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levothyroxine sodium (L-thyroxine, T4)
Eltroxin (CA) (UK), Euthyrox (CA), Evotrox (UK), Levo-T, Levolet, Levothroid, Levoxyl, Nu-Thyro (CA), Soloxine, Synthroid, Unithroid
Pharmacologic class: Synthetic thyroxine hormone
Therapeutic class: Thyroid hormone replacement
Pregnancy risk category A
FDA Box Warning
• Drug shouldn't be used alone or with other agents to treat obesity or weight loss. In euthyroid patients, doses within range of daily hormonal requirements are ineffective for weight loss. Larger doses may cause serious or life-threatening toxicity, particularly when given with sympathomimetic amines (such as those used for anorectic effects).
Synthetic form of thyroxine that replaces endogenous thyroxine, increasing thyroid hormone levels. Thyroid hormones help regulate cell growth and differentiation and increase metabolism of lipids, protein, and carbohydrates.
Powder for injection: 200 mcg/vial in 6- and 10-ml vials, 500 mcg/vial in 6- and 10-ml vials
Tablets: 25 mcg, 50 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg, 175 mcg, 200 mcg, 300 mcg
⊘Indications and dosages
➣ Hypothyroidism; treatment or prevention of euthyroid goiter
Adults: For healthy adults younger than age 50 and those over age 50 who have recently been treated or undergone short-term therapy, start at full replacement dosage of 1.7 mcg/kg P.O. daily, given 30 minutes to 1 hour before breakfast. For patients older than age 50 or younger than age 50 with heart disease, 25 to 50 mcg P.O. daily, increased q 4 to 6 weeks. In severe hypothyroidism, initial dosage is 12.5 to 25 mcg P.O. daily, adjusted by 25 mcg daily q 2 to 4 weeks. For patients who can't tolerate oral doses, adjust I.M. or I.V. dosage to roughly half of oral dosage.
➣ Congenital hypothyroidism
Children older than age 12 who have completed puberty and growth: 1.7 mcg/kg P.O. daily
Children older than age 12 who have not completed puberty and growth: Up to 150 mcg or 2 to 3 mcg/kg P.O. daily
Children ages 6 to 12: 4 to 5 mcg/kg P.O. daily
Children ages 1 to 5: 5 to 6 mcg/kg P.O. daily
Infants ages 6 to 12 months: 6 to 8 mcg/kg P.O. daily