The short answer
Discuss the exact cannabis product with your prescriber before using it with isocarboxazid. THC-containing products can impair performance, while Marplan can cause drowsiness. A direct interaction causing extra sedation has not been established for all Cannabis sativa products.
What this answer covers
Cannabis sativa is a broad identity covering very different products. The inspected human trial used vaporized cannabinoid-containing cannabis, not oral hemp seed, hemp oil, CBD supplements or topical products.
- Supplement or preparation
- Cannabis sativa
- Medication ingredient
- isocarboxazid
Why the exact product matters
A cannabis product may contain THC, CBD, both or very little of either. The human study reviewed here used vaporized cannabis with specified cannabinoid doses. Those results cannot be transferred directly to an oral hemp seed product or a topical preparation.
What was actually measured
In a small trial, THC-containing cannabis increased lane weaving soon after use. CBD-dominant cannabis did not show a significant difference from placebo, but meaningful impairment could not be excluded. Nobody in the reported comparison was receiving isocarboxazid.
How Marplan changes the discussion
Marplan itself can cause drowsiness and faintness and warns against some CNS depressants. These facts justify checking the combination with your prescriber, but do not establish a specific additive sedation rate or prove safety for CBD-only products.
Before using cannabis
Bring the product label, route, cannabinoid amounts and planned dose to your clinician. Do not drive when impaired. The study timing does not provide a safe waiting period with Marplan, and spacing the products by a few hours has not been validated.
Evidence and practical considerations
Side effects & toxicity
Discuss the exact cannabis product with your prescriber before using it with isocarboxazid. THC-containing products can impair performance, while Marplan can cause drowsiness. A direct interaction causing extra sedation has not been established for all Cannabis sativa products.
- Exact scope
- Cannabis sativa is a broad identity covering very different products. The inspected human trial used vaporized cannabinoid-containing cannabis, not oral hemp seed, hemp oil, CBD supplements or topical products. with isocarboxazid, RxCUI 6011 IN; oral MARPLAN tablets.
- Medication form and route
- Oral isocarboxazid; vaporized cannabis only in the standalone trial; oral supplement interaction unresolved
What remains uncertain
- Do not treat a broad botanical identity as proof of additive CNS depression. A vaporized THC trial establishes standalone driving impairment, not an oral supplement interaction with isocarboxazid. Precaution is reasonable; the original claim remains unconfirmed.
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: Original randomized human study
ebi.ac.uk · Source check Sep 10, 2026
Population: 26 healthy occasional cannabis users; 22 completed all driving tests.
THC-containing preparations increased lane weaving at 40 to 100 minutes. No significant CBD-dominant difference was detected, but clinically important impairment could not be excluded.
How this applies: Abstract only. No isocarboxazid; vaporized products and driving performance do not establish oral hemp supplement sedation, CNS depression, or a safe waiting period.
Abstract only. No isocarboxazid; vaporized products and driving performance do not establish oral hemp supplement sedation, CNS depression, or a safe waiting period.
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: bde3786c11de6fb0
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.