B. Antithyroid drugs a Thiourea derivatives e 1. Pharmacological effects ( Inhibiting the formation of thyroid hormones by interfering with iodination: inhibiting peroxidation, then the iodination and coupling 1 Symptom relieving: 2-3 weeks Basic metabolic rate returning 1-2 mints (2) Inibiting peripheral deiodination ofT T4>T3y (propylthiouracil) (3) Goitrogenic action(goiter)