Levothyroxine Sodium (levothyroxine sodium)

The dosage of levothyroxine sodium for hypothyroidism or pituitary TSH suppression depends on a variety of factors, including patient age, body weight, cardiovascular status, concomitant medical conditions (including pregnancy), concomitant medications, co-administered food, and the specific nature of the condition being treated. Dosage must be individualized to account for these factors, with dosage adjustments made based on periodic assessment of the patient's clinical response and laboratory parameters.

Levothyroxine sodium is administered orally or by IV injection. It is available for oral administration as a tablet, capsule, or oral solution; approved oral preparations may not be therapeutically equivalent to one another (consult the FDA's Approved Drug Products with Therapeutic Equivalence Evaluations (Orange Book) for current information). Levothyroxine sodium is available for IV administration as a solution for injection or a powder for reconstitution and injection.

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There is no enhanced messaging for this drug.

There are no contraindication interactions for this drug.

There are no severe interactions for this drug.

There are no moderate interactions for this drug.

*Uncorrected adrenal insufficiency.

*Hypersensitivity to glycerol (Tirosint-SOL(R) only).

*Hypersensitivity to glycerin and edetate disodium (Ermeza(R) only).

There are no contraindication contraindications for this drug.

There are no severe contraindications for this drug.

There are no moderate contraindications for this drug.

Adverse reactions associated with oral levothyroxine are primarily those of hyperthyroidism due to therapeutic overdosage, including arrhythmia, myocardial infarction, dyspnea, muscle spasm, headache, nervousness, irritability, insomnia, tremors, muscle weakness, increased appetite, weight loss, diarrhea, heat intolerance, menstrual irregularities, and skin rash.

Adverse reactions associated with IV levothyroxine are also primarily those of hyperthyroidism due to therapeutic overdosage, including fatigue, increased appetite, weight loss, heat intolerance, fever, excessive sweating, headache, hyperactivity, nervousness, anxiety, irritability, emotional lability, insomnia, tremors, muscle weakness, muscle spasm, palpitations, tachycardia, arrhythmias, increased pulse and blood pressure, heart failure, angina, myocardial infarction, cardiac arrest, dyspnea, diarrhea, vomiting, abdominal cramps, elevations in liver function tests, flushing, and rash.

There are no severe adverse reactions for this drug.

There are no less severe adverse reactions for this drug.

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Safety and effectiveness of levothyroxine tablets and oral solution have been established for use as replacement therapy for primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) congenital or acquired hypothyroidism in pediatric patients from birth to <17 years of age. Safety and effectiveness have also been established for use as an adjunct to surgery and radioiodine therapy for management of thyrotropin-dependent well-differentiated thyroid cancer in pediatric patients from birth to <17 years of age.

Safety and effectiveness of levothyroxine oral capsules have been established in pediatric patients >=6 years of age.

Rapid restoration of normal serum T4 concentrations in patients with congenital hypothyroidism is essential for preventing adverse effects on cognitive development or overall growth and maturation. Levothyroxine therapy should be initiated immediately upon diagnosis; it is typically continued for life in patients with congenital hypothyroidism.

In pediatric patients without an established diagnosis of permanent hypothyroidism, discontinue levothyroxine for a trial period (after the patient is at least 3 years of age) and obtain serum T4 and TSH levels at the end of the trial period; use laboratory test results and clinical assessments to guide diagnosis and treatment, if warranted.

Closely monitor infants and children for cardiac overload, arrhythmia, and aspiration from avid suckling during the first 2 weeks of levothyroxine therapy.

Levothyroxine oral solutions contain glycerin or glycerol. These inactive ingredients may cause GI irritation resulting in vomiting and/or osmotic diarrhea; patients in the first 3 months of life may be particularly susceptible to serious fluid and electrolyte complications from glycerin- or glycerol-induced GI irritation. Closely monitor patients from birth to 3 months of age for signs and symptoms of GI irritation.

Safety and effectiveness of IV levothyroxine have not been established in pediatric patients.

Clinical experience, including data from published postmarketing studies, has not identified increased rates of major birth defects, miscarriages, or other adverse maternal or fetal outcomes in pregnant women treated with oral levothyroxine to maintain a euthyroid state. Maternal hypothyroidism during pregnancy may increase the risk of complications, including spontaneous abortion, gestational hypertension, pre-eclampsia, stillbirth, and premature delivery. Untreated maternal hypothyroidism may also adversely affect fetal neurocognitive development. Levothyroxine should not be discontinued during pregnancy, and hypothyroidism diagnosed during pregnancy should be promptly treated.

Because thyroid-stimulating hormone (TSH) levels may increase during pregnancy, levothyroxine requirements may also be increased; TSH should be monitored, and the dosage of levothyroxine should be adjusted as necessary. Postpartum TSH levels are similar to preconception values, so the levothyroxine dosage should be decreased to the pre-pregnancy dosage immediately after delivery.

There are no reported cases of IV levothyroxine being used to treat myxedema coma in pregnant patients; however, because nontreatment is associated with a high probability of significant morbidity or mortality to the maternal patient and the fetus, pregnant patients who develop myxedema should be treated with IV levothyroxine.

Published studies report that levothyroxine is present in human milk following oral administration. No adverse effects on the breast-fed infant have been reported. The effects of levothyroxine on milk production are not known; however, adequate levothyroxine treatment during lactation may normalize milk production in hypothyroid lactating mothers with low milk supply.

The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for the drug and any potential adverse effects on the breast-fed infant from levothyroxine or from the underlying maternal condition.

There are no reported cases of IV levothyroxine being used to treat myxedema coma in lactating patients; however, because nontreatment is associated with a high probability of significant morbidity or mortality, breastfeeding patients who develop myxedema should be treated with IV levothyroxine.

Geriatric patients should receive lower starting dosages of oral levothyroxine (e.g., 12.5-25 mcg/day); in these patients, the dosage of levothyroxine should be titrated every 6-8 weeks as needed based on serum TSH or free T4 until the patient is euthyroid.

Cautious use (e.g., dosages in the lower end of the recommended range) of IV levothyroxine sodium may be warranted in geriatric patients.

Because of the increased prevalence of cardiovascular disease among elderly patients, oral levothyroxine should be initiated at less than the full replacement dosage in such patients. Use caution when administering IV levothyroxine for myxedema coma in elderly patients and monitor for adverse cardiac effects. Levothyroxine overtreatment can lead to atrial arrhythmias (including atrial fibrillation) in elderly patients.