• Type: Endocrine, synthetic hormone
  • Dosage Forms: Tablet 13mcg, 25mcg, 50mcg, 75mcg, 88mcg, 100mcg, 112mcg, 125mcg, 137mcg, 150mcg, 175mcg, 200mcg. IV 100mcg, 200mcg, 500mcg
  • Routes of Administration: PO, IV
  • Common Trade Names: Synthroid

Adult Dosing

Pediatric Dosing

  • Hypothyroid: Doses vary, 1.7-15 mcg/kg/day PO

Special Populations

  • Pregnancy Rating: A
  • Lactation risk: Infant risk minimal
  • Renal dosing: Not defined
  • Hepatic dosing: Not defined


  • Allergy to class/drug, hypersensitivity to glycerol
  • Uncorrected adrenal insufficiency (may precipitate acute adrenal crisis)
  • Acute MI
  • Subclinical or overt thyrotoxicosis, nontoxic diffuse goiter, nodular thyroid disease

Adverse Reactions


  • MI, heart failure, tachycardia, cardiac arrest
  • Pseudotumor, seizure
  • Dyspnea
  • Hyperthyroid
  • Decreased bone mineral density, hip fracture


  • Palpitations
  • Diarrhea
  • Anxiety, insomnia, fatigue, sweating, weight loss
  • Alopecia


  • Half-life: 6-7 days
  • Metabolism: Hepatic
  • Excretion: Renal, fecal

Mechanism of Action

  • Synthetic thyroid hormone (T4)

See Also


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