Liothyronine Sodium (T3, Triiodithyronine)(lye’ oh thye’ roe neen)
Cytomel, Triostat
PREGNANCY CATEGORY A
Drug class
Thyroid hormone
Therapeutic Actions
Increases the metabolic rate of body tissues, thereby increasing oxygen consumption; respiratory and HR; rate of fat, protein, and carbohydrate metabolism; and growth and maturation.
Indications
Replacement therapy in hypothyroidism
Pituitary TSH suppression in the treatment and prevention of euthyroid goiters and in the management of thyroid cancer
Thyrotoxicosis in conjunction with antithyroid drugs and to prevent goitrogenesis, hypothyroidism, and thyrotoxicosis during pregnancy
Synthetic hormone used with patients allergic to desiccated thyroid or thyroid extract derived from pork or beef
Diagnostic use: T3 suppression test to differentiate suspected hyperthyroidism from euthyroidism
IV: Treatment of myxedema coma and precoma
Contraindications and Cautions
Contraindicated with allergy to active or extraneous constituents of drug, untreated thyrotoxicosis, and acute MI uncomplicated by hypothyroidism.
Use cautiously with Addison disease (treat hypoadrenalism with corticosteroids before thyroid therapy), lactation, patients with coronary artery disease or angina, pregnancy.
Available Forms
Tablets—5, 25, 50 mcg; injection—10 mcg/mL
Dosages
15–37.5 mcg equals approximately 60 mg (1 grain) desiccated thyroid.
Adults
Hypothyroidism: Initial dosage, 25 mcg/day PO. May be increased every 1–2 wk in increments of 12.5–25-mcg. For maintenance, 25–75 mcg/day.
Myxedema: Initial dosage, 5 mcg/day PO. Increase in increments of 5–10 mcg every 1–2 wk. For maintenance, 50–100 mcg/day.
Myxedema coma and precoma: 25–50 mcg IV every 4–12 hr; do not give IM or subcutaneously. In patients with cardiac disease, start at 10–20 mcg IV. Do not exceed 100 mcg/24 hr.
Simple goiter: Initial dosage, 5 mcg/day PO. May be increased by increments of 5–10 mcg every 1–2 wk. For maintenance, 75 mcg/day.
T3 suppression test: 75–100 mcg/day PO for 7 days, then repeat iodine 131 (I131) uptake test. 131I uptake will be unaffected in the hyperthyroid patient but will be decreased by 50% or more in the euthyroid patient.
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