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Levothyroxine Sodium (Tablet)

Source:http://www4.wiwiss.fu-berlin.de/dailymed/resource/drugs/896

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Levothyroxine Sodium (Tablet)
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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 .<br/>Specific Patient Populations:<br/>Hypothyroidism in Adults and in 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 isgenerally 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-Tlevel is restored to the upper half of the normal range.<br/>Pediatric Dosage - Congenital or Acquired Hypothyroidism:<br/>Pregnancy: Pregnancy may increase levothyroxine requirements .<br/>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.<br/>TSH Suppression in Well-differentiated Thyroid Cancer and 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 .<br/>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.
dailymed-instance:descripti...
Levothyroxine Sodium Tablets, USP contain synthetic crystalline L-3,3',5,5'-tetraiodothyronine sodium salt [levothyroxine (T) sodium]. Synthetic Tis identical to that produced in the human thyroid gland. Levothyroxine (T) sodium has a molecular formula of CHIN NaO* HO, molecular weight of 798.86 g/mol (anhydrous), and structural formula as shown:<br/>Inactive Ingredients: Levothyroxine Sodium Tablets, USP, for oral administration, are available containing 25 mcg, 50 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg, 175 mcg, 200 mcg or 300 mcg of levothyroxine sodium. In addition, each tablet contains the following inactive ingredients: butylated hydroxyanisole, colloidal silicon dioxide, crospovidone, magnesium stearate, mannitol, microcrystalline cellulose, povidone, sodium lauryl sulfate and sucrose. The following are the coloring additives by tablet strength:
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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) and L-triiodothyronine (T), by the thyroid gland. Circulating serum Tand Tlevels exert a feedback effect on both TRH and TSH secretion. When serum Tand Tlevels increase, TRH and TSH secretion decrease. When thyroid hormone levels decrease, TRH and TSH secretion increase. 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. Tand Tdiffuse 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. 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 physiological actions of thyroid hormones are produced predominantly by T, the majority of which (approximately 80%) is derived from Tby deiodination in peripheral tissues. 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 .<br/>Pharmacokinetics:<br/>Absorption: Absorption of orally administered Tfrom the gastrointestinal (GI) tract ranges from 40% to 80%. The majority of the levothyroxine dose is absorbed from the jejunum and upper ileum. The relative bioavailability of levothyroxine sodium tablets, compared to an equal nominal dose of oral levothyroxine sodium solution, is approximately 99%. Tabsorption is increased by fasting, and decreased in malabsorption syndromes and by certain foods such as soybean infant formula. Dietary fiber decreases bioavailability of T. Absorption may also decrease with age. In addition, many drugs and foods affect Tabsorption .<br/>Distribution: Circulating thyroid hormones are greater than 99% bound to plasma proteins, including thyroxine-binding globulin (TBG), thyroxine-binding prealbumin (TBPA), and albumin (TBA), whose capacities and affinities vary for each hormone. The higher affinity of both TBG and TBPA for Tpartially explains the higher serum levels, slower metabolic clearance, and longer half-life of Tcompared to T. Protein-bound thyroid hormones exist in reverse equilibrium with small amounts of free hormone. Only unbound hormone is metabolically active. Many drugs and physiologic conditions affect the binding of thyroid hormones to serum proteins . Thyroid hormones do not readily cross the placental barrier .<br/>Metabolism: Tis slowly eliminated (see Table 1). The major pathway of thyroid hormone metabolism is through sequential deiodination. Approximately eighty-percent of circulating Tis derived from peripheral Tby monodeiodination. The liver is the major site of degradation for both Tand Twith Tdeiodination also occurring at a number of additional sites, including the kidney and other tissues. Approximately 80% of the daily dose of Tis deiodinated to yield equal amounts of Tand reverse T(rT). Tand rTare further deiodinated to diiodothyronine. Thyroid hormones are also metabolized via conjugation with glucuronides and sulfates and excreted directly into the bile and gut where they undergo enterohepatic recirculation.<br/>Elimination: Thyroid hormones are primarily eliminated by the kidneys. A portion of the conjugated hormone reaches the colon unchanged and is eliminated in the feces. Approximately 20% of Tis eliminated in the stool. Urinary excretion of Tdecreases with age.
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Levothyroxine sodium tablets are contraindicated in patients with untreated subclinical (suppressed serum TSH level with normal Tand Tlevels) or overt thyrotoxicosis of any etiology and in patients with acute myocardial infarction. Levothyroxine is contraindicated in patients with uncorrected adrenal insufficiency since thyroid hormones may precipitate an acute adrenal crisis by increasing the metabolic clearance of glucocorticoids . Levothyroxine sodium is contraindicated in patients with hypersensitivity to any of the inactive ingredients in levothyroxine sodium tablets.
dailymed-instance:supply
Levothyroxine Sodium Tablets, USP are available as caplet-shaped, biconvex tablets that are debossed with an M on one side of the tablet. The other side of each tablet is debossed with an L to the left of the score and an individual tablet identification number* to the right of the score. The scored side of the tablets is more fully described in the third column of the table, below: Store at 20��to 25��C (68��to 77��F). [See USP for Controlled Room Temperature]. Dispense in a tight, light-resistant container as defined in the USP using a child-resistant closure.
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WARNING: Thyroid hormones, including levothyroxine sodium, either alone or with other therapeutic agents, should not be used for the treatment of obesity or 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.
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Levothyroxine Sodium
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Levothyroxine Sodium (Tablet)
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Adverse reactions associated with levothyroxine therapy are primarily those of hyperthyroidism due to therapeutic overdosage . 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; Cardiovascular: palpitations, tachycardia, arrhythmias, increased pulse and blood pressure, heart failure, angina, myocardial infarction, cardiac arrest; Respiratory: dyspnea; Gastrointestinal: diarrhea, vomiting, abdominal cramps and elevations in liver function tests; Dermatologic: hair loss, flushing; Endocrine: decreased bone mineral density; Reproductive: menstrual irregularities, impaired fertility. 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 adult 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 GI symptoms (abdominal pain, nausea, vomiting and diarrhea), fever, arthralgia, serum sickness and wheezing. Hypersensitivity to levothyroxine itself is not known to occur.
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Levothyroxine sodium is used for the following indications:<br/>Hypothyroidism: As replacement or supplemental therapy in congenital or acquired hypothyroidism of any etiology, except transient hypothyroidism during the recovery phase of subacute thyroiditis. Specific indications include: primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) hypothyroidism and subclinical hypothyroidism. Primary hypothyroidism may result from functional deficiency, primary atrophy, partial or total congenital absence of the thyroid gland, or from the effects of surgery, radiation, or drugs, with or without the presence of goiter.<br/>Pituitary TSH Suppression: In the treatment or prevention of various types of euthyroid goiters , including thyroid nodules , subacute or chronic lymphocytic thyroiditis (Hashimoto's thyroiditis), multinodular goiter and, as an adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer.
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Levothyroxine Sodium