Levothyroxine Sodium

1 INDICATIONS AND USAGE 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.

2 DOSAGE AND ADMINISTRATION Consider the patient’s age, general physical condition, cardiac risk factors, as well as the 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 ) An initial intravenous loading dose of Levothyroxine Sodium Injection between 300 to 500 mcg followed by once daily intravenous maintenance doses between 50 and 100 mcg should be administered, as clinically indicated, until the patient can tolerate oral therapy. ( 2.1 ) Do not add to other IV fluids. ( 2.2 ) 2.1 Dosage An initial intravenous loading dose of Levothyroxine Sodium Injection between 300 to 500 mcg, followed by once daily intravenous maintenance doses between 50 and 100 mcg, should be administered, as clinically indicated, until the patient can tolerate oral therapy. The age, general physical condition, and cardiac risk factors of the patient, as well as the clinical severity of myxedema and duration of myxedema symptoms should be considered when determining the starting and maintenance dosages of Levothyroxine Sodium Injection. Levothyroxine Sodium Injection produces a gradual increase in the circulating concentrations of the hormone with an approximate half-life of 9 to 10 days in hypothyroid patients. Daily administration of Levothyroxine Sodium Injection should be maintained until the patient is capable of tolerating an oral dose and is clinically stable. For chronic treatment of hypothyroidism, an oral dosage form of levothyroxine should be used to maintain a euthyroid state. Relative bioavailability between Levothyroxine Sodium Injection and oral levothyroxine products has not been established. Based on medical practice, the relative bioavailability between oral and intravenous administration of Levothyroxine Sodium Injection is estimated to be from 48 to 74%. Due to differences in absorption characteristics of patients and the oral levothyroxine product formulations, TSH and thyroid hormone levels should be measured a few weeks after initiating oral levothyroxine and dose adjusted accordingly. 2.2 Dosing in the Elderly and in Patients with Cardiovascular Disease Intravenous levothyroxine may be associated with cardiac toxicity – including arrhythmias, tachycardia, myocardial ischemia and infarction, or worsening of congestive heart failure and death – in the elderly and in those with underlying cardiovascular disease. Therefore, cautious use, including doses in the lower end of the recommended range, may be warranted in these populations. 2.3 Administration Instructions Intravenous levothyroxine may be associated with cardiac toxicity-including arrhythmias, tachycardia, myocardial ischemia and infarction, or worsening of congestive heart failure and death—in the elderly and in those with underlying cardiovascular disease. Therefore, cautious use, including doses in the lower end of the recommended range, may be warranted in these populations. Discard any unused portion. DO NOT ADD LEVOTHYROXINE SODIUM INJECTION TO OTHER INTRAVENOUS FLUIDS. Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.

2.1 Dosage An initial intravenous loading dose of Levothyroxine Sodium Injection between 300 to 500 mcg, followed by once daily intravenous maintenance doses between 50 and 100 mcg, should be administered, as clinically indicated, until the patient can tolerate oral therapy. The age, general physical condition, and cardiac risk factors of the patient, as well as the clinical severity of myxedema and duration of myxedema symptoms should be considered when determining the starting and maintenance dosages of Levothyroxine Sodium Injection. Levothyroxine Sodium Injection produces a gradual increase in the circulating concentrations of the hormone with an approximate …

3 DOSAGE FORMS AND STRENGTHS Levothyroxine Sodium Injection is clear, colorless solution supplied as: • 100 mcg per 5 mL (20 mcg per mL) single-dose vial • 200 mcg per 5 mL (40 mcg per mL) single-dose vial • 500 mcg per 5 mL (100 mcg per mL) single-dose vial Injection: • 100 mcg per 5 mL (20 mcg per mL) single-dose vial • 200 mcg per 5 mL (40 mcg per mL) single-dose vial • 500 mcg per 5 mL (100 mcg per mL) single-dose vial ( 3 )

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

6 ADVERSE REACTIONS 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. 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. 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 Hikma at us.hikma@primevigilance.com or call 1-877-845-0689 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

7 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 Injection. ( 7 , 12.3 ) 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 Nictonic 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 …

