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SYSTEMIC HORMONAL PREPARATIONS, EXCL. SEX HORMONES AND INSULINS › THYROID THERAPY › ANTITHYROID PREPARATIONS › Sulfur-containing imidazole derivatives
thiamazole
H03BB02
Forms & Strengths
- Oral tablets: 5 mg
- Oral tablets: 10 mg
- Oral tablets: 20 mg
Adult Dosing
- Hyperthyroidism: Initial 15 to 60 mg daily divided q8h, depending on severity
- Maintenance: 5 to 15 mg daily
- Thyroid storm: 40 mg q6h combined with other therapies
Pediatric Dosing
- Hyperthyroidism (Children > 3 years): Initial 0.4 mg/kg/day divided q8h
- Maintenance: Approximately 0.2 mg/kg/day divided q8h
Indications
- Hyperthyroidism (Graves' disease)
- Preparation for thyroidectomy or radioactive iodine therapy
- Thyroid storm
Mechanism of Action
- Inhibits the enzyme thyroid peroxidase
- Prevents oxidation of iodide and iodination of tyrosine residues in thyroglobulin
- Blocks synthesis of thyroid hormones (T3 and T4)
Contraindications
- Hypersensitivity to thiamazole or thioamide derivatives
- Lactation (due to excretion in breast milk)
- Significant bone marrow depression or pre-existing agranulocytosis
Adverse Reactions
- Agranulocytosis (potentially fatal, monitor CBC)
- Aplastic anemia and thrombocytopenia
- Hepatotoxicity (cholestatic jaundice, hepatitis)
- Arthralgia, myalgia, and skin rash/pruritus
- Lupus-like syndrome
Drug Interactions
- Anticoagulants (coumarin/indandione derivatives): May increase anticoagulant effect
- Beta-blockers: Clearance may decrease as hyperthyroidism is corrected
- Radioactive iodine: May decrease uptake of iodine
- Bone marrow depressants: Increased risk of myelosuppression
Curated Content: Needs Vetting Before Put to Clinical Use