LEVOTHYROXINE SODIUM- levothyroxine sodium_tablet

CLINICAL PHARMACOLOGY
Thyroid hormone synthesis and secretion is regulated by the hypothalamic-pituitary-thyroid axis. Thyrotropin-releasing hormone (TRH) released from the hypothalamus stimulates secretion of thyrotropin-stimulating hormone, TSH, from the anterior pituitary. TSH, in turn, is the physiologic stimulus for the synthesis and secretion of thyroid hormones, L-thyroxine (T 4 3 3 4 3 4 The mechanisms by which thyroid hormones exert their physiologic actions are not completely understood, but it is thought that their principal effects are exerted through control of DNA transcription and protein synthesis. T 3 4 Thyroid hormones regulate multiple metabolic processes and play an essential role in normal growth and development, and normal maturation of the central nervous system and bone. The metabolic actions of thyroid hormones include augmentation of cellular respiration and thermogenesis, as well as metabolism of proteins, carbohydrates and lipids. The protein anabolic effects of thyroid hormones are essential to normal growth and development. The physiologic actions of thyroid hormones are produced predominately by T 3 4 Levothyroxine, at doses individualized according to patient response, is effective as replacement or supplemental therapy in hypothyroidism of any etiology, except transient hypothyroidism during the recovery phase of subacute thyroiditis. Levothyroxine is also effective in the suppression of pituitary TSH secretion in the treatment or prevention of various types of euthyroid goiters, including thyroid nodules, Hashimoto''s thyroiditis, multinodular goiter and, as adjunctive therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer (see INDICATIONS AND USAGE PRECAUTIONS DOSAGE AND ADMINISTRATION Absorption 4 4 4 4 PRECAUTIONS, Drug Interactions Error! Hyperlink reference not valid. Distribution 4 4 3 PRECAUTIONS, Drug Interactions Error! Hyperlink reference not valid. PRECAUTIONS, Pregnancy Metabolism 4 TABLE 1 3 4 4 3 4 4 3 3 3 3 3 Elimination 4 4 Table 1: Pharmacokinetic Parameters of Thyroid Hormones in Euthyroid Patients 1 2 Hormone Ratio in Biologic t 1/2 Protein 2 Levothyroxine (T 4 10 - 20 1 6-7 1 99. 96 Liothyronine (T 3 1 4 <= 2 99.
Pharmacokinetics
Absorption 4 4 4 4 PRECAUTIONS, Drug Interactions Error! Hyperlink reference not valid. Distribution 4 4 3 PRECAUTIONS, Drug Interactions Error! Hyperlink reference not valid. PRECAUTIONS, Pregnancy Metabolism 4 TABLE 1 3 4 4 3 4 4 3 3 3 3 3 Elimination 4 4 Table 1: Pharmacokinetic Parameters of Thyroid Hormones in Euthyroid Patients 1 2 Hormone Ratio in Biologic t 1/2 Protein 2 Levothyroxine (T 4 10 - 20 1 6-7 1 99.96 Liothyronine (T 3 1 4 <= 2 99.5

Excipients: Colloidal silicon dioxide, lactose, magnesium stearate, microcrystalline cellulose, corn starch, acacia and sodium starch glycolate. The following are the coloring additives per tablet strength: Strength (mcg) Color Additive(s) 25 FD&C Yellow No. 6 Aluminum Lake 50 None 75 FD&C Red No. 40 Aluminum Lake, FD&C Blue No. 2 Aluminum Lake 88 D&C Yellow No. 10 Aluminum Lake, FD&C Yellow No. 6 Aluminum Lake, FD&C Blue No. 1 Aluminum Lake 100 D&C Yellow No. 10 Aluminum Lake, FD&C Yellow No. 6 Aluminum Lake 112 D&C Red No. 27 Aluminum Lake 125 FD&C Yellow No. 6 Aluminum Lake, FD&C Red No. 40 Aluminum Lake, FD&C Blue No. 1 Aluminum Lake 137 FD&C Blue No. 1 Aluminum Lake 150 FD&C Blue No. 2 Aluminum Lake 175 FD&C Blue No. 1 Aluminum Lake, D&C Red No. 27 Aluminum Lake 200 FD&C Red No. 40 Aluminum Lake 300 D&C Yellow No. 10 Aluminum Lake, FD&C Yellow No. 6 Aluminum Lake, FD&C Blue No. 1 Aluminum Lake

