Antithyroid Drugs are a class of mediations, Thioamide class, that blocks the binding of iodine.

This class is regarded as a hormone antagonist and it directly affects thyroid hormones.

Essentially this group of medications affects overactive thyroid.

Antithyroid drugs decrease the levels of the two hormones produced by the thyroid:

1.)  Thyroxine (T4)

2.)  Triiodothyronine (T3)




  • Methimazole
  • Propylthiouracil  (PTU)
  • Carbimazole  –  [found in the United Kingdom]




Side Effects:

  • Agranulocytosis  [a decrease of white blood cells] –  seen more often with PTU but can also be seen in methimazole
  • Aplastic anemia
  • Sore throat
  • Fever
  • Rash


Use During Pregnancy:

  • Propylthiouracil (PTU) used to be the drug of choice during pregnancy
  • This was because it was believed to cause less severe birth defects than methimazole.
  • Current recommendations for propylthiouracil is that it be used during the first trimester only.
  • Rare liver damage has been seen in some people.
  • After the first trimester, women should switch to methimazole for the rest of the pregnancy.
VN:F [1.9.22_1171]
Rating: 0.0/10 (0 votes cast)
VN:F [1.9.22_1171]
Rating: 0 (from 0 votes)