Methimazole / Tapazole

Antithyroid drugs - also referred to as thionamides - --are medications that treat an overactive thyroid (hyperthyroidism) by blocking the thyroid gland's ability to produce thyroid hormone. In the treatment of an overactive thyroid, which most commonly results from the autoimmune condition known as Graves' disease, it is critical to slow down the gland's excess production of thyroid hormones, especially the hormones thyroxine (T4) and triiodothyronine (T3).

Antithyroid drugs work by making it more difficult for the body to use iodine, thereby blocking the formation of thyroid hormones in the gland.

Antithyroid drug therapy is one of the treatments for hyperthyroidism and Graves' disease. The other treatments include radioactive iodine (RAI) ablation and surgical removal of all or part of the thyroid gland.

There are two key antithyroid drugs currently available in the United States: propylthiouracil (PTU) and methimazole. In the United States, methimazole is considered the preferred antithyroid drug in most situations.

Methimazole, sometimes called thiamazole, inhibits the thyroid from using iodine to produce thyroid hormone. It is generally taken as a dose once per day.

The drug is used around the world. In the United States, Tapazole is the only brand name of the antithyroid drug methimazole. There are a number of generic manufacturers of methimazole.

Tapazole

Tapazole is the brand name of methimazole, an antithyroid drug manufactured by King Pharmaceuticals, Inc. The FDA approved Tapazole in 2000.

• King Pharmaceuticals Website
• Prescribing information

Tapazole Ingredients: methimazole USP; lactose monohydrate; magnesium stearate; starch (corn); pregelatinized starch; and talc.

Strengths Available: 5 mg and 10 mg

Generic Methimazole (by Sandoz)

Sandoz, a member of the Novartis Group of Companies, manufactures a generic methimazole. It was approved by the FDA in 2001.

• Sandoz Website
• Prescribing information

Sandoz Methimazole Ingredients: methimazole USP; lactose monohydrate; magnesium stearate; starch (corn); and talc.

Strengths Available: 5 mg and 10 mg

Generic Methimazole (by Cedar Pharmaceuticals LLC)

Cedar Pharmaceuticals LLC manufacturers a generic methimazole that is distributed by United Research Laboratories. FDA approval was obtained in 2005.

• Cedar Pharmaceuticals Website
• Prescribing information

Cedar Pharmaceuticals Methimazole Ingredients: methimazole USP; actose monohydrate; magnesium stearate; potato starch; and talc.

Strengths Available: 5 mg, 10 mg, 15 mg, 20 mg

Generic Methimazole (by Activis Totowa)

Activis Totowa LLC manufacturers generic methimazole, and FDA approval was obtained in 2007.

• Activis Website
• Prescribing Information

Activis Methimazole Ingredients methimazole USP; lactose monohydrate; magnesium stearate; starch pregelatinized; and talc.

Strengths available: 5 mg and 10 mg

Generic Methimazole (by Caraco Pharmaceutical Laboratories)

Caraco Pharmaceutical Laboratories, Ltd. manufactures a generic methimazole that was approved by the FDA in 2007.

• Caraco Website
• Prescribing Information (PDF)

Caraco Methimazole Ingredients: methimazole USP; lactose monohydrate; povidone; talc; croscarmellose; magnesium stearate; and corn starch.

Strengths Available: 5mg and 10mg

Generic Methimazole (by Par Pharmaceutical Companies)

Par Pharmaceutical Companies manufactures a generic methimazole.

• Par Pharmaceutical Website
• Prescribing Information

Ingredients: methimazole USP; lactose monohydrate; magnesium stearate; corn starch; and talc.

Strengths Available: 5 mg and 10 mg

_Sources:

_{Daily Med, U.S. Food and Drug Administration medication Database, Online}

_{FDA Drug Safety Communication: New Boxed Warning on severe liver injury with propylthiouracil, April 21, 2010 Online}

_{Ross, Douglas MD, "Patient information: Antithyroid drugs," UpToDate. Last updated: November 13, 2009}

Additional reporting by: Leslie Blumenberg