Drug & supplement interaction

Kava + Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine

Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine brand name: Vicks NyQuil.

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

Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine falls into 5 drug categories that Kava can interact with; the most serious is rated moderate. Theoretically, using kava with hepatotoxic drugs might increase the risk of liver damage.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions5
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Kava and Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine

These two interact in 5 distinct ways. Each one is explained separately below.

Why Are There 5 Interactions?

Kava interacts with whole categories of medication. Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine falls into 5 of those categories, so it can interact with Kava in 5 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

HEPATOTOXIC DRUGS

1 of 5

Why this applies to Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine

Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine falls under HEPATOTOXIC DRUGS — the group Kava interacts with.

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.
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

The piece of NyQuil to focus on here is the acetaminophen (the same active ingredient as Tylenol). Acetaminophen is processed by your liver, and in higher doses it's one of the more common causes of liver strain. Kava has been tied to rare but real cases of liver injury, mostly with heavy or long-term use. So the worry is simple: stacking two things that can each tax the liver may add up.

This concern is mostly theoretical and based on scattered case reports, not strong studies, so try not to panic. An occasional dose of NyQuil for a cold likely isn't a big deal, but regular kava plus regular acetaminophen is where I'd be careful. Watch for yellowing skin or eyes, dark urine, or belly pain, and check with your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Escher M, Desmeules J, Giostra E, Mentha G. Hepatitis associated with Kava, a herbal remedy for anxiety. BMJ 2001;322:139.
  2. Russmann S, Lauterburg BH, Helbling A. Kava hepatotoxicity [letter]. Ann Intern Med 2001;135:68-9.
  3. Liver Toxicity With Kava. Pharmacist's Letter/Prescriber's Letter. January 2001.
  4. Consultation letter MLX 286: Proposals to prohibit the herbal ingredient Kava-Kava (Piper methysticum) in unlicensed medicines. Medicines Control Agency, United Kingdom, July 19, 2002.
  5. Li XZ, Ramzan I. Role of ethanol in kava hepatotoxicity. Phytother Res 2010;24:475-80. PubMed
  6. Chanwai, L. G. Kava toxicity. Emergency Medicine 2002;12:142-145.
Moderate

CYTOCHROME P450 2E1 (CYP2E1) SUBSTRATES

2 of 5

Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine also falls under 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.
Severity Moderate Likelihood Probable Evidence B

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..

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

Here's something worth knowing if you reach for NyQuil while taking kava. One of the active ingredients, acetaminophen (Tylenol), is partly broken down by a liver enzyme called CYP2E1. A small study found that kava can slow that enzyme down. The catch is that CYP2E1 is the same pathway that turns a little bit of acetaminophen into a substance that can stress the liver. So kava slowing it isn't the main worry here.

The bigger picture is that both kava and acetaminophen have each been tied to liver problems on their own, so stacking them isn't ideal, especially with regular use. NyQuil also already contains a sedating antihistamine (doxylamine), and kava is calming too, so together you may feel extra drowsy or foggy. This is occasional-use advice, not a reason to panic. Please run it by your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. 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
Minor

CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES

3 of 5

Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine also falls under 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.
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

Let's talk about combining kava with NyQuil. On paper, the concern is that kava might slow down a liver enzyme called CYP1A2, which could let certain medicines build up. But the better-quality research here is reassuring: when healthy people took kava daily for nearly a month, it didn't actually change CYP1A2 activity. So this particular interaction is rated as minor and unlikely, and most of NyQuil's ingredients aren't even cleared mainly by that enzyme.

My bigger, more practical worry is overlap, not enzymes. Kava and NyQuil's doxylamine and dextromethorphan can each make you drowsy, so together you may feel extra sleepy or foggy. Also, both kava and the acetaminophen in NyQuil can stress the liver, so it's worth running this combination by your pharmacist first.

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. Toohey TP, Lu BY, Wada C. Toxic effects of psychotropics related to possible p450 enzyme inhibition by kava:report of 2 cases. Prim Care Companion CNS Disord 2013;15(5). PubMed
  5. Asher GN, Corbett AH, Hawke RL. Common Herbal Dietary Supplement-Drug Interactions. Am Fam Physician. 2017;96(2):101-107.
Minor

CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES

4 of 5

Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine also falls under 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.
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

If you're reaching for NyQuil while taking kava, here's the real story. In a test tube, kava looked like it might block CYP2D6, an enzyme that helps your body process the dextromethorphan (the cough suppressant) in NyQuil. In theory, slowing that enzyme could let dextromethorphan build up a bit, leading to more drowsiness or dizziness. But here's the reassuring part: actual studies in people showed kava did not meaningfully change how this enzyme works. So this interaction is rated minor and unlikely.

What I'd watch more closely is the overlap in sedation. Kava is calming, and NyQuil already contains doxylamine, which makes you sleepy, so together you may feel extra groggy. Check with your pharmacist 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
  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. Gurley BJ, Swain A, Hubbard MA, et al. Clinical assessement of CYP2D6-mediated herb-drug interactions in humans: Effects of milk-thistle, black cohosh, goldenseal, kava kava, St. John's wort, and Echinacea. Mol Nutr Food Res 2008;52:755-63.
  5. Asher GN, Corbett AH, Hawke RL. Common Herbal Dietary Supplement-Drug Interactions. Am Fam Physician. 2017;96(2):101-107.
Minor

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

5 of 5

Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine 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 the chemistry side: while early lab tests hinted that kava might slow down CYP3A4 (one of the liver enzymes that helps process the dextromethorphan in NyQuil), better human studies showed kava doesn't really affect that enzyme. So a meaningful jump in NyQuil's blood levels from this pathway is unlikely.

What I'd actually keep an eye on is overlap, not metabolism. Both kava and NyQuil's doxylamine (an antihistamine) and dextromethorphan can leave you drowsy, foggy, and uncoordinated, and the combo could pile that on. Kava has also been tied to rare liver injury, and NyQuil contains acetaminophen (Tylenol), which is hard on the liver too. Please run this past your pharmacist 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
  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 Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine 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. Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine)
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.

Everything else you take

See Every Supplement That Interacts With Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine

This page covers Kava only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine page lists 286 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Asarabacca (major), Beer (major), Ephedra (major) and Grapefruit (major).

By severity: 14 major · 227 moderate · 45 minor.

Open the Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine 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 Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine 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 Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine 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%

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

29 days ago today
Medication Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine
Top half

#973 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
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 Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine, 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 Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine supplement interactions › Every supplement checked against Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine, ranked by severity 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 Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine Together: Common Questions

Can you take Kava with Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine?
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 5 interactions listed for Kava and Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine?
Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine 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 Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine 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 Acetaminophen, Dextromethorphan, Doxylamine, Pseudoephedrine 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.