The short answer
Kava may add to dextromethorphan-related drowsiness or impairment. Review the exact products before co-use; a universal avoidance rule or protective timing gap has not been established.
What this answer covers
Piper methysticum beverages and extracts; strength and co-ingredients vary.
- Supplement or preparation
- Piper methysticum
- Medication ingredient
- dextromethorphan
Drowsiness is possible
Dextromethorphan can cause dizziness or drowsiness. Official supplement guidance cautions about combining this herb with sedating substances.
What the evidence does not establish
A reported serotonin-syndrome case included kava, a dextromethorphan-containing cough product and several psychiatric medicines. It cannot isolate this pair or prove additive sedation.
Read every active ingredient
Single-ingredient dextromethorphan caplets and extended-release suspension have different schedules. A multi-symptom cough product can contain additional sedating ingredients; its effects should not be attributed solely to dextromethorphan.
A short gap is not established protection
Review co-use with a pharmacist and avoid driving while drowsy. No trial defines a protective spacing interval or universal need to avoid the pair. Excess dosing, trouble breathing or inability to wake calls for immediate medical help.
Evidence and practical considerations
Side effects & toxicity
Conditional additive-drowsiness precaution from exact medication side-effect guidance and supplement effects; no transferable pain-opioid respiratory-depression rates or exact pair magnitude.
- Exact scope
- Piper methysticum beverages and extracts; strength and co-ingredients vary. with Dextromethorphan3289 IN; oral cough hydrobromide/polistirex formulations, not codeine or other pain opioids; psychiatric combinations explicitly limited.
- 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 dextromethorphan
Cough suppressant with age-specific directions, overdose precautions and prohibition during prescription MAOI use or within2weeks after stopping that drug.
How this applies: Exact dextromethorphan RxCUI 3289 IN, with stated salt/formulation/route bridge.
Not a pain opioid label, not a sedating antihistamine combination, and MAOI interval cannot be assigned to every herb.
Source 2: current product label
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: People prescribed dextromethorphan
Different age-specific schedule and release duration from caplets; MAOI prohibition and overdose precautions.
How this applies: Exact dextromethorphan RxCUI 3289 IN, with stated salt/formulation/route bridge.
Not interchangeable dosing with immediate-release products or psychiatric combinations containing a CYP2D6 inhibitor.
Source 3: national medication patient information
medlineplus.gov · Source check Sep 10, 2026
Population: People using dextromethorphan cough medicines
Possible dizziness and drowsiness; disclose supplements and other medicines; overdose can cause serious neurologic and breathing problems.
How this applies: Exact medication effects and review advice.
No exact supplement interaction incidence; overdose outcomes are not routine therapeutic-dose event rates.
Source 4: 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 dextromethorphan only within the stated preparation and endpoint limits.
Not a direct dextromethorphan combination trial; original preparation, dose and endpoint limits apply. No exact-pair adverse-event rate or protective spacing established.
Source 5: 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 dextromethorphan only within the stated preparation and endpoint limits.
Not a direct dextromethorphan combination trial; original preparation, dose and endpoint limits apply. No exact-pair adverse-event rate or protective spacing established.
Source 6: original confounded multi-product case report
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: One16-year-old patient.
Prolonged serotonin-syndrome features; authors emphasized kava and antidepressant interaction.
How this applies: Multiple serotonergic and sedating agents; cannot isolate dextromethorphan-kava causation, quantify risk or use a serotonin endpoint to prove additive sedation.
Multiple serotonergic and sedating agents; cannot isolate dextromethorphan-kava causation, quantify risk or use a serotonin endpoint to prove additive sedation.
Research assessment: · Open full citations ↗
Timing & monitoring
No evidence establishes a required separation interval or universal avoidance. Product review and alertness precautions are justified, but they do not prove the current timing/avoidance claim.
- Exact scope
- Piper methysticum beverages and extracts; strength and co-ingredients vary. with Dextromethorphan3289 IN; oral cough hydrobromide/polistirex formulations, not codeine or other pain opioids; psychiatric combinations explicitly limited.
- 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 dextromethorphan
Cough suppressant with age-specific directions, overdose precautions and prohibition during prescription MAOI use or within2weeks after stopping that drug.
How this applies: Exact dextromethorphan RxCUI 3289 IN, with stated salt/formulation/route bridge.
Not a pain opioid label, not a sedating antihistamine combination, and MAOI interval cannot be assigned to every herb.
Source 2: current product label
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: People prescribed dextromethorphan
Different age-specific schedule and release duration from caplets; MAOI prohibition and overdose precautions.
How this applies: Exact dextromethorphan RxCUI 3289 IN, with stated salt/formulation/route bridge.
Not interchangeable dosing with immediate-release products or psychiatric combinations containing a CYP2D6 inhibitor.
Source 3: national medication patient information
medlineplus.gov · Source check Sep 10, 2026
Population: People using dextromethorphan cough medicines
Possible dizziness and drowsiness; disclose supplements and other medicines; overdose can cause serious neurologic and breathing problems.
How this applies: Exact medication effects and review advice.
No exact supplement interaction incidence; overdose outcomes are not routine therapeutic-dose event rates.
Source 4: 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 dextromethorphan only within the stated preparation and endpoint limits.
Not a direct dextromethorphan combination trial; original preparation, dose and endpoint limits apply. No exact-pair adverse-event rate or protective spacing established.
Source 5: 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 dextromethorphan only within the stated preparation and endpoint limits.
Not a direct dextromethorphan combination trial; original preparation, dose and endpoint limits apply. No exact-pair adverse-event rate or protective spacing established.
Source 6: original confounded multi-product case report
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: One16-year-old patient.
Prolonged serotonin-syndrome features; authors emphasized kava and antidepressant interaction.
How this applies: Multiple serotonergic and sedating agents; cannot isolate dextromethorphan-kava causation, quantify risk or use a serotonin endpoint to prove additive sedation.
Multiple serotonergic and sedating agents; cannot isolate dextromethorphan-kava causation, quantify risk or use a serotonin endpoint to prove additive sedation.
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 dextromethorphan article with formulation-specific evidence and uncertainty. | |
| Research summary published |
Article revision: f5f6125d41de52ac
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.