LEVOTHYROXINE SODIUM

Levothyroxine Sodium Injection contains synthetic crystalline levothyroxine (T4) in sodium salt form. Levothyroxine sodium has an empirical formula of C 15 H 10 I 4 NNaO 4 , a molecular weight of 798.85 g/mol (anhydrous), and the following structural formula: Levothyroxine Sodium Injection is a sterile, preservative free, clear, colorless, sterile solution for intravenous administration available as: 100 mcg per 5 mL (20 mcg per mL). Each mL of Levothyroxine Sodium Injection also contains 10 mg Tromethamine, USP; 0.14 mg Sodium Iodide, USP; 6.48 mg Sodium Chloride, USP; and Water for Injection, USP Sodium hydroxide, NF and/or Hydrochloric acid, USP may have been added for pH adjustment (9.5 – 10.8). Levothyroxine Sodium Injection is in single dose clear glass vials. Structural Formula

Levothyroxine Sodium Injection is indicated for the treatment of myxedema coma. Levothyroxine Sodium Injection is L-thyroxine (T4) indicated in adult patients for the treatment of myxedema coma. ( 1 ) Limitations of Use: Not recommended as a substitute for oral levothyroxine sodium because the relative bioavailability of Levothyroxine Sodium Injection to oral levothyroxine sodium has not been established and there is a risk of inaccurate dose conversion. ( 1 ) Limitations of Use: Not recommended as a substitute for oral levothyroxine sodium because the relative bioavailability of Levothyroxine Sodium Injection to oral levothyroxine sodium has not been established and there is a risk of inaccurate dose conversion.

Consider the age, general physical condition, cardiac risk factors, and clinical severity of myxedema and duration of myxedema symptoms when determining dosages of Levothyroxine Sodium Injection. ( 2.1 ) Start with lower doses in elderly patients and in patients with underlying cardiovascular disease. ( 2.1 ) The recommended loading dose is 300 mcg to 500 mcg administered intravenously. ( 2.1 ) The recommended maintenance dose is 50 mcg to 100 mcg administered intravenously daily until the patient can tolerate oral therapy. ( 2.1 ) Administer Levothyroxine Sodium Injection intravenously at a rate not to exceed 100 mcg per minute. ( 2.2 ) Do not add Levothyroxine Sodium Injection to intravenous fluids. ( 2.2 ) 2.1 Dosage Consider the age, general physical condition, cardiac risk factors, and clinical severity of myxedema and duration of myxedema symptoms when determining the starting and maintenance dosages of Levothyroxine Sodium Injection. Start with lower doses in elderly patients and in patients with underlying cardiovascular disease [see Warnings and Precautions ( 5.1 ) and Use in Specific Populations ( 8.5 )]. The recommended loading dose of Levothyroxine Sodium Injection is 300 mcg to 500 mcg administered intravenously. The recommended maintenance dose of Levothyroxine Sodium Injection is 50 mcg to 100 mcg administered intravenously daily until the patient can tolerate oral therapy. 2.2 Administration Instructions Administer Levothyroxine Sodium Injection as an intravenous injection at a rate not to exceed 100 mcg per minute. Do not add Levothyroxine Sodium Injection to intravenous fluids. Inspect Levothyroxine Sodium Injection visually prior to injection. It should appear clear and colorless, solution free of visible particulates. Do not use if particulate matter or coloration is seen. Discard any unused portion.

Uncorrected adrenal insufficiency [see Warnings and Precautions ( 5.2 )] Uncorrected adrenal insufficiency. ( 4 )

Adverse reactions associated with levothyroxine are primarily those of hyperthyroidism due to therapeutic overdosage [see Warnings and Precautions ( 5 ) , Overdosage ( 10 ) ] . They include the following: General: fatigue, increased appetite, weight loss, heat intolerance, fever, excessive sweating Central nervous system: headache, hyperactivity, nervousness, anxiety, irritability, emotional lability, insomnia Musculoskeletal: tremors, muscle weakness, muscle spasm Cardiovascular: palpitations, tachycardia, arrhythmias, increased pulse and blood pressure, heart failure, angina, myocardial infarction, cardiac arrest Respiratory: dyspnea Gastrointestinal: diarrhea, vomiting, abdominal cramps, elevations in liver function tests Dermatologic: flushing, rash Seizures have been reported rarely with the institution of levothyroxine therapy. Adverse reactions associated with Levothyroxine Sodium Injection are primarily those of hyperthyroidism due to therapeutic overdosage: 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. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Fresenius Kabi USA, LLC at 1-800-551-7176 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. Hypersensitivity Reactions Hypersensitivity reactions to inactive ingredients have occurred in patients treated with thyroid hormone products. These include urticaria, pruritus, skin rash, flushing, angioedema, various gastrointestinal symptoms (abdominal pain, nausea, vomiting and diarrhea), fever, arthralgia, serum sickness, and wheezing. Hypersensitivity to levothyroxine itself is not known to occur.

