Methimazole (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.
Each tablet contains 5 or 10 mg (43.8 or 87.6 µmol) methimazole, an orally administered antithyroid drug.
Each tablet also contains lactose monohydrate, magnesium stearate, starch (corn), pregelatinized starch and talc.
The molecular weight is 114.16, and the molecular formula is C4H6N2S. The structural formula is as follows: