Methimazole (also known as Tapazole or Thiamazole or MMI) CAS 60-56-0 is an antithyroid drug, and part of the thioamide group. Like its counterpart propylthiouracil,a major side effect of treatment is agranulocytosis.
Methimazole prevents the thyroid gland from producing too much thyroid hormone. Methimazole is used to treat hyperthyroidism (overactive thyroid). It is also used before thyroid surgery or radioactive iodine treatment.
Methimazole may also be used for other purposes not listed in this medication guide.
Appearance White to yellowish crystalline powder
Melting point 144~146°C
Loss on drying ≤0.5%
Residue on ignition ≤0.1%
Residual Solvents Methanol ≤0.3%Assay ≥98.5%
Methimazole is a drug used to treat hyperthyroidism, a condition that occurs when the thyroid gland begins to produce an excess of thyroid hormone. The drug may also be taken before thyroid surgery to lower thyroid hormone levels and minimize the effects of thyroid manipulation. Additionally, Methimazole is used in the veterinary setting to treat hyperthyroidism in cats.
Mechanism of action
Methimazole inhibits the enzyme thyroperoxidase, which normally acts in thyroid hormone synthesis by oxidizing the anion iodide (I-) to iodine , facilitating iodine's addition to tyrosine residues on the hormone precursor thyroglobulin, a necessary step in the synthesis of triiodothyronine (T3) and thyroxine (T4).It does not inhibit the action of the sodium-dependent iodide transporter located on follicular cells' basolateral membranes. Inhibition of this step requires competitive inhibitors such as perchlorate and thiocyanate.