8 USE IN SPECIFIC POPULATIONS Elderly and those with underlying cardiovascular disease should receive doses at the lower end of the recommended range. ( 8.5 ) 8.1 Pregnancy Risk Summary The clinical data in pregnant women treated with oral levothyroxine to treat hypothyroidism do not indicate a drug-associated risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes. There are no data available on the use of Levothyroxine Sodium Injection in pregnant women. There are risks to the mother and fetus associated with myxedema coma in pregnancy (see Clinical Considerations) . No developmental or reproductive toxicity studies in animals have been conducted with Levothyroxine Sodium Injection. The estimated background risks of major birth defects and miscarriage for the indicated populations are unknown. All pregnancies have background risks of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risks of major birth defects and miscarriage in clinically recognized pregnancies are 2 to 4% and 15 to 20%, respectively. Clinical Considerations Disease-Associated Maternal and/or Embryo/Fetal Risk Myxedema coma is a medical emergency that can be fatal if left untreated. Delaying treatment in pregnant women with myxedema coma increases the risk of maternal and fetal morbidity and mortality. Life-sustaining therapy for pregnant women with myxedema coma should not be withheld due to potential concerns regarding the effects of Levothyroxine Sodium Injection on the fetus. 8.2 Lactation Risk Summary Published studies report that levothyroxine is present in human milk following the administration of oral levothyroxine. No adverse effects on the breastfed infant have been reported, and there is no information on the effects of levothyroxine on milk production from levothyroxine oral treatment. There are no available data with use of Levothyroxine Sodium Injection in lactating women. The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for Levothyroxine Sodium Injection and any potential adverse effects on the breastfed infant from Levothyroxine Sodium Injection or from the underlying maternal condition. 8.4 Pediatric Use The safety and effectiveness of Levothyroxine Sodium Injection have not been established in pediatric patients. 8.5 Geriatric Use and Patients with Underlying Cardiovascular Disease See Section 2, Dosage and Administration, for full prescribing information in the geriatric patient population. Because of the increased prevalence of cardiovascular disease in the elderly, cautious use of Levothyroxine Sodium Injection in the elderly and in patients with known cardiac risk factors is advised. Atrial fibrillation is a common side effect associated with levothyroxine treatment in the elderly [see Dosage and Administration (2) and Warnings and Precautions (5) ]. 8.6 Renal Impairment Serum creatinine and levothyroxine levels should be closely monitored in patients with severe renal impairment receiving intravenous levothyroxine with betadex sulfobutyl (SBECD) [See Clinical Pharmacology (12.3) ].

8.5 Geriatric Use and Patients with Underlying Cardiovascular Disease See Section 2, Dosage and Administration, for full prescribing information in the geriatric patient population. Because of the increased prevalence of cardiovascular disease in the elderly, cautious use of Levothyroxine Sodium Injection in the elderly and in patients with known cardiac risk factors is advised. Atrial fibrillation is a common side effect associated with levothyroxine treatment in the elderly [see Dosage and Administration (2) and Warnings and Precautions (5) ].

8.6 Renal Impairment Serum creatinine and levothyroxine levels should be closely monitored in patients with severe renal impairment receiving intravenous levothyroxine with betadex sulfobutyl (SBECD) [See Clinical Pharmacology (12.3) ].

12.1 Mechanism of Action Thyroid hormones exert their physiologic actions through control of DNA transcription and protein synthesis. Triiodothyronine (T 3 ) and levothyroxine (T 4 ) diffuse into the cell nucleus and bind to thyroid receptor proteins attached to DNA. This hormone nuclear receptor complex activates gene transcription and synthesis of messenger RNA and cytoplasmic proteins. The physiological actions of thyroid hormones are produced predominantly by T 3 , the majority of which (approximately 80%) is derived from T 4 by deiodination in peripheral tissues.

11 DESCRIPTION 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), 200 mcg per 5 mL (40 mcg per mL), and 500 mcg per 5 mL (100 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

10 OVERDOSAGE In general, the signs and symptoms of overdosage with levothyroxine are those of hyperthyroidism [see Warnings and Precautions (5) and Adverse Reactions (6)]. In addition, confusion and disorientation may occur. Cerebral embolism, shock, coma, and death have been reported. Excessive doses of Levothyroxine Sodium Injection (greater than 500 mcg) are associated with cardiac complications in patients with underlying cardiac disease. Treatment of Overdosage Levothyroxine Sodium Injection should be reduced in dose or temporarily discontinued if signs or symptoms of overdosage occur. To obtain up-to-date information about the treatment of overdose, a good resource is the certified Regional Poison Control Center. In managing overdosage, consider the possibility of multiple drug overdoses, interaction among drugs, and unusual drug kinetics in the patient. In the event of an overdose, appropriate supportive treatment should be initiated as dictated by the patient’s medical status.

16 HOW SUPPLIED/STORAGE AND HANDLING 16.1 How Supplied Levothyroxine Sodium Injection 100 mcg/mL is a clear, colorless to slightly yellow solution, supplied as1 mL per vial. Package of 1 single-dose vial: NDC 24201-002-01 16.2 Storage and Handling Protect from light and store product at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature]. Drug product is preservative free. Discard any unused portion. Manufactured for: Hikma Pharmaceuticals USA Inc. Berkeley Heights, NJ 07922 www.hikma.com/us Revised: 07/2024 462-046-00

16.1 How Supplied Levothyroxine Sodium Injection 100 mcg/mL is a clear, colorless to slightly yellow solution, supplied as1 mL per vial. Package of 1 single-dose vial: NDC 24201-002-01

16.2 Storage and Handling Protect from light and store product at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature]. Drug product is preservative free. Discard any unused portion. Manufactured for: Hikma Pharmaceuticals USA Inc. Berkeley Heights, NJ 07922 www.hikma.com/us Revised: 07/2024 462-046-00