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Levothyroxine Sodium is a brand name for Levothyroxine (also known as Thyroxine). The medicine, its uses, side effects and dosage are the same regardless of brand.
Used for: 1 INDICATIONS AND USAGE Hypothyroidism Levothyroxine sodium tablets are indicated in adult and pediatric patients, including neonates, as a replacement therapy in primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) congenital or acquired hypothyroidism. Pituitary Thyrotropin (Thyroid‑Stimulating…
Verbatim from this product's FDA label. Tap a section to expand.
2 DOSAGE AND ADMINISTRATION Administer once daily, preferably on an empty stomach, one-half to one hour before breakfast with a full glass of water. 1) Administer at least 4 hours before or after drugs that are known to interfere with absorption.
1) Evaluate the need for dose adjustments when regularly administering within one hour of certain foods that may affect absorption. 1) Advise patients to stop biotin and biotin-containing supplements at least 2 days before assessing TSH and/or T4 levels.
2) Starting dose depends on a variety of factors, including age, body weight, cardiovascular status, and concomitant medications. Peak therapeutic effect may not be attained for 4 to 6 weeks. 2) See full prescribing information for dosing in specific patient populations.
3) Adequacy of therapy determined with periodic monitoring of TSH and/or T4 as well as clinical status. 1 Important Administration Instructions Administer levothyroxine sodium tablets as a single daily dose, on an empty stomach, one-half to one hour before breakfast with a full glass of water to avoid choking or gagging [see Adverse Reactions (6) ].
1) ]. 3) ]. Administer levothyroxine sodium tablets to pediatric patients who cannot swallow intact tablets by crushing the tablet, suspending the freshly crushed tablet in a small amount (5 to 10 mL) of water and immediately administering the suspension by spoon or dropper.
Ensure the patient ingests the full amount of the suspension. Do not store the suspension. 9) ]. 3) , Warnings and Precautions (5) , and Drug Interactions (7) ] . 4) ]. 3) ]. For secondary or tertiary hypothyroidism, serum TSH is not a reliable measure of levothyroxine sodium dosage adequacy and should not be used to monitor therapy.
3) ]. Inquire whether patients are taking biotin or biotin-containing supplements. 10) ]. The peak therapeutic effect of a given dose of levothyroxine sodium tablets may not be attained for 4 to 6 weeks. 3 Recommended Dosage and Titration Primary, Secondary, and Tertiary Hypothyroidism in Adults The recommended starting daily dosage of levothyroxine sodium tablets in adults with primary, secondary, or tertiary hypothyroidism is based on age and comorbid cardiac conditions, as described in Table 1.
For patients at risk of atrial fibrillation or patients with underlying cardiac disease, start with a lower dosage and titrate the dosage more slowly to avoid exacerbation of cardiac symptoms. 2) ]. Table 1. Levothyroxine Sodium Tablets Dosing Guidelines for Hypothyroidism in Adults* *Dosages greater than 200 mcg/day are seldom required.
6 ADVERSE REACTIONS Adverse reactions associated with levothyroxine sodium therapy are primarily those of hyperthyroidism due to therapeutic overdosage [see Warnings and Precautions (5) and 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: hair loss, flushing, rash Endocrine: decreased bone mineral density Reproductive: menstrual irregularities, impaired fertility Seizures have been reported rarely with the institution of levothyroxine therapy.
Adverse Reactions in Pediatric Patients Pseudotumor cerebri and slipped capital femoral epiphysis have been reported in pediatric patients receiving levothyroxine therapy. Overtreatment may result in craniosynostosis in infants who have not undergone complete closure of the fontanelles, and in premature closure of the epiphyses in pediatric patients still experiencing growth with resultant compromised adult height.
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 therapy are primarily those of hyperthyroidism due to therapeutic overdosage: arrhythmias, myocardial infarction, dyspnea, muscle spasm, headache, nervousness, irritability, insomnia, tremors, muscle weakness, increased appetite, weight loss, diarrhea, heat intolerance, menstrual irregularities, and skin rash.
5 WARNINGS AND PRECAUTIONS Serious risks related to overtreatment or undertreatment with levothyroxine sodium tablets: Titrate the dose of levothyroxine sodium carefully and monitor response to titration. 1) Cardiac adverse reactions in the elderly and in patients with underlying cardiovascular disease: Initiate levothyroxine sodium at less than the full replacement dose because of the increased risk of cardiac adverse reactions, including atrial fibrillation.
