Methimazole

An antithyroid medication.

Information about Methimazole

Methimazole is an antithyroid medication used in the therapy of hyperthyroidism and Graves disease. Methimazole has been linked to serum aminotransferase elevations during therapy as well as to a clinically apparent, idiosyncratic liver injury that is typically cholestatic and self-limited.

Mechanism of action of Methimazole

Methimazole (meth im' a zole), which is also known as thiamazole, is a thioamide and a thyroid hormone antagonist which acts by inhibiting the incorporation of iodine into tyrosyl residues of thyroglobulin and, thus, lowering thyroid hormone levels. Methimazole resembles propylthiouracil both in chemical structure and activity.

FDA approval information for Methimazole

Methimazole was introduced into use in 1954 and is still widely used for the temporary amelioration of hyperthyroidism in Graves disease, particularly in patients with mild or self-limited hyperthyroidism or who wish to avoid thyroidectomy or radiation therapy. Because of the hepatotoxicity of propylthiouracil which can be fatal, methimazole is now considered the first line treatment for hyperthyroidism when there is a need to avoid surgery or radioiodine therapy.

Brand name for Methimazole

Methimazole is available in generic forms and under the brand name of Tapazole as tablets of 5 and 10 mg.

Dosage and administration for Methimazole

The usual dose in adults is 15 to 60 mg daily in three divided doses until the patient is euthyroid, followed by a maintenance dose of 5 to 15 mg daily.

Side effects of Methimazole

Common side effects include gastrointestinal upset, headache, drowsiness, arthralgias, paresthesias, hair loss and rash. Rare complications of methimazole (<1%) include agranulocytosis, aplastic anemia, nephritis and hepatitis.

• Dailymed label info on Methimazole
• FDA Methimazole

Methimazole Resources
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