Levothyroxine sodium is used for the following indications: Hypothyroidism Pituitary TSH Suppression WARNINGS PRECAUTIONS WARNINGS PRECAUTIONS WARNINGS PRECAUTIONS

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, USP 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 (see WARNINGS PRECAUTIONS PRECAUTIONS, Laboratory Tests Levothyroxine Sodium Tablets, USP should be taken in the morning on an empty stomach, at least one-half hour to one hour before any food is eaten. Levothyroxine Sodium Tablets, USP should be taken at least 4 hours apart from drugs that are known to interfere with its absorption (see PRECAUTIONS, Drug Interactions Due to the long half-life of levothyroxine, the peak therapeutic effect at a given dose of levothyroxine sodium may not be attained for 4-6 weeks. Caution should be exercised when administering Levothyroxine Sodium Tablets, USP to patients with underlying cardiovascular disease, to the elderly, and to those with concomitant adrenal insufficiency (see PRECAUTIONS Specific Patient Populations: Hypothyroidism in Adults and in Children in Whom Growth and Puberty are Complete WARNINGS PRECAUTIONS, Laboratory Tests 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., 100-125 mcg/day For most patients older than 50 years or for patients under 50 years of age with underlying cardiac disease, an initial starting dose of 25-50 mcg/day 12.5-25 mcg/day In patients with severe hypothyroidism, the recommended initial levothyroxine sodium dose is 12.5-25 mcg/day 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-T 4 Pediatric Dosage - Congenital or Acquired Hypothyroidism PRECAUTIONS, Laboratory Tests General Principles 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 (see PRECAUTIONS, Pediatric Use Levothyroxine Sodium Tablets, USP 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 (5-10 mL or 1-2 teaspoons) of water. This suspension can be administered by spoon or dropper. DO NOT STORE THE SUSPENSION. PRECAUTIONS, Drug-Food Interactions Newborns The recommended starting dose of levothyroxine sodium in newborn infants is 10-15 mcg/kg/day 4 50 mcg/day Infants and Children Levothyroxine therapy is usually initiated at full replacement doses, with the recommended dose per body weight decreasing with age (see TABLE 3 25 mcg/day 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 3: Levothyroxine Sodium Dosing Guidelines for Pediatric Hypothyroidism a. The dose should be adjusted based on clinical response and laboratory parameters (see PRECAUTlONS, Laboratory Tests Pediatric Use AGE Daily Dose Per Kg Body Weight a 0-3 months 10-15 mcg/kg/day 3-6 months 8-10 mcg/kg/day 6-12 months 6-8 mcg/kg/day 1-5 years 5-6 mcg/kg/day 6-12 years 4-5 mcg/kg/day >12 years but growth and puberty incomplete 2-3 mcg/kg/day Growth and puberty complete 1.7 mcg/kg/day Pregnancy- PREGNANCY Subclinical Hypothyroidism- 1 mcg/kg/day TSH Suppression in Well-differentiated Thyroid Cancer and Thyroid Nodules- 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 In the treatment of benign nodules and nontoxic multinodular goiter, TSH is generally suppressed to a higher target (e.g., 0.1-0.5 mU/L for nodules and 0.5-1.0 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 (see CONTRAINDICATIONS WARNINGS PRECAUTIONS Myxedema Coma

Adverse reactions associated with levothyroxine therapy are primarily those of hyperthyroidism due to therapeutic overdosage (see PRECAUTIONS OVERDOSAGE General: Central nervous system: Musculoskeletal: Cardiovascular: Respiratory: Gastrointestinal: Dermatologic: Endocrine: Reproductive: Pseudotumor cerebri and slipped capital femoral epiphysis have been reported in children receiving levothyroxine therapy. Overtreatment may result in craniosynostosis in infants and premature closure of the epiphyses in children with resultant compromised height. Seizures have been reported rarely with the institution of levothyroxine therapy. Inadequate levothyroxine dosage will produce or fail to ameliorate the signs and symptoms of hypothyroidism. Hypersensitivity reactions to inactive ingredients have occurred in patients treated with thyroid hormone products. These include urticaria, pruritus, skin rash, flushing, angioedema, various Gl symptoms (abdominal pain, nausea, vomiting and diarrhea), fever, arthralgia, serum sickness and wheezing. Hypersensitivity to levothyroxine itself is not known to occur.