5) Myxedema coma: Do not use oral thyroid hormone drug products to treat myxedema coma. 3) Acute adrenal crisis in patients with concomitant adrenal insufficiency: Treat with replacement glucocorticoids prior to initiation of levothyroxine sodium treatment.
4) Worsening of diabetic control: Therapy in patients with diabetes mellitus may worsen glycemic control and result in increased antidiabetic agent or insulin requirements. Carefully monitor glycemic control after starting, changing, or discontinuing thyroid hormone therapy.
5) Decreased bone mineral density associated with thyroid hormone over-replacement: Over-replacement can increase bone resorption and decrease bone mineral density. Give the lowest effective dose. 1 Serious Risks Related to Overtreatment or Undertreatment with Levothyroxine Sodium Tablets Levothyroxine sodium tablets has a narrow therapeutic index.
Overtreatment or undertreatment with levothyroxine sodium tablets may have negative effects on growth and development, cardiovascular function, bone metabolism, reproductive function, cognitive function, gastrointestinal function, and glucose and lipid metabolism in adult or pediatric patients.
4) ]. 4)]. 3) ]. 2 Cardiac Adverse Reactions in the Elderly and in Patients with Underlying Cardiovascular Disease Over-treatment with levothyroxine may cause an increase in heart rate, cardiac wall thickness, and cardiac contractility and may precipitate angina or arrhythmias, particularly in patients with cardiovascular disease and in elderly patients.
4) ]. Uncorrected adrenal insufficiency. (4)
Not medical advice. Always read the patient information leaflet and follow your prescriber or pharmacist.
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1) and Drug Interactions (7) ]. 6 mcg/kg/day. Some patients require a lower starting dose. 5 to 25 mcg increments every 4 to 6 weeks, as needed until the patient is euthyroid. 6 mcg/kg/day) Titrate dosage every 6 to 8 weeks, as needed until the patient is euthyroid.
6 mcg/kg/day) Primary, Secondary, and Tertiary Hypothyroidism in Pediatric Patients The recommended starting daily dosage of levothyroxine sodium tablets in pediatric patients with primary, secondary, or tertiary hypothyroidism is based on body weight and changes with age as described in Table 2.
2) ]. Table 2. 4) ] . Pediatric Patients from Birth to 3 Months of Age at Risk for Cardiac Failure Start at a lower starting dosage and increase the dosage every 4 to 6 weeks as needed based on clinical and laboratory response. Pediatric Patients at Risk for Hyperactivity To minimize the risk of hyperactivity, start at one-fourth the recommended full replacement dosage, and increase on a weekly basis by one-fourth the full recommended replacement dosage until the full recommended replacement dosage is reached.
Hypothyroidism in Pregnant Patients For pregnant patients with pre-existing hypothyroidism, measure serum TSH and free-T4 as soon as pregnancy is confirmed and, at minimum, during each trimester of pregnancy. In pregnant patients with primary hypothyroidism, maintain serum TSH in the trimester-specific reference range.
The recommended daily dosage of levothyroxine sodium tablets in pregnant patients is described in Table 3. Table 3. 5 to 25 mcg per day. Monitor TSH every 4 weeks until a stable dose is reached and serum TSH is within normal trimester-specific range.
Reduce levothyroxine sodium dosage to pre-pregnancy levels immediately after delivery. Monitor serum TSH 4 to 8 weeks postpartum. 6 mcg/kg/day Monitor serum TSH every 4 weeks and adjust levothyroxine sodium dosage until serum TSH is within normal trimester-specific range.
0 mcg/kg/day TSH Suppression in Well-differentiated Thyroid Cancer in Adult and Pediatric Patients The levothyroxine sodium dosage is based on the target level of TSH suppression for the stage and clinical status of thyroid cancer.
4 Monitoring TSH and/or Thyroxine (T4) Levels Assess the adequacy of therapy by periodic assessment of laboratory tests and clinical evaluation. Biotin supplementation may interfere with immunoassays for TSH, T4, and T3, resulting in erroneous thyroid hormone test results.
