About propylthiouracila thioamide derivative, antithyroid drug.mechanism of action of propylthiouracilit is an antithyroid drug which inhibits thyroid hormone synthesis. it binds to thyroid peroxidase and inhibits oxidation of iodide or iodotyrosil residues. it inhibits iodination of tyrosine residues in thyroglobulin and prevents coupling of iodothyrosine residues to form t3 and t4. thyroid colloid depleted over time and blood levels of t3 &t4 are reduced. it also inhibits peripheral conversion of t4 tot3.indications for propylthiouracil1. hyperthyroidism (long term treatment) 2. prior to thyroidectomy 3. prior to radiotherapy 4. hepatic hyper metabolic state due to alcohol interactions for propylthiouraciloral anticoagulants: activity of oral anticoagulants may be potentiated.