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  • Type: Antithyroid
  • Dosage Forms:
  • Routes of Administration:
  • Other common names: PTU

Adult Dosing

  • Thyroid storm: 500-1000mg PO loading dose, followed by 250mg PO q4h
  • Hyperthyroidism
    • Initial: 50-300mg PO TID (based on severity)
    • Maintenance: 50mg PO TID
    • 1st trimester pregnancy: Use lowest dose needed to keep maternal total T3/T4 slightly above normal range for pregnancy, TSH suppressed, and free T4 at or slightly above upper limit of normal for nonpregnant women. Switch to methimazole for 2nd-3rd trimester

Pediatric Dosing

  • >6yo: 50 mg PO daily, carefully uptitrated

Special Populations


  • Allergy to class/drug

Adverse Reactions


Both PTU and methimazole can cause agranulocytosis and hepatotoxicity, but to a lesser extent with methimazole

  • Agranulocytosis, aplastic anemia
  • Hepatotoxicity, liver failure
  • Nephritis
  • Vasculitis


  • Rash


  • Half-life: 0.9-4.3h
  • Metabolism: Hepatic
  • Excretion: Renal

Mechanism of Action

  • Inhibits thyroperoxidase, blocking thyroid hormone synthesis in the thyroid. In target tissues, blocks 5'-deiodinase, thereby inhibiting conversion of T4 to active T3


See Also