10) ] . Persistent clinical and laboratory evidence of hypothyroidism despite an apparent adequate replacement dose of levothyroxine sodium may be evidence of inadequate absorption, poor compliance, drug interactions, or a combination of these factors.
Adults In adult patients with primary hypothyroidism, monitor serum TSH levels after an interval of 6 to 8 weeks after any change in dosage. In patients on a stable and appropriate replacement dosage, evaluate clinical and biochemical response every 6 to 12 months and whenever there is a change in the patient’s clinical status.
Pediatric Patients In patients with hypothyroidism, assess the adequacy of replacement therapy by measuring both serum TSH and total or free-T4. Monitor TSH and total or free-T4 in pediatric patients as follows: 2 and 4 weeks after the initiation of treatment, 2 weeks after any change in dosage, and then every 3 to 12 months thereafter following dosage stabilization until growth is completed.
Poor compliance or abnormal values may necessitate more frequent monitoring. Perform routine clinical examination, including assessment of development, mental and physical growth, and bone maturation, at regular intervals. The general aim of therapy is to normalize the serum TSH level.
TSH may not normalize in some patients due to in utero hypothyroidism causing a resetting of pituitary-thyroid feedback. Failure of the serum T4 to increase into the upper half of the normal range within 2 weeks of initiation of levothyroxine sodium therapy and/or of the serum TSH to decrease below 20 mIU per litre within 4 weeks may indicate the patient is not receiving adequate therapy.
4) ] . Secondary and Tertiary Hypothyroidism Monitor serum free-T4 levels and maintain in the upper half of the normal range in these patients. 1 Important Administration Instructions Administer levothyroxine sodium tablets as a single daily dose, on an empty stomach, one-half to one hour before breakfast with a full glass of water to avoid choking or gagging [see Adverse Reactions (6) ].
1) ]. 3) ]. Administer levothyroxine sodium tablets to pediatric patients who cannot swallow intact tablets by crushing the tablet, suspending the freshly crushed tablet in a small amount (5 to 10 mL) of water and immediately administering the suspension by spoon or dropper.
Ensure the patient ingests the full amount of the suspension. Do not store the suspension. 9) ]. 3) , Warnings and Precautions (5) , and Drug Interactions (7) ] . 4) ]. 3) ]. For secondary or tertiary hypothyroidism, serum TSH is not a reliable measure of levothyroxine sodium dosage adequacy and should not be used to monitor therapy.
3) ]. Inquire whether patients are taking biotin or biotin-containing supplements. 10) ]. The peak therapeutic effect of a given dose of levothyroxine sodium tablets may not be attained for 4 to 6 weeks. 3 Recommended Dosage and Titration Primary, Secondary, and Tertiary Hypothyroidism in Adults The recommended starting daily dosage of levothyroxine sodium tablets in adults with primary, secondary, or tertiary hypothyroidism is based on age and comorbid cardiac conditions, as described in Table 1.
For patients at risk of atrial fibrillation or patients with underlying cardiac disease, start with a lower dosage and titrate the dosage more slowly to avoid exacerbation of cardiac symptoms. 2) ]. Table 1. Levothyroxine Sodium Tablets Dosing Guidelines for Hypothyroidism in Adults* *Dosages greater than 200 mcg/day are seldom required.
1) and Drug Interactions (7) ]. 6 mcg/kg/day. Some patients require a lower starting dose. 5 to 25 mcg increments every 4 to 6 weeks, as needed until the patient is euthyroid. 6 mcg/kg/day) Titrate dosage every 6 to 8 weeks, as needed until the patient is euthyroid.
6 mcg/kg/day) Primary, Secondary, and Tertiary Hypothyroidism in Pediatric Patients The recommended starting daily dosage of levothyroxine sodium tablets in pediatric patients with primary, secondary, or tertiary hypothyroidism is based on body weight and changes with age as described in Table 2.
2) ]. Table 2. 4) ] . Pediatric Patients from Birth to 3 Months of Age at Risk for Cardiac Failure Start at a lower starting dosage and increase the dosage every 4 to 6 weeks as needed based on clinical and laboratory response. Pediatric Patients at Risk for Hyperactivity To minimize the risk of hyperactivity, start at one-fourth the recommended full replacement dosage, and increase on a weekly basis by one-fourth the full recommended replacement dosage until the full recommended replacement dosage is reached.
