cytochrome P450 enzymes using liquid chromatography/mass spectrometry and automated online extraction. Rapid Commun Mass Spectrom 2004;1 PubMed
  3. 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. Clin Pharmacol Ther 2005;77:415-26. PubMed
  4. Asher GN, Corbett AH, Hawke RL. Common Herbal Dietary Supplement-Drug Interactions. Am Fam Physician. 2017;96(2):101-107.

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction 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.
  • PossibleInteraction 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.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Kava Also Interacts With Other Medications

Kava has 248 major, 576 moderate, 341 minor known drug interactions in our database — the Sildenafil one above is among them. If you take anything else, check it against the full list below.

Major 248 Moderate 576 Minor 341 No known interaction 1,665 (incl. Sildenafil)
Taking anything else?

Check Another of Your Medications Against Kava

Covers the 2,830 medications we’ve checked against Kava. Pick one to open its full report.

From our Q&A

Questions About Kava or Sildenafil

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Kava or Sildenafil, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Sildenafil

This page covers Kava only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Sildenafil page lists 160 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Mistletoe (major), Grapefruit (major), Hawthorn (major) and St. John's Wort (major).

By severity: 5 major · 114 moderate · 41 minor.

From our pharmacist’s overview on the Sildenafil page

“Sildenafil relaxes blood vessels, whether prescribed as Revatio for pulmonary hypertension or as Viagra, and that blood-pressure-lowering action makes this list one to treat with genuine care. Of the 160 supplement and herbal ingredients on file, five carry a major rating, and those deserve understanding first.”

Reviewed by 2 · Jul 18, 2026

Open the Sildenafil interaction page

One more smart check

Taking Kava as Part of a Dietary Supplement Product? Check It for Interactions

We hold 403 real supplement products containing Kava, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Kava. Your product may carry other ingredients that interact with Sildenafil too, on top of Kava — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Kava and Sildenafil Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Kava
Top 25%

#288 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Sildenafil
Top 25%

#434 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Kava

What is Kava?

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

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.

Read the full Kava monograph & all interactions
Medication

About Sildenafil

What Is Sildenafil Used For?

Brand name: Revatio

Sildenafil treats two distinct conditions depending on the product. Viagra (tablet) and Vybrique (dissolving oral film) are approved for erectile dysfunction (ED) — difficulty getting or keeping an erection. Generic sildenafil tablets and oral film are also approved for ED.

Revatio and several generic sildenafil products (tablets, oral suspension, and injection) are used for pulmonary arterial hypertension (PAH) — high blood pressure in the arteries of the lungs — in adults to improve exercise ability and slow the disease from getting worse. Revatio oral suspension and injection are also approved for PAH in children ages 1 to 17.

See full Sildenafil drug information
Keep checking

Other Drugs & Kava

Browse every other medication we’ve checked against Kava — both the ones with a known interaction and the ones without. Select any drug for the full detail.

248Major
576Moderate
341Minor
1,664No known interaction
248 Major 576 Moderate 341 Minor 1,664 No interaction
Major

248 interactions

Showing 60 of 248 major interactions — see all 248 on the Kava page.

Moderate

576 interactions

Showing 60 of 576 moderate interactions — see all 576 on the Kava page.

Minor

341 interactions

Showing 60 of 341 minor interactions — see all 341 on the Kava page.

No interaction 1,664 drugs checked — show the list

We also checked Kava against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 1,664 medications checked with no known interaction — see the full Kava list.

See the full Kava interactions page
See every supplement checked against Sildenafil, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Kava monograph › Uses, safety, and every drug interaction in one place Sildenafil supplement interactions › Every supplement checked against Sildenafil, ranked by severity Sildenafil drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Kava and Sildenafil Together: Common Questions

Can you take Kava with Sildenafil?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 2 interactions listed for Kava and Sildenafil?
Sildenafil belongs to more than one drug category, and Kava interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Kava and Sildenafil interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Sildenafil and Kava?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.