Methimazole inhibits the thyroid from using iodine to produce thyroid hormone. It is generally taken once a day.
Methimazole is sometimes called thiamazole. It is used around the world and is the primary antithyroid drug used in the United States, where it it is available as the brand Tapazole.
Several manufacturers also offer a generic form of Methimazole.
Carbimazole is converted into the drug methimazole in the body, and is therefore quite similar in action. The most well-known brand of carbimazole is Neomercazole.
Neomercazole is a trademarked brand name of carbimazole and is manufactured by Amdipharm International (UK). The drug was authorized in 2004, and is sold in the UK and Europe, but is not available in the United States.
Neomercazole Ingredients: carbimazole Ph.Eur; lactose; maize starch; sucrose; magnesium stearate; sucrose; talc; gum acacia; ferric oxide; propyl hydroxybenzoate; and gelatin.
Available Strengths: 5 mg
Other Brands/Names: Carbimazole is available in some European and Asian countries under the following brand names: Atirozidina, Basolest, CG1, Carbimazol Spofa, Carbotiroid, Mertiran, Neo-Mercazole, Neo-Thyreostat, Neo-Tireol, and Tyrazol.
PTU has more side effects than the other drugs discussed here, and it is the drug of choice for hyperthyroidism in a few situations (during early pregnancy, severe thyroid storm and in the event of serious side effects due to methimazole).
Only generic PTU is available; there are no brand names of PTU marketed in the United States. A number of manufacturers produce generic PTU.
PTU is available outside of the United States under a number of different brand names, including: Biolab Propiltiouracil; Propiltiouracil; Propiltiouracilo; Propycil; Propyl; Propyl-Thiocil; Propylthiouracil DHA; Propylthiouracile AP-HP; Propylthiouracile; Propylthiouracil Evans; Propylthiouracil Lederle; Propyl-Thyracil; Propyltiouracil Medic; Prothiucil; Thyreostat II; Thyrosan; Tiotil; Tirostat and Uracil.
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, 2009Additional reporting by: Leslie Blumenberg