Isocarboxazid

Clinical contraindication: Absolute; The clinical literature treats the combination as contraindicated.
Best available evidence: Other psychedelic; Human data with another classic psychedelic (e.g. LSD), not psilocybin; named in the text.
Half-life: Not recorded

Named in state rules?

CONot named

ORNot named

NMPending

Cite asPsilodex: isocarboxazid · v2026.10.02

Clinical data and state rules are separate facts. Both are shown; neither is a decision.

01 Interaction with psilocybin

With LSD, isocarboxazid pretreatment reduced psychological and autonomic effects (Resnick 1964). No psilocybin data. MAO inhibition can raise blood pressure with psilocybin (see tranylcypromine); serotonin toxicity is theoretical, with no reported human case.

Human data with psilocybin: None with psilocybin; human data with another psychedelic
Common practice: Where discontinuation is considered, product labeling describes a washout of at least two weeks before starting a serotonergic drug. Any change is prescriber-managed.

Evidence types on this record

XPHuman data with another classic psychedelic (e.g. LSD), not psilocybin; named in the text

02 Pharmacology relevant to psilocybin

3 listed · counted on reports

MAO inhibition: Inhibits monoamine oxidase, the enzyme that breaks down serotonin and other monoamines. MAO also helps clear psilocin, so it can change how strong and how long the psilocybin effect is, and it raises serotonin levels. Sources [1]
Raises blood pressure or heart rate: Raises blood pressure or heart rate. Psilocybin raises both for several hours, so the effects can add. Sources [1]
Serotonergic: Increases serotonin activity, for example by blocking its reuptake or releasing it. Psilocybin acts on serotonin receptors, so effects can add together. With antidepressant use, the psilocybin response can be weaker. Sources [2]

03 State rules

Plain-language summary · official text governs

CO4 CCR 755-1

Not named

No provision names this medication or its class.

Colorado · checked 2026-09-30

OROAR 333-333

Not named

No provision names this medication or its class.

Oregon · checked 2026-09-30

NM7.35.3 NMAC (proposed)

Pending

New Mexico's clinical rules (proposed 7.35.3 NMAC) are not final. No provision naming this medication has been found.

New Mexico · checked 2026-09-30

04 Conditions to ask about

None linked

No condition named in state rules is linked to this medication.

05 Sources

Marplan · FDA label (DailyMed)
Preston CL (ed). Stockley’s Drug Interactions, 11th ed. Pharmaceutical Press, 2016., p. 1407
Resnick O, Krus DM, Raskin M. LSD-25 action in normal subjects treated with a monoamine oxidase inhibitor. Life Sci 1964;3:1207–1214.
Halman A, Kong G, Sarris J, Perkins D. Drug–drug interactions involving classic psychedelics: a systematic review. J Psychopharmacol 2024;38(1):3–18.

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