Trade Names:Thyrolar ¼- Tablets 3.1 mcg T 3 /12.5 mcg T 4 (thyroid equivalent to 15)
Trade Names:Thyrolar ½- Tablets 6.25 mcg T 3 /25 mcg T 4 (thyroid equivalent to 30)
Trade Names:Thyrolar 1- Tablets 12.5 mcg T 3 /50 mcg T 4 (thyroid equivalent to 60)
Trade Names:Thyrolar 2- Tablets 25 mcg T 3 /100 mcg T 4 (thyroid equivalent to 120)
Trade Names:Thyrolar 3- Tablets 37.5 mcg T 3 /150 mcg T 4 (thyroid equivalent to 180)
Increases metabolic rate of body tissues; is needed for normal growth and maturation.
40% to 80% of T 4 is absorbed; absorption is increased by fasting and decreased by certain foods. Approximately 95% of T 3 is absorbed in 4 h.
More than 99% is bound to serum proteins. Minimal amounts excreted in breast milk.
Approximately 80% of T 3 comes from monodeiodination of T 4 . Conjugated hormone is found in the bile and gut where it may undergo enterohepatic circulation.
Primarily eliminated by the kidneys. Approximately 20% of T 4 is excreted in feces.
T 4 absorption and urinary excretion are decreased with age.
Replacement or supplemental therapy in hypothyroidism; pituitary TSH suppression in treatment or prevention of various types of euthyroid goiters, including thyroid nodules, subacute or chronic lymphocytic thyroiditis (Hashimoto's), multinodular goiter, and management of thyroid cancer; diagnostic agent in suppression tests to differentiate suspected and hyperthyroidism or thyroid gland autonomy.
Diagnosed but uncorrected adrenal cortical insufficiency; untreated thyrotoxicosis; apparent hypersensitivity to any component of the product.
PO Start with low doses, with increments depending on the CV status. Usual starting dose is 1 tablet of Thyrolar ½ with increments of 1 tablet of Thyrolar ¼ every 2 to 3 wk. In patients with long-standing myxedema, the recommended starting dose is 1 tablet daily of Thyrolar ¼ and reduce dosage if angina occurs. Readjust dosage within first 4 wk of therapy after proper clinical and laboratory evaluations, including serum levels of T 4 (bound and free) and TSH.Congenital HypothyroidismChildren (older than 12 yr of age)
PO More than 18.75 mcg of T 3 and 75 mcg T 4 daily.Children (6 to 12 yr of age)
PO 12.5 mcg of T 3 and 50 mcg T 4 to 18.75 mcg of T 3 and 75 mcg T 4 daily.Children (1 to 5 yr of age)
PO 9.35 mcg of T 3 and 37.5 mcg of T 4 to12.5 mcg of T 3 and 50 mcg T 4 daily.Children (6 mo to 12 mo)
PO 6.25 mcg of T 3 and 25 mcg of T 4 to 9.35 mcg of T 3 and 37.5 mcg of T 4 daily.Children (0 mo to 6 mo)
PO 3.1 mcg of T 3 and 12.5 mcg of T 4 to 6.25 mcg of T 3 and 25 mcg of T 4 daily.Thyroid CancerAdults
PO Larger amounts of thyroid hormone than those used for replacement therapy are required.Diagnostic AgentAdults
PO Usual suppressive dose of T 4 is 1.56 mcg/kg/day for 7 to 10 days.
Administer prescribed dose once daily. When given on an empty stomach, absorption is increased. However, to maintain steady blood levels and effect, be consistent in administering drug with or without food.
Store tablets in refrigerator (36° to 46°F).
May increase anticoagulant effect.Cholestyramine, colestipol
Bind T 3 and T 4 in the intestine, impairing absorption.Estrogens, oral contraceptives
Thyroid requirement may be increased in patients with nonfunctioning thyroid gland or receiving thyroid replacement therapy.Insulin, oral hypoglycemics
Requirements of these agents may be increased by liotrix.
Consider changes in thyroid binding globulin concentration when interpreting thyroxine (T 4 ) and triiodothyronine (T 3 ) values; medicinal or dietary iodine interferes with all in vivo tests of radioiodine uptake, producing low uptakes that may not reflect true decrease in hormone synthesis.
Hypermetabolic state (indicative of hyperthyroidism).
Monitor blood sugar in diabetic patient when drug is started or dose is changed.Development baseline tests
Monitor height, weight, and intellectual function in children to document normal development.Thyroid function tests
Ensure that thyroid function tests (eg, TSH, T 4 ) are determined prior to starting therapy and periodically during treatment.
Category A .
Minimal amounts excreted in breast milk.
When used for congenital hypothyroidism, routine determinations of serum T 4 or TSH are strongly advised in newborns.
Use with great caution in patients with CV disease, especially if integrity of coronary arteries is suspected, including patients with angina pectoris or the elderly; may aggravate intensity of symptoms in patients with diabetes mellitus or insipidus or adrenal cortical insufficiency.
Requires simultaneous administration of glucocorticoids.
Should not be used for weight reduction; may produce serious or life-threatening toxicity particularly when given with sympathomimetics or anorexiants.
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