Dextromethorphan–quinidine

Clinical contraindication: None listed; No clinical contraindication identified.
Best available evidence: Mechanism only
Half-life: ~13 h; Approximate, in adults. Detail in 01.

Named in state rules?

CONot named

ORNot named

NMPending

Cite asPsilodex: dextromethorphan-quinidine · v2026.10.02

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

01 Interaction with psilocybin

Serotonergic DXM; quinidine QTc prolongation.

Human data with psilocybin: None known: no published human data with psilocybin
Half-life: DXM ~13 h; quinidine ~7 h (FDA label, checked 2026-09-30)

Evidence types on this record

ThMechanism only (theoretical)

02 Pharmacology relevant to psilocybin

2 listed · counted on reports

QT-prolonging: Lengthens the QT interval on an ECG, a measure of the heart’s electrical recovery between beats. A long QT raises the risk of a dangerous heart rhythm, more so with other QT-prolonging drugs or low potassium or magnesium. 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 [1]

03 State rules

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

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.

Neurologic disease (pseudobulbar affect)CO 2.5(A)(2)

05 Sources

Dextromethorphan–quinidine — prescribing information · FDA label (DailyMed)

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