Levothyroxine is contraindicated in patients with untreated subclinical (suppressed serum TSH level with normal T 3 4 PRECAUTIONS DESCRIPTION, Inactive Ingredients

Pregnancy - Category A
Studies in women taking levothyroxine sodium during pregnancy have not shown an increased risk of congenital abnormalities. Therefore, the possibility of fetal harm appears remote. Levothyroxine Sodium Tablets, USP should not be discontinued during pregnancy and hypothyroidism diagnosed during pregnancy should be promptly treated. Hypothyroidism during pregnancy is associated with a higher rate of complications, including spontaneous abortion, pre-eclampsia, stillbirth and premature delivery. Maternal hypothyroidism may have an adverse effect on fetal and childhood growth and development. During pregnancy, serum T 4 Thyroid hormones cross the placental barrier to some extent as evidenced by levels in cord blood of athyroceotic fetuses being approximately one third maternal levels. Transfer of thyroid hormone from the mother to the fetus, however, may not be adequate to prevent in utero,
Nursing Mothers
Although thyroid hormones are excreted only minimally in human milk, caution should be exercised when Levothyroxine Sodium Tablets, USP is administered to a nursing woman. However, adequate replacement doses of levothyroxine are generally needed to maintain normal lactation.
Pediatric Use
General The goal of treatment in pediatric patients with hypothyroidism is to achieve and maintain normal intellectual and physical growth and development. The initial dose of levothyroxine varies with age and body weight (see DOSAGE AND ADMINISTRATION Table 3 PRECAUTIONS, Laboratory Tests In children in whom a diagnosis of permanent hypothyroidism has not been established, it is recommended that levothyroxine administration be discontinued for a 30-day trial period, but only after the child is at least 3 years of age. Serum T 4 4 4 Since some more severely affected children may become clinically hypothyroid when treatment is discontinued for 30 days, an alternate approach is to reduce the replacement dose of levothyroxine by half during the 30-day trial period. If, after 30 days, the serum TSH is elevated above 20 mU/L, the diagnosis of permanent hypothyroidism is confirmed, and full replacement therapy should be resumed. However, if the serum TSH has not risen to greater than 20 mU/L, levothyroxine treatment should be discontinued for another 30-day trial period followed by repeat serum T 4 The presence of concomitant medical conditions should be considered in certain clinical circumstances and, if present, appropriately treated (see PRECAUTIONS Congenital Hypothyroidism PRECAUTIONS, Laboratory Tests DOSAGE AND ADMINISTRATION Rapid restoration of normal serum T 4 During the first 2 weeks of Levothyroxine Sodium Tablets, USP therapy, infants should be closely monitored for cardiac overload, arrhythmias, and aspiration from avid suckling. The patient should be monitored closely to avoid undertreatment or overtreatment. Undertreatment may have deleterious effects on intellectual development and linear growth. Overtreatment has been associated with craniosynostosis in infants, and may adversely affect the tempo of brain maturation and accelerate the bone age with resultant premature closure of the epiphyses and compromised adult stature. Acquired Hypothyroidism in Pediatric Patients The patient should be monitored closely to avoid undertreatment and overtreatment. Undertreatment may result in poor school performance due to impaired concentration and slowed mentation and in reduced adult height. Overtreatment may accelerate the bone age and result in premature epiphyseal closure and compromised adult stature. Treated children may manifest a period of catch-up growth, which may be adequate in some cases to normalize adult height. In children with severe or prolonged hypothyroidism, catch-up growth may not be adequate to normalize adult height.
Geriatric Use
Because of the increased prevalence of cardiovascular disease among the elderly, levothyroxine therapy should not be initiated at the full replacement dose (see WARNINGS PRECAUTIONS DOSAGE AND ADMINISTRATION

