Name: Propylthiouracil (PTU)
Class: Antithyroid Drug (Thioamide)
Mechanism: Blocks thyroid synthesis.
Absorption: Oral ® 80-95% bioavailability.
Dist.: 80% protein binding. Poor placental transfer. 10% transfer into milk.
Metabolism.: Conjugated to gluconamide.
Excretion, t½: 35% excreted in urine, mostly as gluconamide. 1-2 hr.
Toxicity/S.E.s: 3% freq. of untoward rxns. Most common = rash. 0.44% 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).
Utility: Treat hyperthyroidism, but relapse after single course ³ 50%.
Special Features: 75-100 mg/8 hr (or higher).