GENERIC NAME: methimazole
BRAND NAME: Tapazole, Northyx
DRUG CLASS AND MECHANISM: Methimazole is used to treat an overactive thyroid gland (hyperthyroidism). Grave's disease is the most common cause of hyperthyroidism. Grave's disease is an autoimmune disease resulting from antibodies that attach to receptors on thyroid hormone-producing cells in the thyroid gland and trigger overproduction of thyroid hormone. An enzyme (peroxidase) produces thyroid hormones, i.e., thyroxine (T4) and triiodothyronine (T3), by combining iodine with a protein called thyroglobulin. Methimazole prevents iodine and peroxidase from their normal interactions with thyroglobulin to form T4 and T3. This action decreases thyroid hormone production. Methimazole also interferes with the conversion of T4 to T3. Since T3 is more potent than T4, this also reduces the activity of thyroid hormones. The FDA approved methimazole in March 1999.
GENERIC AVAILABLE: Yes
PREPARATIONS: Tablet: 5, 10 mg
STORAGE: Methimazole should be stored at room temperature, 15 C and 30 C (59 F and 86 F).
PRESCRIBED FOR: Methimazole is used for treating hyperthyroidism. It also is used for decreasing symptoms of hyperthyroidism in preparation for surgical removal of the thyroid gland or before inactivating the thyroid gland with radioactive iodine. Long-term use of methimazole may lead to a remission of the hyperthyroidism.
DOSING: The initial adult dose of methimazole is:
- 15 mg/day for mild hyperthyroidism
- 30-40 mg/day for moderately severe hyperthyroidism
- 60 mg/day for severe hyperthyroidism
The daily dose is divided into three doses administered every 8 hours.
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