Drug & supplement interaction

Kava + Codeine Phosphate

Codeine Phosphate brand name: Codeine.

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

Codeine Phosphate falls into 2 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
Interactions2
EvidenceA
What do Severity, Likelihood & Evidence mean?
Know someone taking this? Share
Facebook Post Reddit Email
On this page
Interaction report

Kava and Codeine Phosphate

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. Codeine Phosphate 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 (Major).

Major

CNS DEPRESSANTS

1 of 2

Why this applies to Codeine Phosphate

Codeine Phosphate 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 watch with this combo: both kava and codeine can calm down your central nervous system. Codeine is an opioid that already causes drowsiness and slows your breathing a bit, and kava has its own sedating effect. Put them together and those effects can stack up. That means more sleepiness, slower reflexes, dizziness, and in a worst-case situation, breathing that gets too slow or shallow.

This isn't a far-fetched worry. Expert guidelines actually advise against pairing kava with sedating medicines. There's also kava's separate risk of liver harm to keep in mind. Please don't start or stop anything on your own. Check with your pharmacist or doctor first, especially before driving or doing anything that needs you alert.

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
Minor

CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES

2 of 2

Codeine Phosphate 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 something worth knowing about codeine: it's actually a prodrug. Your body has to convert it into morphine using a liver enzyme called CYP2D6 before it can ease your pain or quiet a cough. So anything that blocks that enzyme could, in theory, leave you with weaker pain relief.

Now, lab studies suggested kava might slow CYP2D6, which would mean less codeine gets turned into its active form. But here's the reassuring part: actual studies in people showed kava did not meaningfully change how this enzyme works. So the real-world risk looks low. Concentrated kava supplements are stronger than an occasional traditional drink. Since both can be sedating and kava can stress the liver, please check 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
  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 Codeine Phosphate 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. Codeine Phosphate)
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 Codeine Phosphate

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 Codeine Phosphate, 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 Codeine Phosphate

This page covers Kava only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Codeine Phosphate page lists 144 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).

By severity: 7 major · 114 moderate · 23 minor.

From our pharmacist’s overview on the Codeine Phosphate page

“Codeine phosphate is an opioid painkiller and cough suppressant that slows breathing along with brain activity, and the wrong supplement can push that effect into dangerous territory. Seven of the 144 documented ingredients rate major, and nearly all of that serious risk comes from things that deepen sedation.”

Reviewed by 2 · Jul 18, 2026

Open the Codeine Phosphate 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 Codeine Phosphate 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 Codeine Phosphate 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%

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

29 days ago today
Medication Codeine Phosphate
Top half

#756 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 Codeine

What Is Codeine Used For?

Brand name: Codeine

Codeine Sulfate tablets are used to manage mild to moderate pain in adults when non-opioid pain treatments have not worked or are not tolerated. It is only appropriate when an opioid is truly needed.

Because of the serious risks of addiction, misuse, overdose, and death, codeine is reserved for patients whose pain cannot be managed adequately with other options. It is not a first-choice pain reliever.

See full Codeine 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.

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 Codeine Phosphate, 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 Codeine Phosphate supplement interactions › Every supplement checked against Codeine Phosphate, ranked by severity Codeine 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 Codeine Phosphate Together: Common Questions

Can you take Kava with Codeine Phosphate?
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 2 interactions listed for Kava and Codeine Phosphate?
Codeine Phosphate 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 Codeine Phosphate 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

Still Have a Question About Codeine Phosphate and Kava?

Our pharmacists answer your medication & supplement questions — free.

Ask a pharmacist

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.