Methimazole

Category: pharmacological

Aliases: Tapazole

Pharmacological Mechanism

Thionamide antithyroid — inhibits thyroid peroxidase (TPO) blocking iodination of thyroglobulin tyrosines → halts thyroid hormone synthesis. First-line for Graves disease + thyroid storm (after PTU in early pregnancy). Agranulocytosis is the feared adverse effect.

Half-Life (t½)

PO: 5h

Dosing Guidelines

• PO: Typical 15 mg (Range: 5–40 mg)

Target Organ Systems

• endocrine

Pathways It Modulates

• Hypothalamic-pituitary-thyroid axis (inhibitor) — thyroid peroxidase (organification step)

Chemical Identifiers

• PubChem CID: 1349907
• Formula: C4H6N2S
• Molecular weight: 114.17 g/mol
• InChIKey: PMRYVIKBURPHAH-UHFFFAOYSA-N
• SMILES: CN1C=CNC1=S

References

• PMID 4042519
• PMID 6172233