Name: Methimazole (Tapazole)
Class: Antithyroid Drug (Thioamide)
Mechanism: Blocks thyroid synthesis.
Absorption: Oral ® 80-95% bioavailability.
Dist.: 0% protein binding. High placental transfer. 100% transfer into milk.
Metabolism.: Conjugated to gluconamide.
Excretion, t½: <10% style=""> 3-5 hr.
Toxicity/S.E.s: 7% freq. of untoward rxns. Most common = rash. 0.12% develop agranulocytosis. Occurs suddenly in first months of therapy, preceded by a sore throat and fever. Unusual bleeding and bruising may occur. C/i in nursing mothers, but can be used (w/great caution) in pregnancy-complicated hyperthyroidism (may cause neonatal goiter); PTU is safer.
Utility: Treat hyperthyroidism, but relapse after single course ³ 50%.
Special Features: 5-10 mg/8 hr (or higher).