Brand Names: Armour Thyroid
Tablets (Armour)*: 15 mg (¼ grain), 30 mg (½ grain), 60 mg (1 grain), 90 mg (1.5 grain), 120 mg (2 grain), 180 mg (3 grain), 240 mg (4 grain), 300 mg (5 grain)
Tablets (other brands): 16.25 mg, 32.5 mg, 648.75 mg, 65 mg, 81.25 mg, 97.5 mg, 113.75 mg, 130 mg, 146.25 mg, 162.5 mg, 195 mg, 260 mg, 325 mg
*Corresponding grain measurements are approximately
Adult hypothyroidism of any etiology:
Initial: 15-30 mg/day for two weeks, increase by 15 mg increments every 2-3 weeks. Individualize dosage as needed.
Maintenance: 60-180 mg/day.
Congenital hypothyroidism (children):
0-6 months old: 4.8-6 mg/kg/day.
6-12 months old: 3.6-4.8 mg/kg/day.
1-5 years old: 3-3.6 mg/kg/day.
Treatment or prevention of various type of euthyroid or multinodular goiters, including thyroid nodules, subacute or chronic lymphocytic thyroiditis, and in the management of thyroid cancer: Larger doses than those used for replacement are required.
*In acute emergency situations (when the oral route is not feasible) use levothyroxine injection as follows:
Treatment of Myxedema Coma: 0.4 mg of levothyroxine given rapidly intravenously, followed by daily supplements of 0.1-0.2 mg given intravenously. Resume oral therapy as soon as the clinical situation is stabilized, and the patient can take the oral dose.
Thyroid suppression therapy: 1.56 mg/kg/day of levothyroxine (T4) for 7-10 days.
Pharmacology/Pharmacokinetics:
The exact mechanism for thyroid is unknown although it is thought to be due to protein synthesis control, resulting in: (1) a regulation of growth and development, (2) an increase in metabolic rate, (3) inhibition of the secretion of thyrotropin by the pituitary, and (4) various effects on lipid and carbohydrate metabolism.
Drug Interactions:
May increase the hypothrombinemia effect of oral coagulants. Cholestyramine may decrease absorption. May decrease the therapeutic effect of digitalis or hypoglycemic agents. Free levothyroxine may be decreased when given with estrogens.
Contraindications/Precautions:
Use is contraindicated in patients with diagnosed but as yet uncorrected adrenal cortical insufficiency, untreated thyrotoxicosis, and in patients hypersensitive to any ingredient Use with caution in nursing mothers, in patients with cardiovascular disorders (such as angina pectoris), or diabetes, and in patients currently taking oral anticoagulants. Pregnancy Category A.
Adverse Effects:
Adverse effects other than those indicative of overdosage are rare. These include weight loss, palpitations, nervousness, diarrhea or abdominal cramps, sweating, tachycardia, angina pectoris, headache, insomnia, and intolerance to heat.
Do not discontinue therapy without first consulting physician.
Notify physician if signs of hyperthyroidism (overdose) occur.
Transient loss of hair may be seen in children, but recovery usually occurs.
Store in a cool, dry place away from sunlight and children.
If a dose is missed, take it as soon as possible. If it is closer to the time of your next dose than the dose you missed, skip the missed dose and return to your dosing schedule. Do not double doses.
Contact a physician if the above side effects are severe or persistent.
