Chlorpromazine

Clinical contraindication: Relative; Substantial clinical concern; the literature treats it as a reason for caution or deferral.
Best available evidence: Controlled trial
Half-life: Not recorded

Named in state rules?

CONamed

ORNot named

NMPending

Cite asPsilodex: chlorpromazine · v2026.10.02

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

01 Interaction with psilocybin

RCT

Pretreatment with 50 mg chlorpromazine 2 h before psilocybin reduced pupil dilation and visual distortion (Keeler 1967). Lowers seizure threshold; hypotension; anticholinergic.

Human data with psilocybin: Human studies with psilocybin

Evidence types on this record

RCTControlled trial

02 Pharmacology relevant to psilocybin

4 listed · counted on reports

Anticholinergic: Blocks acetylcholine. Can cause a fast heart rate, dry mouth, reduced sweating and heat intolerance, and confusion, more so at high doses or in combination. Sources [1]
Blocks 5-HT2A (may blunt effects): Blocks the 5-HT2A receptor, the main receptor psilocybin acts through. Can reduce or block the psilocybin effect. Sources [2]
Lowers blood pressure or causes orthostasis: Lowers blood pressure, or causes a drop on standing (orthostasis) that can bring dizziness or fainting. Sources [1]
Lowers seizure threshold or carries seizure risk: Makes a seizure more likely, or has been linked to seizures. Sources [1]

03 State rules

Plain-language summary · official text governs

CO4 CCR 755-1

Named · 2.2(A)(6)–(7) · 2.5(A)(2)

Antipsychotic medications are named in rule, regardless of indication or dose. A Facilitator licensee may not provide services to a participant taking one without a referral for natural medicine services from a licensed provider, medical clearance from their medical or behavioral health provider, or a consultation and risk review with a medical or behavioral health provider. A Clinical Facilitator who does not prescribe antipsychotics within their secondary license needs clearance from, or a consultation and risk review with, such a provider.

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

Screening items in state rules

This medication is usually taken for a condition. State rules screen for some conditions directly, so the medication is a prompt to ask about them. Confirm with the participant; never assume a condition from the medication.

Psychotic disorder or bipolar disorder (common indications)CO 2.2(A)(6)–(7) · CO 2.5(A)(2) · OR 333-333-5050(3)(j)

05 Sources

chlorproMAZINE Hydrochloride Tablets, USP Rx only · FDA label (DailyMed)
Brunton LL, Knollmann BC (eds). Goodman & Gilman’s The Pharmacological Basis of Therapeutics, 14th ed. McGraw Hill, 2023., p. 1127
Keeler MH. Chlorpromazine antagonism of psilocybin effect. Int J Neuropsychiatry 1967;3:66–71.
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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