antithyroid drug /-thī″roid/ , a preparation that inhibits the synthesis of thyroid hormones and is commonly used in the treatment of hyperthyroidism. The major antithyroid drugs are thioamide derivatives, such as propylthiouracil, and methimazole. Such substances interfere with the incorporation of iodine into the tyrosyl residues of thyroglobulin required for the production of the hormones thyroxine and triiodothyronine. They are often used to control hyperthyroidism during an anticipated remission and before a thyroidectomy.
