methimazole, Tapazole, Northyx (cont.)

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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.

The maintenance dose is 5-15 mg/day.

The usual initial children's dose is 0.4 mg/kg given in 3 divided doses administered 8 hours apart, and the maintenance dose is half the initial dose.

DRUG INTERACTIONS: Warfarin (Coumadin) works by reducing the activity of vitamin K and therefore the formation of vitamin K dependent clotting factors. Methimazole may increase the activity of warfarin by further reducing the activity of vitamin K in the body.

Hyperthyroidism increases elimination of beta blockers. Correcting hyperthyroidism will cause less elimination of beta blockers. Therefore, the dose of beta blockers may require reduction when hyperthyroidism is corrected. A similar reaction may also occur with digoxin (Lanoxin) and theophylline (Respbid, Slo-Bid, Theo-24, Theolair).

Medically Reviewed by a Doctor on 8/6/2014

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