Drug Interactions
Many drugs affect thyroid hormone pharmacokinetics and metabolism (e.g., absorption, synthesis, secretion, catabolism, protein binding, and target tissue response) and may alter the therapeutic response to Levothyroxine Sodium Tablets, USP. In addition, thyroid hormones and thyroid status have varied effects on the pharmacokinetics and action of other drugs. A listing of drug-thyroidal axis interactions is contained in Table 2. The list of drug-thyroidal axis interactions in Table 2 may not be comprehensive due to the introduction of new drugs that interact with the thyroidal axis or the discovery of previously unknown interactions. The prescriber should be aware of this fact and should consult appropriate reference sources (e.g., package inserts of newly approved drugs, medical literature) for additional information if a drug-drug interaction with levothyroxine is suspected. Table 2: Drug-Thyroidal Axis Interactions Drug or Drug Class Effect Drugs that may reduce TSH secretion - the reduction is not sustained; therefore, hypothyroidism does not occur Dopamine/Dopamine Agonists Use of these agents may result in a transient reduction in TSH secretion when administered at the following doses: dopamine ( >= 1 mcg/kg/min); Glucocorticoids (hydrocortisone >= 100 mg/day or equivalent); Octreotide ( > 100 mcg/day). Drugs that alter thyroid hormone secretion Drugs that may decrease thyroid hormone secretion, which may result in hypothyroidism Aminoglutethimide Long-term lithium therapy can result in goiter in up to 50% of patients, and either subclinical or overt hypothyroidism, each in up to 20% of patients. The fetus, neonate, elderly and euthyroid patients with underlying thyroid disease (e.g., Hashimoto''s thyroiditis or with Grave''s disease previously treated with radioiodine or surgery) are among those individuals who are particularly susceptible to iodine-induced hypothyroidism. Oral cholecystographic agents and amiodarone are slowly excreted, producing more prolonged hypothyroidism than parenterally administered iodinated contrast agents. Long-term amino-glu-tethimide therapy may minimally decrease T 4 3 Drugs that may increase thyroid hormone secretion, which may result in hyperthyroidism Amiodarone Iodide and drugs that contain pharmacologic amounts of iodide may cause hyperthyroidism in euthyroid patients with Grave''s disease previously treated with antithyroid drugs or in euthyroid patients with thyroid autonomy (e.g., multinodular goiter or hyper functioning thyroid adenoma). Hyperthyroidism may develop over several weeks and may persist for several months after therapy discontinuation. Amiodarone may induce hyperthyroidism by causing thyroiditis. Drugs that may decrease T 4 absorption, which may result in hypothyroidism Antacids Concurrent use may reduce the efficacy of levothyroxine by binding and delaying or preventing absorption, potentially resulting in hypothyroidism. Calcium carbonate may form an insoluble chelate with levothyroxine, and ferrous sulfate likely forms a ferric-thyroxine complex. Administer levothyroxine at least 4 hours apart from these agents. Patients treated concomitantly with orlistat and levothyroxine should be monitored for changes in thyroid function. Drugs that may alter T 4 and T 3 serum transport - but FT 4 concentration remains normal; and, therefore, the patient remains euthyroid Drugs that may increase serum TBG concentration Drugs that may decrease serum TBG concentration Clofibrate Androgens / Anabolic Steroids Drugs that may cause protein-binding site displacement Furosemide ( > 80 mg IV) Administration of these agents with levothyroxine results in an initial transient increase in FT 4 4 4 4 3 4 4 4 Drugs that may alter T 4 and T 3 metabolism Drugs that may increase hepatic metabolism, which may result in hypothyroidism Carbamazepine Stimulation of hepatic microsomal drug-metabolizing enzyme activity may cause increased hepatic degradation of levothyroxine, resulting in increased Ievothyroxine requirements. Phenytoin and carbamazepine reduce serum protein binding of levothyroxine, and total- and free-T 4 Drugs that may decrease T 4 5'' - deiodinase activity Amiodarone Administration of these enzyme inhibitors decrease the peripheral conversion of T 4 3 3 4 3 4 3 4 3 4 Miscellaneous Anticoagulants (oral) Thyroid hormones appear to increase the catabolism of vitamin K-dependent clotting factors, thereby increasing the anticoagulant activity of oral anticoagulants. Concomitant use of these agents impairs the