DRUG | SUPPLIED | DOSE | COMMENTS |
---|---|---|---|
LEVOTHYROXINE SODIUM (Paeds) (Eltroxin, Synthroid, Thyroxine, T4) Mechanism of action: Synthetic thyroxine (T4) Ref: 1, 32 Last update: 2022-04-04 |
tablet: 25 mcg, 50 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 150 mcg, 200 mcg (also available but not stocked at BCCH: 137 mcg, 175 mcg, 300 mcg tablets) injection: 500 mcg/vial |
PO (full replacement doses): 0-3 mos.: 10-15 mcg/kg PO once daily 3-6 mos.: 8-10 mcg/kg PO once daily 6-12 mos.: 6-8 mcg/kg PO once daily. 1-5 yrs: 5-6 mcg/kg PO once daily 5-12 yrs: 4-5 mcg/kg PO once daily 12 yrs to adult: 2-3 mcg/kg PO once daily (average adult dose is 1.6 mcg/kg/24 hr) IV: Infants and Children: 50-75% of oral doses recommended above. IV dose should be reviewed with an endocrinologist if switching from PO to IV. |
Titrate doses at 2 to 4-week intervals initially, to obtain a mid-normal TSH level for primary hypothyroidism or free T4 level in the upper half of the normal range for secondary hypothyroidism, as well as a clinically euthyroid state. Thereafter, check levels every 3-6 months. Doses between available tablet sizes can be achieved by using 1/2 of a larger tablet (e.g. 1/2 of a 75-mcg tablet to give 37.5 mcg). Different brands can be interchanged as per the College of Pharmacists of BC's 2004 policy. However, if a patient has been on levothyroxine previously, it is preferable to continue the therapy with the same brand. If a different brand is dispensed, suggest monitoring TSH and/or free T4 levels. Very unstable in solution; if oral liquid must be given, administer dose immediately after mixing. Levothyroxine has a very long half-life (6-7 days); patients on chronic therapy can go without a dose for up to 7 days if they are NPO for any reason. Standard Prescription: levothyroxin__mcg PO once daily (__mcg/kg/24hr) |