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Thyroid Medications (cont.)

Anti-thyroid Medications

These medicines are used to treat an overactive thyroid gland by decreasing the output of thyroid hormone from the thyroid.

Propylthiouracil (also called PTU)

  • PTU blocks the production of thyroid hormone inside the thyroid gland
  • PTU is usually given in divided doses, 2 to 3 times a day
  • Blood levels of thyroid hormone do not drop until the stores of thyroid hormone in the thyroid are depleted, typically after 2-4 weeks
  • Thyroid hormone levels may take 1 to 4 months to normalize
  • Mild side effects include rash, low grade fevers, and itchiness
  • Rare but serious side effects include a reduction in white blood cells, which can prevent the body from fighting off an infection, and hepatitis (liver damage).
  • Recent studies have shown there is more liver toxicity with PTU and so now, Methimazole is usually the drug of choice. PTU is still preferred by some in pregnancy even though there are more minor birth defects seen with it.

Methimazole (Tapazole)

  • Similar mechanism and delay of action as PTU
  • Tapazole can be taken once each day
  • Tapazole has similar side effects to PTU

Blood levels of thyroid hormones should be checked every 4 to 6 weeks until hormone levels stabilize

Medically Reviewed by a Doctor on 12/2/2015

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