compensatory increases in clotting factor synthesis. Prothrombin time should be carefully monitored in patients taking levothyroxine and oral anticoagulants and the dose of anticoagulant therapy adjusted accordingly. Antidepressants Concurrent use of tri/tetracyclic antidepressants and levothyroxine may increase the therapeutic and toxic effects of both drugs, possibly due to increased receptor sensitivity to catecholamines.Toxic effects may include increased risk of cardiac arrhythmias and CNS stimulation; onset of action of tricyclics may be accelerated. Administration of sertraline in patients stabilized on levothyroxine may result in increased levothyroxine requirements. Antidiabetic Agents Addition of levothyroxine to antidiabetic or insulin therapy may result in increased antidiabetic agent or insulin requirements. Careful monitoring of diabetic control is recommended, especially when thyroid therapy is started, changed, or discontinued. Cardiac Glycosides Serum digitalis glycoside levels may be reduced in hyperthyroidism or when the hypothyroid patient is converted to the euthyroid state. Therapeutic effect of digitalis glycosides may be reduced. Cytokines Therapy with interferon-alpha has been associated with the development of antithyroid microsomal antibodies in 20% of patients and some have transient hypothyroidism, hyperthyroidism, or both. Patients who have antithyroid antibodies before treatment are at higher risk for thyroid dysfunction during treatment. Interleukin-2 has been associated with transient painless thyroiditis in 20% of patients. Interferon-beta and -gamma have not been reported to cause thyroid dysfunction. Growth Hormones Excessive use of thyroid hormones with growth hormones may accelerate epiphyseal closure. However, untreated hypothyroidism may interfere with growth response to growth hormone. Ketamine Concurrent use may produce marked hypertension and tachycardia; cautious administration to patients receiving thyroid hormone therapy is recommended. Methylxanthine Bronchodilators Decreased theophylline clearance may occur in hypothyroid patients; clearance returns to normal when the euthyroid state is achieved. Radiographic Agents Thyroid hormones may reduce the uptake of 123 131 99m Sympathomimetics Concurrent use may increase the effects of sympathomimetics or thyroid hormone. Thyroid hormones may increase the risk of coronary insufficiency when sympathomimetic agents are administered to patients with coronary artery disease. Chloral Hydrate These agents have been associated with thyroid hormone and/or TSH level alterations by various mechanisms. Oral anticoagulants Table 2 Digitalis glycosides Table 2
Drug-Food Interactions
Consumption of certain foods may affect levothyroxine absorption thereby necessitating adjustments in dosing. Soybean flour (infant formula), cotton seed meal, walnuts, and dietary fiber may bind and decrease the absorption of levothyroxine sodium from the GI tract.
Drug-Laboratory Test Interactions
Changes in TBG concentration must be considered when interpreting T 4 3 4 4 Table 2

WARNINGS
WARNING: Thyroid hormones, including Levothyroxine Sodium Tablets, USP, either alone or with other therapeutic agents, should not be used for the treatment of obesity for weight loss. In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction. Larger doses may produce serious or even life threatening manifestations of toxicity, particularly when given in association with sympathomimetic amines such as those used for their anorectic effects. Levothyroxine sodium should not be used in the treatment of male or female infertility unless this condition is associated with hypothyroidism. In patients with nontoxic diffuse goiter or nodular thyroid disease, particularly the elderly or those with underlying cardiovascular disease, levothyroxine sodium therapy is contraindicated if the serum TSH level is already suppressed due to the risk of precipitating overt thyrotoxicosis (see CONTRAINDICATIONS.
Carcinogenesis,Mutagenesis, and Impairment of Fertility
Animal studies have not been performed to evaluate the carcinogenic potential, mutagenic potential or effects on fertility of levothyroxine. The synthetic T 4
OVERDOSAGE
The signs and symptoms of overdosage are those of hyperthyroidism (see PRECAUTIONS ADVERSE REACTIONS Treatment of Overdosage Levothyroxine sodium should be reduced in dose or temporarily discontinued if signs or symptoms of overdosage occur. Acute Massive Overdosage 4 3 4

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