Hypothyroidism in Pregnant Patients For pregnant patients with pre-existing hypothyroidism, measure serum TSH and free-T4 as soon as pregnancy is confirmed and, at minimum, during each trimester of pregnancy. In pregnant patients with primary hypothyroidism, maintain serum TSH in the trimester-specific reference range.
The recommended daily dosage of levothyroxine sodium tablets in pregnant patients is described in Table 3. Table 3. 5 to 25 mcg per day. Monitor TSH every 4 weeks until a stable dose is reached and serum TSH is within normal trimester-specific range.
Reduce levothyroxine sodium dosage to pre-pregnancy levels immediately after delivery. Monitor serum TSH 4 to 8 weeks postpartum. 6 mcg/kg/day Monitor serum TSH every 4 weeks and adjust levothyroxine sodium dosage until serum TSH is within normal trimester-specific range.
0 mcg/kg/day TSH Suppression in Well-differentiated Thyroid Cancer in Adult and Pediatric Patients The levothyroxine sodium dosage is based on the target level of TSH suppression for the stage and clinical status of thyroid cancer.
Primary, Secondary, and Tertiary Hypothyroidism in Adults The recommended starting daily dosage of levothyroxine sodium tablets in adults with primary, secondary, or tertiary hypothyroidism is based on age and comorbid cardiac conditions, as described in Table 1.
For patients at risk of atrial fibrillation or patients with underlying cardiac disease, start with a lower dosage and titrate the dosage more slowly to avoid exacerbation of cardiac symptoms. 2) ]. Table 1. Levothyroxine Sodium Tablets Dosing Guidelines for Hypothyroidism in Adults* *Dosages greater than 200 mcg/day are seldom required.
1) and Drug Interactions (7) ]. 6 mcg/kg/day. Some patients require a lower starting dose. 5 to 25 mcg increments every 4 to 6 weeks, as needed until the patient is euthyroid. 6 mcg/kg/day) Titrate dosage every 6 to 8 weeks, as needed until the patient is euthyroid.
6 mcg/kg/day) Primary, Secondary, and Tertiary Hypothyroidism in Pediatric Patients The recommended starting daily dosage of levothyroxine sodium tablets in pediatric patients with primary, secondary, or tertiary hypothyroidism is based on body weight and changes with age as described in Table 2.
2) ]. Table 2. 4) ] . Pediatric Patients from Birth to 3 Months of Age at Risk for Cardiac Failure Start at a lower starting dosage and increase the dosage every 4 to 6 weeks as needed based on clinical and laboratory response. Pediatric Patients at Risk for Hyperactivity To minimize the risk of hyperactivity, start at one-fourth the recommended full replacement dosage, and increase on a weekly basis by one-fourth the full recommended replacement dosage until the full recommended replacement dosage is reached.
Hypothyroidism in Pregnant Patients For pregnant patients with pre-existing hypothyroidism, measure serum TSH and free-T4 as soon as pregnancy is confirmed and, at minimum, during each trimester of pregnancy. In pregnant patients with primary hypothyroidism, maintain serum TSH in the trimester-specific reference range.
The recommended daily dosage of levothyroxine sodium tablets in pregnant patients is described in Table 3. Table 3. 5 to 25 mcg per day. Monitor TSH every 4 weeks until a stable dose is reached and serum TSH is within normal trimester-specific range.
Reduce levothyroxine sodium dosage to pre-pregnancy levels immediately after delivery. Monitor serum TSH 4 to 8 weeks postpartum. 6 mcg/kg/day Monitor serum TSH every 4 weeks and adjust levothyroxine sodium dosage until serum TSH is within normal trimester-specific range.
0 mcg/kg/day TSH Suppression in Well-differentiated Thyroid Cancer in Adult and Pediatric Patients The levothyroxine sodium dosage is based on the target level of TSH suppression for the stage and clinical status of thyroid cancer.
4 Monitoring TSH and/or Thyroxine (T4) Levels Assess the adequacy of therapy by periodic assessment of laboratory tests and clinical evaluation. Biotin supplementation may interfere with immunoassays for TSH, T4, and T3, resulting in erroneous thyroid hormone test results.
10) ] . Persistent clinical and laboratory evidence of hypothyroidism despite an apparent adequate replacement dose of levothyroxine sodium may be evidence of inadequate absorption, poor compliance, drug interactions, or a combination of these factors.
