Neonatal Drug Therapy Manual


Disclaimer: Official controlled document is the CHEO and Ottawa Hospital online copy. It is the responsibility of user to ensure that any paper copy version is the same as the online version before use.

Alternate Name(s): 
Eltroxin, Synthroid
Thyroid Supplement
Original Date: 
December 2008
Revised Date: 
March 2016
  • Replacement or supplemental therapy in congenital hypothyroidism
  • PO
    • Administer on an empty stomach at least 4 hours apart from calcium, iron and antacids
  • IV direct: over 2 - 5 minutes (max 100 mcg/min)




  • Initial starting dose:
    • 0 - 3 months: 10 - 15 mcg/kg/day once daily
    • 3 - 6 months: 8 - 10 mcg/kg/day once daily
  • Available as 25 mcg tablet.  Round dose to the nearest 1/4 tablet


  •  50 to 75% of the oral dose


  • Infants and neonates with very low or undectable serum T4 levels should be started at higher end of the dosage range
  • A lower dose should be considered for neonates at risk of cardiac failure, increasing every few days until a full maintenance dose is reached
  • The dose should be adjusted based on clinical response and laboratory parameters
Side Effects: 

Adverse reactions associated with levothyroxine sodium are primarily those of hyperthyroidism due to therapeutic overdosage

  • CVS: palpitations, tachycardia, cardiac arrythmias, hypertension
  • Dermatologic: hair loss
  • GI: diarrhea, vomiting
Parameters to Monitor: 
  • BP, HR
  • Measure TSH and free T4 two weeks after initiation of therapy and then at 2, 3, 6, 9 and 12 months of age in the first year of life. Titrate dose to normalize TSH and free T4 with follow-up measurements of TSH, free T4 at 4-6 weeks after dose adjustment.
Reconstitution and Stability: 
  • Levothyroxine 500 mcg (PPC)
    • Add 5 mL of 0.9% NaCl
    • Final concentration : 100 mcg/mL
  • Solution Compatible: 0.9% NaCl
  • Soybean formula decreases the absorption of levothyroxine

1.       Lau.E (Editor).  Drug Handbook and Formulary  - The Hospital for Sick Children.  Toronto; 2015

2.       Taketomo CK, Hodding JH, Kraus DM.  Pediatric Dosage Handbook.  22nd Edition.  Hudson: Lexi-Comp Inc.; 2015

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