Levothyroxine instructions for administration

Instructions for administration
General principles Hypothyroidism in adults/children in whom growth and puberty are complete''' Pediatric dosage (congenital/acquired hypothyroidism)''' Pregnancy''' Subclinical hypothyroidism''' TSH suppression in well-differentiated thyroid cancer/thyroid nodules''' Myxedema coma'''
 * General principles (pediatrics)
 * Newborns
 * Infants/children

General principles
The goal of replacement therapy is to achieve and maintain a clinical and biochemical euthyroid state. The goal of suppressive therapy is to inhibit growth and/or function of abnormal thyroid tissue. The dose of Levothyroxine sodium tablets that is adequate to achieve these goals depends on a variety of factors including the patient's age, body weight, cardiovascular status, concomitant medical conditions, including pregnancy, concomitant medications, and the specific nature of the condition being treated. Hence, the following recommendations serve only as dosing guidelines. Dosing must be individualized and adjustments made based on periodic assessment of the patient's clinical response and laboratory parameters. Levothyroxine sodium tablets should be taken in the morning on an empty stomach, at least one-half hour before any food is eaten. Levothyroxine sodium tablets should be taken at least 4 hours apart from drugs that are known to interfere with its absorption. Due to the long half-life of Levothyroxine, the peak therapeutic effect at a given dose of Levothyroxine sodium may not be attained for 4 to 6 weeks. Caution should be exercised when administering Levothyroxine sodium tablets to patients with underlying cardiovascular disease, to the elderly, and to those with concomitant adrenal insufficiency. Return to top

Hypothyroidism in adults/children in whom growth and puberty are complete
Therapy may begin at full replacement doses in otherwise healthy individuals less than 50 years old and in those older than 50 years who have been recently treated for hyperthyroidism or who have been hypothyroid for only a short time (such as a few months). The average full replacement dose of Levothyroxine sodium is approximately 1.7 mcg/kg/day (e.g., 100 to 125 mcg/day for a 70 kg adult). Older patients may require less than 1 mcg/kg/day. Levothyroxine sodium doses greater than 200 mcg/day are seldom required. An inadequate response to daily doses ≥ 300 mcg/day is rare and may indicate poor compliance, malabsorption, and/or drug interactions. For most patients older than 50 years or for patients under 50 years of age with underlying cardiac disease, an initial starting dose of 25 to 50 mcg/day of Levothyroxine sodium is recommended, with gradual increments in dose at 6 to 8 week intervals, as needed. The recommended starting dose of Levothyroxine sodium in elderly patients with cardiac disease is 12.5 to 25 mcg/day, with gradual dose increments at 4 to 6 week intervals. The Levothyroxine sodium dose is generally adjusted in 12.5 to 25 mcg increments until the patient with primary hypothyroidism is clinically euthyroid and the serum TSH has normalized. In patients with severe hypothyroidism, the recommended initial Levothyroxine sodium dose is 12.5 to 25 mcg/day with increases of 25 mcg/day every 2 to 4 weeks, accompanied by clinical and laboratory assessment, until the TSH level is normalized. In patients with secondary (pituitary) or tertiary (hypothalamic) hypothyroidism, the Levothyroxine sodium dose should be titrated until the patient is clinically euthyroid and the serum free-T4 level is restored to the upper half of the normal range. Return to top

Pediatric dosage (congenital/acquired hypothyroidism)
Because of the danger of withdrawal, abrupt discontinuation of treatment should be avoided. Return to top

General principles (pediatrics)
In general, Levothyroxine therapy should be instituted at full replacement doses as soon as possible. Delays in diagnosis and institution of therapy may have deleterious effects on the child's intellectual and physical growth and development. Undertreatment and overtreatment should be avoided. Levothyroxine sodium tablets may be administered to infants and children who cannot swallow intact tablets by crushing the tablet and suspending the freshly crushed tablet in a small amount (5 to 10 mL or 1 to 2 teaspoons) of water. This suspension can be administered by spoon or by dropper. DO NOT STORE THE SUSPENSION. Foods that decrease absorption of Levothyroxine, such as soybean infant formula, should not be used for administering Levothyroxine sodium tablets. Return to top

Newborns
The recommended starting dose of Levothyroxine sodium in newborn infants is 10 to 15 mcg/kg/day. A lower starting dose (e.g., 25 mcg/day) should be considered in infants at risk for cardiac failure, and the dose should be increased in 4 to 6 weeks as needed based on clinical and laboratory response to treatment. In infants with very low (< 5 mcg/dL) or undetectable serum T4 concentrations, the recommended initial starting dose is 50 mcg/day of Levothyroxine sodium. Return to top

Infants/children
Levothyroxine therapy is usually initiated at full replacement doses, with the recommended dose per body weight decreasing with age (see table below). However, in children with chronic or severe hypothyroidism, an initial dose of 25 mcg/day of Levothyroxine sodium is recommended with increments of 25 mcg every 2 to 4 weeks until the desired effect is achieved. Hyperactivity in an older child can be minimized if the starting dose is one-fourth of the recommended full replacement dose, and the dose is then increased on a weekly basis by an amount equal to one-fourth the full-recommended replacement dose until the full recommended replacement dose is reached. Table: Levothyroxine Sodium Dosing Guidelines for Pediatric Hypothyroidism Return to top
 * The dose should be adjusted based on clinical response and laboratory parameters.

Pregnancy
Pregnancy may increase Levothyroxine requirements. Return to top

Subclinical hypothyroidism
If this condition is treated, a lower Levothyroxine sodium dose (e.g., 1 mcg/kg/day) than that used for full replacement may be adequate to normalize the serum TSH level. Patients who are not treated should be monitored yearly for changes in clinical status and thyroid laboratory parameters. Return to top

TSH suppression in well-differentiated thyroid cancer/thyroid nodules
The target level for TSH suppression in these conditions has not been established with controlled studies. In addition, the efficacy of TSH suppression for benign nodular disease is controversial. Therefore, the dose of Levothyroxine sodium tablets used for TSH suppression should be individualized based on the specific disease and the patient being treated. In the treatment of well-differentiated (papillary and follicular) thyroid cancer, Levothyroxine is used as an adjunct to surgery and radioiodine therapy. Generally, TSH is suppressed to <0.1 mU/L, and this usually requires a Levothyroxine sodium dose of greater than 2 mcg/kg/day. However, in patients with high-risk tumors, the target level for TSH suppression may be <0.01 mU/L. In the treatment of benign nodules and nontoxic multinodular goiter, TSH is generally suppressed to a higher target (e.g., 0.1 to 0.5 mU/L for nodules and 0.5 to 1.0 mU/L for multinodular goiter) than that used for the treatment of thyroid cancer. Levothyroxine sodium is contraindicated if the serum TSH is already suppressed due to the risk of precipitating overt thyrotoxicosis. Return to top

Myxedema coma
Myxedema coma is a life-threatening emergency characterized by poor circulation and hypometabolism, and may result in unpredictable absorption of Levothyroxine sodium from the gastrointestinal tract. Therefore, oral thyroid hormone drug products are not recommended to treat this condition. Thyroid hormone products formulated for intravenous administration should be administered. Return to top