Adults In adult patients with primary hypothyroidism, monitor serum TSH levels after an interval of 6 to 8 weeks after any change in dosage. In patients on a stable and appropriate replacement dosage, evaluate clinical and biochemical response every 6 to 12 months and whenever there is a change in the patient’s clinical status.
Pediatric Patients In patients with hypothyroidism, assess the adequacy of replacement therapy by measuring both serum TSH and total or free-T4. Monitor TSH and total or free-T4 in pediatric patients as follows: 2 and 4 weeks after the initiation of treatment, 2 weeks after any change in dosage, and then every 3 to 12 months thereafter following dosage stabilization until growth is completed.
Poor compliance or abnormal values may necessitate more frequent monitoring. Perform routine clinical examination, including assessment of development, mental and physical growth, and bone maturation, at regular intervals. The general aim of therapy is to normalize the serum TSH level.
TSH may not normalize in some patients due to in utero hypothyroidism causing a resetting of pituitary-thyroid feedback. Failure of the serum T4 to increase into the upper half of the normal range within 2 weeks of initiation of levothyroxine sodium therapy and/or of the serum TSH to decrease below 20 mIU per litre within 4 weeks may indicate the patient is not receiving adequate therapy.
4) ] . Secondary and Tertiary Hypothyroidism Monitor serum free-T4 levels and maintain in the upper half of the normal range in these patients. Adults In adult patients with primary hypothyroidism, monitor serum TSH levels after an interval of 6 to 8 weeks after any change in dosage.
In patients on a stable and appropriate replacement dosage, evaluate clinical and biochemical response every 6 to 12 months and whenever there is a change in the patient’s clinical status. Pediatric Patients In patients with hypothyroidism, assess the adequacy of replacement therapy by measuring both serum TSH and total or free-T4.
Monitor TSH and total or free-T4 in pediatric patients as follows: 2 and 4 weeks after the initiation of treatment, 2 weeks after any change in dosage, and then every 3 to 12 months thereafter following dosage stabilization until growth is completed.
Poor compliance or abnormal values may necessitate more frequent monitoring. Perform routine clinical examination, including assessment of development, mental and physical growth, and bone maturation, at regular intervals. The general aim of therapy is to normalize the serum TSH level.
TSH may not normalize in some patients due to in utero hypothyroidism causing a resetting of pituitary-thyroid feedback. Failure of the serum T4 to increase into the upper half of the normal range within 2 weeks of initiation of levothyroxine sodium therapy and/or of the serum TSH to decrease below 20 mIU per litre within 4 weeks may indicate the patient is not receiving adequate therapy.
4) ] . Secondary and Tertiary Hypothyroidism Monitor serum free-T4 levels and maintain in the upper half of the normal range in these patients.
(6) To report SUSPECTED ADVERSE REACTIONS, contact Accord Healthcare Inc. gov/medwatch.
5) ]. Monitor for cardiac arrhythmias during surgical procedures in patients with coronary artery disease receiving suppressive levothyroxine sodium therapy. Monitor patients receiving concomitant levothyroxine sodium and sympathomimetic agents for signs and symptoms of coronary insufficiency.
If cardiac symptoms develop or worsen, reduce the levothyroxine sodium tablets dose or withhold for one week and restart at a lower dose. 3 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.
Use of oral thyroid hormone drug products is not recommended to treat myxedema coma. Administer thyroid hormone products formulated for intravenous administration to treat myxedema coma. 4 Acute Adrenal Crisis in Patients with Concomitant Adrenal Insufficiency Thyroid hormone increases metabolic clearance of glucocorticoids.
Initiation of thyroid hormone therapy prior to initiating glucocorticoid therapy may precipitate an acute adrenal crisis in patients with adrenal insufficiency. Treat patients with adrenal insufficiency with replacement glucocorticoids prior to initiating treatment with levothyroxine sodium [see Contraindications (4) ] .
5 Worsening of Diabetic Control Addition of levothyroxine therapy in patients with diabetes mellitus may worsen glycemic control and result in increased antidiabetic agent or insulin requirements. 2) ] . 6 Decreased Bone Mineral Density Associated with Thyroid Hormone Over-Replacement Increased bone resorption and decreased bone mineral density may occur as a result of levothyroxine over-replacement, particularly in post-menopausal women.