See full prescribing information for drugs that affect thyroid hormone pharmacokinetics and metabolism (e.g., synthesis, secretion, catabolism, protein binding, and target tissue response) that may alter the therapeutic response to Levothyroxine Sodium Injection. ( 7 ) 7.1 Drugs Known to Affect Thyroid Hormone Pharmacokinetics Many drugs affect thyroid hormone pharmacokinetics and metabolism (e.g., synthesis, secretion, catabolism, protein binding, and target tissue response) and may alter the therapeutic response to Levothyroxine Sodium Injection (see Tables 1 - 3 ). Table 1: Drugs That May Alter T 4 and Triiodothyronine (T 3 ) Serum Transport Without Effecting Free Thyroxine (FT 4 ) Concentration (Euthyroidism) Drug or Drug Class Effect Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin / Methadone 5-Fluorouracil Mitotane Tamoxifen These drugs may increase serum thyroxine-binding globulin (TBG) concentration. Androgens / Anabolic Steroids Asparaginase Glucocorticoids Slow-Release Nicotinic Acid These drugs may decrease serum TBG concentration. Potential impact (below): Administration of these agents with levothyroxine results in an initial transient increase in FT 4 . Continued administration results in a decrease in serum T 4 and normal FT 4 and TSH concentrations. Salicylates (> 2 g/day) Salicylates inhibit binding of T 4 and T 3 to TBG and transthyretin. An initial increase in serum FT 4 is followed by return of FT 4 to normal levels with sustained therapeutic serum salicylate concentrations, although total T 4 levels may decrease by as much as 30%. Other drugs: Carbamazepine Furosemide (> 80 mg IV) Heparin Hydantoins Non-Steroidal Anti-inflammatory Drugs - Fenamates These drugs may cause protein-binding site displacement. Furosemide has been shown to inhibit the protein binding of T4 to TBG and albumin, causing an increase free T4 fraction in serum. Furosemide competes for T4-binding sites on TBG, prealbumin, and albumin, so that a single high dose can acutely lower the total T4 level. Phenytoin and carbamazepine reduce serum protein binding of levothyroxine, and total and free T4 may be reduced by 20% to 40%, but most patients have normal serum TSH levels and are clinically euthyroid. Closely monitor thyroid hormone parameters. Table 2: Drugs That May Alter Hepatic Metabolism of T 4 (Hypothyroidism) Potential impact: Stimulation of hepatic microsomal drug-metabolizing enzyme activity may cause increased hepatic degradation of levothyroxine, resulting in increased levothyroxine requirements. Drug or Drug Class Effect Phenobarbital Rifampin Phenobarbital has been shown to reduce the response to thyroxine. Phenobarbital increases L-thyroxine metabolism by inducing uridine 5'-diphospho-glucuronosyltransferase (UGT) and leads to a lower T4 serum levels. Changes in thyroid status may occur if barbiturates are added or withdrawn from patients being treated for hypothyroidism. Rifampin has been shown to accelerate the metabolism of levothyroxine. Table 3: Drugs That May Decrease Conversion of T 4 to T 3 Potential impact: Administration of these enzyme inhibitors decreases the peripheral conversion of T 4 to T 3 , leading to decreased T 3 levels. However, serum T 4 levels are usually normal but may occasionally be slightly increased. Drug or Drug Class Effect Beta-adrenergic antagonists (e.g., Propranolol > 160 mg/day) In patients treated with large doses of propranolol (> 160 mg/day), T 3 and T 4 levels change slightly, TSH levels remain normal, and patients are clinically euthyroid. It should be noted that actions of particular beta-adrenergic antagonists may be impaired when the hypothyroid patient is converted to the euthyroid state. Glucocorticoids (e.g., Dexamethasone ≥ 4 mg/day) Short-term administration of large doses of glucocorticoids may decrease serum T 3 concentrations by 30% with minimal change in serum T 4 levels. However, long-term glucocorticoid therapy may result in slightly decreased T 3 and T 4 levels due to decreased TBG production (See above). Other drugs: Amiodarone Amiodarone inhibits peripheral conversion of levothyroxine (T4) to triiodothyronine (T3) and may cause isolated biochemical changes (increase in serum free-T4, and decreased or normal free-T3) in clinically euthyroid patients. 7.2 Antidiabetic Therapy Addition of levothyroxine to antidiabetic or insulin therapy may result in increased antidiabetic agent or insulin requirements. Careful monitoring of glycemic control is recommended. 7.3 Oral Anticoagulants Levothyroxine increases the response to oral anticoagulant therapy. Therefore, a decrease in the dose of anticoagulant may be warranted with correction of the hypothyroid state. Closely monitor coagulation tests to permit appropriate and timely dosage adjustments. 7.4 Digitalis Glycosides Levothyroxine may reduce the therapeutic effects of digitalis glycosides. Serum digitalis glycoside levels may be decreased when a hypothyroid patient becomes euthyroid, necessitating an increase in the dose of digitalis glycosides. 7.5 Antidepressant Therapy Concurrent use of tricyclic (e.g., amitriptyline) or tetracyclic (e.g., maprotiline) 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 central nervous system stimulation. Levothyroxine may accelerate the onset of action of tricyclics. Administration of sertraline in patients stabilized on levothyroxine may result in increased levothyroxine requirements. 7.6 Ketamine Concurrent use of ketamine and levothyroxine may produce marked hypertension and tachycardia. Closely monitor blood pressure and heart rate in these patients. 7.7 Sympathomimetics Concurrent use may of sympathomimetics and levothyroxine 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. 7.8 Drug-Laboratory Test Interactions Consider changes in TBG concentration when interpreting T4 and T3 values. Measure and evaluate unbound (free) hormone and/or determine the free T4 index (FT4I) in this circumstance. Pregnancy, infectious hepatitis, estrogens, estrogen containing oral contraceptives, and acute intermittent porphyria increase TBG concentrations. Nephrosis, severe hypoproteinemia, severe liver disease, acromegaly, androgens, and corticosteroids decrease TBG concentration. Familial hyper- or hypo-thyroxine binding globulinemias have been described, with the incidence of TBG deficiency approximating 1 in 9,000.