Methimazole

An antithyroid medicine, FDA-approved for hyperthyroidism from Graves' disease or toxic multinodular goiter and before thyroid surgery or radioiodine.

psilodex.org/m/methimazole · data v2026.10.05

Clinical contraindication: None listed; No label contraindication covering psilocybin was found. This is not a finding that the combination has been shown to be without risk.
Psilocybin evidence: No psilocybin data
Half-life: 4.9–5.7 h; Approximate, in adults. Source under Interaction below.

Named in state rules?

Not namedColorado

Not namedOregon

PendingNew Mexico

Cite asPsilodex, “Methimazole”, v2026.10.05. psilodex.org/m/methimazole

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

What it is used for

FDA status

FDA-approved

FDA-approved for

Hyperthyroidism from Graves' disease or toxic multinodular goiter (when surgery or radioactive iodine is not appropriate)
Hyperthyroid symptoms before thyroidectomy or radioactive iodine therapy

Sources [1]

Other safety

The label warns of agranulocytosis (fever or sore throat as early signs), liver toxicity, vasculitis and birth defects with first-trimester use.

About the medication itself, separate from any interaction with psilocybin.

Sources [1]

01 Interaction with psilocybin

Not studied with psilocybin, and no mechanism linking them has been described. Also, untreated overactive thyroid raises heart rate and blood pressure.

Detail Methimazole has not been studied with psilocybin and has no known pharmacologic interaction. Untreated or undertreated hyperthyroidism (overactive thyroid) raises heart rate and blood pressure, as psilocybin does briefly. Separately, its label warns of agranulocytosis (very low white blood cells) and liver toxicity.

Human data with psilocybin: No psilocybin data; based on its label
Half-life: 4.9–5.7 h (article, checked 2026-10-04)

Evidence types on this record

No psilocybin dataNo psilocybin data: no human data with psilocybin or another classic psychedelic; the text draws on the medication's own pharmacology and its label or reference facts

02 Pharmacology relevant to psilocybin

1 listed · counted on reports

Liver injury: The label or source warns of liver injury, from raised liver enzymes to liver failure. Liver disease also affects how the body clears psilocin. Sources [1]

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 2026-10-04

OROAR 333-333

Not named

No provision names this medication or its class.

Oregon · checked 2026-10-04

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 2026-10-04

04 Conditions to ask about

None linked

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

05 Sources

METHIMAZOLE tablets (Chartwell) · FDA label (DailyMed) — Liver injury: Warnings, Liver Toxicity "Although there have been reports of hepatotoxicity (including acute liver failure) associated with methimazole, the risk of hepatotoxicity appears to be less with methimazole than with propylthiouracil"
Jansson R, Lindström B, Dahlberg PA. Pharmacokinetic properties and bioavailability of methimazole. Clin Pharmacokinet 1985;10(5):443–450. — Abstract: "Following intravenous administration of 10mg to healthy subjects, methimazole had an initial distribution half-life (t1/2 alpha) of 0.10 to 0.23 hours and an elimination half-life (t1/2 beta) of 4.9 to 5.7 hours."

Record history

v2026.10.02First published.
2026-10-04Last reviewed against its sources.

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