The short answer
Check with your prescriber before combining kava with isocarboxazid. Extra drowsiness or impairment is a reasonable concern, but direct studies have not established the size or frequency of this interaction.
What this answer covers
Piper methysticum beverages and extracts; preparations vary. Taken orally with oral isocarboxazid tablets; other species and preparations are not interchangeable.
- Supplement or preparation
- Piper methysticum
- Medication ingredient
- isocarboxazid
Why caution is reasonable
Marplan can cause drowsiness and faintness and warns against some central nervous system depressants. NCCIH advises against mixing kava with sedating substances.
What the studies do not establish
A four-week randomized trial found neither kava nor valerian more effective than placebo for the primary anxiety or insomnia outcomes. It did not test coadministration with isocarboxazid. A lack of benefit does not demonstrate that the combination is safe.
Review the product before starting
Give your prescriber or pharmacist the exact extract, dose and all other sleep or anxiety products you take. Avoid adding alcohol or other sedating products. Do not stop prescribed Marplan or use dose separation as an assumed solution.
Practical safety
If you become drowsy, dizzy or mentally slowed, do not drive or operate machinery and contact your clinician. Kava also carries a separate rare liver-injury concern; this is not proof that isocarboxazid increases that risk.
Evidence and practical considerations
Side effects & toxicity
Check with your prescriber before combining kava with isocarboxazid. Extra drowsiness or impairment is a reasonable concern, but direct studies have not established the size or frequency of this interaction.
- Exact scope
- Piper methysticum beverages and extracts; preparations vary. Taken orally with oral isocarboxazid tablets; other species and preparations are not interchangeable. with isocarboxazid, RxCUI 6011 IN; oral MARPLAN tablets.
- Medication form and route
- Oral isocarboxazid; oral supplement
What remains uncertain
- The exact-pair sedation claim remains unconfirmed. Marplan drowsiness and CNS-depressant warnings plus botanical precautions justify cautious management, not a quantified or proven combination effect.
Factors that may matter: Exact product composition and dose; Other medicines and supplements.
Read the supporting source summaries
Source 1: Current U.S. prescribing information
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: Patients prescribed oral isocarboxazid tablets.
Phenylalanine is named among substances that may precipitate hypertension and headache. Sympathomimetics, some CNS depressants and excessive caffeine are contraindicated. The label describes high-tyramine hypertensive crises and warns about drowsiness, hypotension and impaired driving.
How this applies: Exact isocarboxazid authority. Botanical applicability must be assessed from the relevant constituent or sedating effect rather than a botanical name alone.
The label does not quantify these botanical pair risks or give a universally safe supplement dose.
Source 2: Federal botanical safety information
nccih.nih.gov · Source check Sep 10, 2026
Population: Users of Kava preparations; not an exact-pair trial.
Advises against combining kava with substances that have sedative effects. Describes dizziness and rare serious liver injury.
How this applies: A general precaution, not a measured isocarboxazid interaction. Liver injury is an intrinsic kava concern, not proof of additive pair hepatotoxicity.
A general precaution, not a measured isocarboxazid interaction. Liver injury is an intrinsic kava concern, not proof of additive pair hepatotoxicity.
Source 3: Original randomized human study
ebi.ac.uk · Source check Sep 10, 2026
Population: 391 participants with anxiety and insomnia.
Neither herbal treatment improved its primary anxiety or insomnia outcome more than placebo.
How this applies: Abstract only; no isocarboxazid comparison and no quantified interaction outcome. Lack of efficacy does not prove lack of sedation or establish safety with an MAOI.
Abstract only; no isocarboxazid comparison and no quantified interaction outcome. Lack of efficacy does not prove lack of sedation or establish safety with an MAOI.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Sources checked and article drafted. | |
| Research summary published |
Article revision: 12171bb7578780ff
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.