Each tablet contains 5 mg (43.8 μmol) methimazole, an orally administered antithyroid drug. The molecular weight is 114.16, and the empirical formula is C4H6N2S.
Methimazole Tablets, USP (1-methylimidazole-2-thiol) is a white, crystalline substance that is freely soluble in water. It differs chemically from the drugs of the thiouracil series primarily because it has a 5- instead of a 6-membered ring.