Methimazole is effective in treating hyperthyroidism. Methimazole can inhibit the enzyme peroxidase in the thyroid gland, thus hindering the oxidation of iodide and the coupling of tyrosine in the thyroid gland, and hindering the synthesis of thyroxine and triiodothyronine, thus achieving the purpose of treating hyperthyroidism. Adverse reactions such as arthralgia, dizziness and rash may occur after use of the drug, which usually resolve gradually after discontinuation of the drug. This drug is contraindicated in persons who are allergic to the components of the drug. It is contraindicated in persons with moderate to severe neutropenia, in persons with preexisting cholestasis that is not caused by hyperthyroidism, and in persons who have had granulocyte deficiency or severe bone marrow suppression following treatment with methimazole or carbimazole or propylthiouracil. Methimazole should be used as prescribed by a physician.