The short answer
Kava may add to codeine-related drowsiness or impairment. The exact added risk is unmeasured, so review the product before combining it with the prescription.
What this answer covers
Piper methysticum beverages and extracts; not isolated kavalactones or every product.
- Supplement or preparation
- Piper methysticum
- Medication ingredient
- codeine
The supplement can affect alertness
Supplement guidance advises against combining kava with sedating substances. The tested kava/valerian trial’s lack of anxiety or sleep benefit does not exclude sedation.
Codeine’s opioid effects can be serious
The codeine label warns of profound sedation and impaired breathing with CNS depressants. Conversion to morphine and other medicines influence the response, so the same dose does not affect everyone equally.
Product identity and dose matter
A different preparation or release form may behave differently. No safe supplement dose or short separation interval has been established for this combination.
Discuss co-use and respond to impairment
Ask the prescriber before adding it and avoid driving while impaired. Slow or difficult breathing or unusual difficulty waking requires emergency help. Do not change the codeine dose yourself.
Evidence and practical considerations
Side effects & toxicity
Conditional additive-drowsiness precaution from exact codeine label and supplement-specific guidance/effects; no pair incidence or demonstrated respiratory-depression magnitude. Preparation/species limits retained.
- Exact scope
- Piper methysticum beverages and extracts; not isolated kavalactones or every product. with Codeine RxCUI2670 IN; current oral single-ingredient sulfate label, active morphine metabolism and formulation boundaries.
- Medication form and route
- oral medication; oral supplement
What remains uncertain
- No unmeasured pair incidence, blanket class transfer or arbitrary spacing interval.
Factors that may matter: Preparation; Dose; Other medicines; Organ function.
Read the supporting source summaries
Source 1: current product label
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: People prescribed codeine
Codeine is converted to active morphine via CYP2D6. CYP2D6 inhibition can reduce morphine/effect despite increased codeine; CYP3A interactions complicate disposition. CNS-depressant combinations can cause serious sedation/respiratory depression.
How this applies: Exact codeine RxCUI 2670 IN, with stated salt/formulation/route bridge.
Not cough combination products or every salt formulation. No exact botanical risk rate; genotype, age and co-medications matter.
Source 2: federal supplement safety guidance
nccih.nih.gov · Source check Sep 10, 2026
Population: Users of the specified supplement.
Kava should not be used with other sedating substances. Various kava products have been linked to rare liver injury, sometimes serious or fatal.
How this applies: Original source interpreted for codeine only within the stated preparation and endpoint limits.
Not a direct codeine combination trial; original preparation, dose and endpoint limits apply. No exact-pair adverse-event rate or protective spacing established.
Source 3: original human study
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: 391 participants with anxiety and insomnia.
Neither botanical improved its primary anxiety/insomnia outcome over placebo.
How this applies: Original source interpreted for codeine only within the stated preparation and endpoint limits.
Not a direct codeine combination trial; original preparation, dose and endpoint limits apply. No exact-pair adverse-event rate or protective spacing established.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Prepared exact codeine article with formulation-specific evidence and uncertainty. | |
| Research summary published |
Article revision: 918211591e65f7cc
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
Taking other supplements or medications?
Use the checker to explore your other combinations. Ask a pharmacist to review the exact products, amounts and medical conditions in your complete list.
Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.