Liothyronine Sodium

Patients on thyroid hormone preparations and parents of pediatric patients on thyroid therapy should be informed that:

Replacement therapy is to be taken essentially for life, with the exception of cases of transient hypothyroidism, usually associated with thyroiditis, and in those patients receiving a therapeutic trial of the drug.

They should immediately report during the course of therapy any signs or symptoms of thyroid hormone toxicity, e.g., chest pain, increased pulse rate, palpitations, excessive sweating, heat intolerance, nervousness, or any other unusual event.

In case of concomitant diabetes mellitus, the daily dosage of antidiabetic medication may need readjustment as thyroid hormone replacement is achieved. If thyroid medication is stopped, a downward readjustment of the dosage of insulin or oral hypoglycemic agent may be necessary to avoid hypoglycemia. At all times, close monitoring of urinary glucose levels is mandatory in such patients.

In case of concomitant oral anticoagulant therapy, the prothrombin time should be measured frequently to determine if the dosage of oral anticoagulants is to be readjusted.

Partial loss of hair may be experienced by pediatric patients in the first few months of thyroid therapy, but this is usually a transient phenomenon and later recovery is usually the rule.

Liothyronine is a man-made form of a hormone that is normally produced by your thyroid gland to regulate the body's energy and metabolism. Liothyronine is given when the thyroid does not produce enough of this hormone on its own.

Liothyronine treats hypothyroidism (low thyroid hormone). Liothyronine is also used to treat or prevent goiter (enlarged thyroid gland), and is also given as part of a medical tests for thyroid disorders.

Liothyronine should not be used to treat obesity or weight problems.

Liothyronine may also be used for purposes not listed in this medication guide.

Hypothyroidism

Used orally as replacement or supplemental therapy in congenital or acquired hypothyroidism of any etiology, except transient hypothyroidism during the recovery phase of subacute thyroiditis.a c Specific indications include primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) hypothyroidism.a c

Generally considered unsatisfactory for long-term use because of potential problems (i.e., wide swings in serum T3 concentrations, possibility of more pronounced adverse cardiovascular effects);a g o however, may be useful when absorption of levothyroxine is questionable, when impairment of peripheral conversion of thyroxine to triiodothyronine is suspected, or in patients allergic to natural thyroid hormone.a b c Levothyroxine is considered drug of choice for replacement therapy.e

For treatment of congenital hypothyroidism (cretinism), levothyroxine is considered drug of choice.a

Used IV for treatment of myxedema coma or precoma.a b c Preferred by some clinicians over levothyroxine when a rapid effect or rapidly reversible effect is desired; however, levothyroxine generally is considered drug of choice for this use.a

Pituitary TSH Suppression

Treatment or prevention of various types of euthyroid goiters, including thyroid nodules, subacute or chronic lymphocytic thyroiditis (Hashimoto’s thyroiditis), and multinodular goiter.a c

Adjunct to radioiodine therapy in the management of thyroid cancer†.o

Diagnosis of Thyroid Disorders

Used diagnostically in suppression tests to differentiate suspected mild hyperthyroidism or thyroid gland autonomy.a c d Use with caution in patients in whom there is a strong suspicion of thyroid gland autonomy because exogenous hormone effects will be additive to endogenous source.c

Drugs Affecting Hepatic Microsomal Enzymes

Potential increased metabolism of thyroid agent with drugs that induce hepatic microsomal enzymes resulting in increased thyroid agent dosage requirements.d

Drugs That May Decrease T4 5’-Deiodinase Activity

Inhibitors of T4 5’-deiodinase decrease peripheral conversion of T4 to T3, resulting in decreased T3 concentrations.d i u However, serum T4 concentrations usually remain within normal range but may occasionally be slightly increased.d i

Specific Drugs

Drugs Affecting Thyroid Function or Thyroid Function Tests

Various drugs or concomitant medical conditions (e.g., pregnancy, infectious hepatitis) may adversely affect thyroid function (e.g., alter endogenous thyroid hormone secretion, reduce TSH secretion) resulting in hypothyroidism or hyperthyroidism or interfere with laboratory tests used to assess thyroid function.b c d Consult specialized references for information.

Some drugs may affect transport of thyroid hormones (T3, T4) by affecting serum thyroxine-binding globulin (TBG) concentrations.d i However, free T4 concentrations may remain normal and the patient may remain euthyroid.d i

Drugs Affecting Thyroxine Binding Globulin Concentrationsb c d

Drugs That May Increase Serum TBG Concentration

• Estrogens, oral (including estrogen-containing oral contraceptives)b c d

• Fluorouracild

• Methadoned

• Mitotaned

• Tamoxifend

Drugs That May Decrease Serum TBG Concentration

• Androgensd

• Asparaginased

• Glucocorticoidsd

• Niacin (extended-release)d

• Thyroid hormones (T4 and T3) regulate multiple metabolic processes, including augmentation of cellular respiration and thermogenesis, as well as metabolism of proteins, carbohydrates, and lipids.b c d i

• Thyroid hormones also play an essential role in normal growth and development and normal maturation of the CNS and bone.b c d The protein anabolic effects of thyroid hormones are essential for normal growth and development.d i

• The physiologic actions of thyroid hormones are produced predominately by T3, most of which (approximately 80%) is derived from T4 by deiodination in peripheral tissues.a b d

• T3 is 4 times more potent than T4.i

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name