The increased bone resorption may be associated with increased serum levels and urinary excretion of calcium and phosphorous, elevations in bone alkaline phosphatase, and suppressed serum parathyroid hormone levels. Administer the minimum dose of levothyroxine sodium that achieves the desired clinical and biochemical response to mitigate this risk.
7 Risk of Allergic Reactions Due to Tartrazine This product contains FD&C Yellow No. 5 (tartrazine) which may cause allergic-type reactions (including bronchial asthma) in certain susceptible persons. Although the overall incidence of FD&C Yellow No.
5 (tartrazine) sensitivity in the general population is low, it is frequently seen in patients who also have aspirin hypersensitivity. 1 Serious Risks Related to Overtreatment or Undertreatment with Levothyroxine Sodium Tablets Levothyroxine sodium tablets has a narrow therapeutic index.
Overtreatment or undertreatment with levothyroxine sodium tablets may have negative effects on growth and development, cardiovascular function, bone metabolism, reproductive function, cognitive function, gastrointestinal function, and glucose and lipid metabolism in adult or pediatric patients.
4) ]. 4)]. 3) ]. 2 Cardiac Adverse Reactions in the Elderly and in Patients with Underlying Cardiovascular Disease Over-treatment with levothyroxine may cause an increase in heart rate, cardiac wall thickness, and cardiac contractility and may precipitate angina or arrhythmias, particularly in patients with cardiovascular disease and in elderly patients.
5) ]. Monitor for cardiac arrhythmias during surgical procedures in patients with coronary artery disease receiving suppressive levothyroxine sodium therapy. Monitor patients receiving concomitant levothyroxine sodium and sympathomimetic agents for signs and symptoms of coronary insufficiency.
If cardiac symptoms develop or worsen, reduce the levothyroxine sodium tablets dose or withhold for one week and restart at a lower dose. 3 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.
Use of oral thyroid hormone drug products is not recommended to treat myxedema coma. Administer thyroid hormone products formulated for intravenous administration to treat myxedema coma. 4 Acute Adrenal Crisis in Patients with Concomitant Adrenal Insufficiency Thyroid hormone increases metabolic clearance of glucocorticoids.
Initiation of thyroid hormone therapy prior to initiating glucocorticoid therapy may precipitate an acute adrenal crisis in patients with adrenal insufficiency. Treat patients with adrenal insufficiency with replacement glucocorticoids prior to initiating treatment with levothyroxine sodium [see Contraindications (4) ] .
5 Worsening of Diabetic Control Addition of levothyroxine therapy in patients with diabetes mellitus may worsen glycemic control and result in increased antidiabetic agent or insulin requirements. 2) ] . 6 Decreased Bone Mineral Density Associated with Thyroid Hormone Over-Replacement Increased bone resorption and decreased bone mineral density may occur as a result of levothyroxine over-replacement, particularly in post-menopausal women.
The increased bone resorption may be associated with increased serum levels and urinary excretion of calcium and phosphorous, elevations in bone alkaline phosphatase, and suppressed serum parathyroid hormone levels. Administer the minimum dose of levothyroxine sodium that achieves the desired clinical and biochemical response to mitigate this risk.
7 Risk of Allergic Reactions Due to Tartrazine This product contains FD&C Yellow No. 5 (tartrazine) which may cause allergic-type reactions (including bronchial asthma) in certain susceptible persons. Although the overall incidence of FD&C Yellow No.
5 (tartrazine) sensitivity in the general population is low, it is frequently seen in patients who also have aspirin hypersensitivity. 1) ] . Soybean flour, cottonseed meal, walnuts, and dietary fiber may bind and decrease the absorption of levothyroxine sodium from the gastrointestinal tract.
Grapefruit juice may delay the absorption of levothyroxine and reduce its bioavailability. 10 Drug-Laboratory Test Interactions Thyroxine-binding Globulin (TBG) 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 concentration.
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 9000.
Biotin Biotin supplementation is known to interfere with thyroid hormone immunoassays that are based on a biotin and streptavidin interaction, which may result in erroneous thyroid hormone test results. Stop biotin and biotin-containing supplements for at least 2 days prior to thyroid testing.