Drug & supplement interaction

Kava + Propoxyphene Napsylate

Propoxyphene Napsylate brand name: Darvon N.

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

Propoxyphene Napsylate falls into 3 drug categories that Kava can interact with; the most serious is rated major. Combining kava with CNS depressants can have additive sedative effects.

Read the full interaction report
SeverityMajor
LikelihoodProbable
Interactions3
EvidenceA
What do Severity, Likelihood & Evidence mean?
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Interaction report

Kava and Propoxyphene Napsylate

These two interact in 3 distinct ways. Each one is explained separately below.

Why Are There 3 Interactions?

Kava interacts with whole categories of medication. Propoxyphene Napsylate falls into 3 of those categories, so it can interact with Kava in 3 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Major).

Major

CNS DEPRESSANTS

1 of 3

Why this applies to Propoxyphene Napsylate

Propoxyphene Napsylate falls under CNS DEPRESSANTS — the group Kava interacts with.

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.
Severity Major Likelihood Probable Evidence A

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 the thing to know about pairing kava with propoxyphene napsylate (Darvon N). Propoxyphene is an opioid pain reliever, and like all opioids it already slows down your central nervous system. Kava has its own calming, sedative-like effects on the brain. Stack the two together and those effects add up, so you may feel unusually drowsy, foggy, dizzy, or slow to react. In a worst-case scenario, the combination can deepen the breathing-slowing effect that opioids are known for, which is the real safety concern here.

This isn't a guess. Expert guidelines specifically warn against mixing kava with CNS depressants. One more note: both propoxyphene and kava can stress the liver, so that's another reason to be cautious. Please don't change anything on your own. Talk with your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Pittler MH, Ernst E. Efficacy of kava extract for treating anxiety: systematic review and meta-analysis. J Clin Psychopharmacol 2000;20:84-9. PubMed
  2. 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;27:46-53.
  3. Cairney S, Maruff P, Clough AR, et al. Saccade and cognitive impairment associated with kava intoxication. Hum Psychopharmacol 2003;18:525-33. PubMed
  4. Sarris J, Kavanagh DJ, Byrne G, et al. The Kava Anxiety Depression Spectrum Study (KADSS): a randomized, placebo-controlled crossover trial using an aqueous extract of Piper methysticum. Psychopharmacology 2009;205:399-407. PubMed
  5. Sarris J, Ravindran A, Yatham LN, et al. Clinician guidelines for the treatment of psychiatric disorders with nutraceuticals and phytoceuticals: The World Federation of Societies of Biological Psychiatry (WFSBP) and Canadian Network for Mood and Anxiety T
Moderate

HEPATOTOXIC DRUGS

2 of 3

Propoxyphene Napsylate also falls under 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.
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 thing to keep an eye on with this combination: it's really about your liver, not about kava changing how your pain medicine works. Kava has been tied to rare but serious liver injury, mostly with heavy or long-term use. Propoxyphene (Darvon N) is also one of those medicines that can be hard on the liver in some people, so stacking the two together may add to that stress.

I'll be honest, this concern is based mostly on case reports and theory, so it isn't a high-certainty interaction. Still, I'd watch for warning signs like yellowing of the skin or eyes, dark urine, belly pain, nausea, or unusual tiredness. Before mixing these, please check in 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.
Minor

CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES

3 of 3

Propoxyphene Napsylate 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

Here's the short version: on paper, kava can slow down a liver enzyme called CYP2D6, which is one of the pathways your body uses to process propoxyphene (Darvon N). If that pathway were blocked, you might worry about the medicine lingering longer and causing more of its usual effects, like extra drowsiness, dizziness, or slowed breathing.

But the real-world evidence is reassuring here. While lab dish studies showed kava blocking this enzyme, studies in actual people found kava did not meaningfully change how CYP2D6 medicines are handled. So this interaction is rated minor and unlikely. That said, both kava and propoxyphene can add to sedation and both stress the liver, so I'd still run this combo by your pharmacist or doctor before mixing 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.

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 247 major, 577 moderate, 341 minor known drug interactions in our database — the Propoxyphene Napsylate one above is among them. If you take anything else, check it against the full list below.

Major 247 Moderate 577 Minor 341 No known interaction 1,665 (incl. Propoxyphene Napsylate)
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 Propoxyphene Napsylate

This page covers Kava only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Propoxyphene Napsylate page lists 172 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: 1,4-butanediol (major), Activated Charcoal (major), Beer (major), Gamma-hydroxybutyrate (ghb) (major) and L-tryptophan (major).

Open the Propoxyphene Napsylate 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 Propoxyphene Napsylate 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 Propoxyphene Napsylate 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%

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

29 days ago today
Medication Propoxyphene Napsylate
Steady interest

#2,353 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.

247Major
577Moderate
341Minor
1,664No known interaction
247 Major 577 Moderate 341 Minor 1,664 No interaction
Major

247 interactions

Showing 60 of 247 major interactions — see all 247 on the Kava page.

Moderate

577 interactions

Showing 60 of 577 moderate interactions — see all 577 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 Propoxyphene Napsylate, 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 Propoxyphene Napsylate supplement interactions › Every supplement checked against Propoxyphene Napsylate, 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 Propoxyphene Napsylate Together: Common Questions

Can you take Kava with Propoxyphene Napsylate?
This is rated a major interaction, so the combination is best avoided unless your doctor or pharmacist has specifically told you otherwise. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 3 interactions listed for Kava and Propoxyphene Napsylate?
Propoxyphene Napsylate 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 Propoxyphene Napsylate interaction?
We rate it Major. This is a clinically significant combination that is generally best avoided, or used only under the direct supervision of your physician or pharmacist.

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

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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.