Trade Names:Armour Thyroid- Tablets 15 mg (¼ grain)- Tablets 30 mg (½ grain)- Tablets 60 mg (1 grain)- Tablets 90 mg (1½ grain)- Tablets 120 mg (2 grain)- Tablets 180 mg (3 grain)- Tablets 240 mg (4 grain)- Tablets 300 mg (5 grain)
Trade Names:S-P-T- Capsules 60 mg (1 grain) (Pork thyroid suspended in soybean oil)- Capsules 120 mg (2 grain) (Pork thyroid suspended in soybean oil)- Capsules 180 mg (3 grain) (Pork thyroid suspended in soybean oil)- Capsules 300 mg (5 grain) (Pork thyroid suspended in soybean oil)
Trade Names:Thyrar- Tablets 30 mg (½ grain) (Bovine thyroid)- Tablets 60 mg (1 grain) (Bovine thyroid)- Tablets 120 mg (2 grain) (Bovine thyroid)
Trade Names:Thyroid Strong- Tablets 30 mg (½ grain) (50% stronger than thyroid USP. Each grain is eq. to 1½ grain of thyroid USP.)- Tablets 60 mg (1 grain) (50% stronger than thyroid USP. Each grain is eq. to 1½ grain of thyroid USP.)- Tablets 120 mg (2 grain) (50% stronger than thyroid USP. Each grain is eq. to 1½ grain of thyroid USP.)- Tablets 180 mg (3 grain) (50% stronger than thyroid USP. Each grain is eq. to 1½ grain of thyroid USP.)
Increases metabolic rate of body tissues.
Levothyroxine (T 4 ) is only partially absorbed from the GI tract. Absorption varies from 48% to 79%. Fasting increases absorption. Liothyronine (T 3 ) is almost totally absorbed (95%) in 4 h.
More than 99% is bound to serum proteins.
Deiodination of levothyroxine (T 4 ) occurs at a number of sites, including liver, kidney, and other tissues.
Replacement or supplemental therapy in hypothyroidism; TSH suppression (in thyroid cancer, nodules, goiters, and enlargement in chronic thyroiditis); diagnostic agent to differentiate suspected hyperthyroidism from euthyroidism.
Hypersensitivity to any ingredient; acute MI and thyrotoxicosis uncomplicated by hypothyroidism. Also contraindicated when hypothyroidism and hypoadrenalism (Addison disease) coexist, unless treatment of hypoadrenalism with adrenocortical steroids precedes initiation of thyroid therapy.
Optimal dosage determined by clinical response and laboratory findings.HypothyroidismAdults
PO 30 mg/day initially, increasing by 15 mg increments every 2 to 3 wk. In patients with long-standing myxedema, 15 mg/day, particularly if CV impairment is suspected. Reduce dosage if angina occurs.Maintenance
60 to 120 mg/day.Children
PO See table for recommended dose in congenital hypothyroidism.Congenital Hypothyroidism Dose Age Dose per day (mg) Daily dose per kg (mg) > 12 yr of age > 90 1.2 to 1.8 6 to 12 yr of age 60 to 90 2.4 to 3 1 to 5 yr of age 45 to 60 3 to 3.6 6 to 12 mo of age 30 to 45 3.6 to 4.8 0 to 6 mo of age 7.5 to 30 2.4 to 6 Thyroid Cancer
Larger doses required.
Store at room temperature in tightly closed container.
Anticoagulant effects may be increased.Cholestyramine
May decrease thyroid efficacy.Digitalis glycosides
Digitalis levels may increase, resulting in toxicity.Theophyllines
Theophylline Cl may be altered in hyperthyroid or hypothyroid patients.
Consider changes in thyroid-binding globulin concentration when interpreting T 4 and 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.
Palpitations; tachycardia; cardiac arrhythmias; angina pectoris; cardiac arrest.
Tremors; headache; nervousness; insomnia.
Hypersensitivity; weight loss; sweating; heat intolerance; fever.
Adverse reactions generally indicate hyperthyroidism caused by therapeutic overdosage.
Category A .
Excreted in breast milk.
Routine determinations of serum T 4 or TSH are strongly advised in newborns. Initiate treatment immediately on diagnosis and continue for life, unless transient hypothyroidism is suspected. In infants, excessive doses of thyroid hormone preparations may produce craniosynostosis. Children may experience transient partial hair loss in first few months of thyroid therapy.
Use caution when integrity of CV system, particularly coronary arteries is suspect (eg, angina, elderly). Development of chest pain or worsening CV disease requires decrease in dosage. Observe patients with coronary artery disease during surgery, since possibility of cardiac arrhythmias may be greater in those treated with thyroid hormones.
Therapy in patients with concomitant diabetes mellitus or insipidus or adrenal insufficiency (Addison disease) exacerbates intensity of symptoms. Therapy of myxedema coma requires simultaneous administration of glucocorticoids. In patients whose hypothyroidism is secondary to hypopituitarism, adrenal insufficiency, if present, should be corrected with corticosteroids before administering thyroid hormones.
May rarely precipitate hyperthyroid state or may aggravate existing hyperthyroidism.
Rule out before therapy.
Patients are particularly sensitive to thyroid preparations. Begin with small doses.
Should not be used for weight reduction; may produce serious or even life-threatening toxicity in larger doses, particularly when given with anorexiants.
Tachycardia, arrhythmias, hypertension, angina, fever, tremor, vomiting, diarrhea, insomnia, headache, seizures, coma.
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