Promethazine

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

Named in state rules?

COUnsettled

ORNot named

NMPending

Cite asPsilodex: promethazine · v2026.10.02

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

01 Interaction with psilocybin

Phenothiazine D2 and H1 blocker; anticholinergic and sedating.

Human data with psilocybin: None known: no published human data with psilocybin

Evidence types on this record

ThMechanism only (theoretical)

02 Pharmacology relevant to psilocybin

2 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]
Sedating or CNS depressant: Slows the central nervous system: drowsiness, slower reactions and impaired coordination, and slowed breathing at high doses. Effects add with other sedating substances. Sources [1]

03 State rules

Official text governs

CO4 CCR 755-1

Unsettled · 2.2(A)(6)–(7)

Whether this drug counts as an “antipsychotic” under the rule is unsettled: it is a phenothiazine or has antipsychotic-like activity but is usually prescribed for another purpose. Programs differ on whether the antipsychotic provision applies.

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

Phenergan (Promethazine Hcl) Tablet · FDA label (DailyMed)

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