Levothyroxinedosage

Administer once daily, preferably on an empty stomach, one-half to one hour before breakfast. Administer at least 4 hours before or after drugs that are known to interfere with absorption. Evaluate the need for dose adjustments when regularly administering within one hour of certain foods that may affect absorption. Advise patients to stop biotin and biotin-containing supplements at least 2 days before assessing TSH and/or T4 levels. 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 4-6 weeks. See full prescribing information for dosing in specific patient populations. Adequacy of therapy determined with periodic monitoring of TSH and/or T4 as well as clinical status.

2.1 Important

Administration Instructions Administer SYNTHROID as a single daily dose, on an empty stomach, one-half to one hour before breakfast. Administer SYNTHROID at least 4 hours before or after drugs known to interfere with SYNTHROID absorption. Evaluate the need for dosage adjustments when regularly administering within one hour of certain foods that may affect SYNTHROID absorption. Administer SYNTHROID 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. Do not administer in foods that decrease absorption of SYNTHROID, such as soybean-based infant formula.

2.2 Important

Considerations for Dosing The dosage of SYNTHROID for hypothyroidism or pituitary TSH suppression depends on a variety of factors including: the patient's age, body weight, cardiovascular status, concomitant medical conditions (including pregnancy), concomitant medications, co-administered food and the specific nature of the condition being treated. Dosing must be individualized to account for these factors and dosage adjustments made based on periodic assessment of the patient's clinical response and laboratory parameters. For adult patients with primary hypothyroidism, titrate until the patient is clinically euthyroid and the serum TSH returns to normal. For secondary or tertiary hypothyroidism, serum TSH is not a reliable measure of SYNTHROID dosage adequacy and should not be used to monitor therapy. Use the serum free-T4 level to titrate SYNTHROID dosing until the patient is clinically euthyroid and the serum free-T4 level is restored to the upper half of the normal range. Inquire whether patients are taking biotin or biotin-containing supplements. If so, advise them to stop biotin supplementation at least 2 days before assessing TSH and/or T4 levels. The peak therapeutic effect of a given dose of SYNTHROID may not be attained for 4 to 6 weeks.

2.3 Recommended

Dosage and Titration Primary, Secondary, and Tertiary Hypothyroidism in Adults The recommended starting daily dosage of SYNTHROID 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. Dosage titration is based on serum TSH or free-T4. Table 1. SYNTHROID Dosing Guidelines for Hypothyroidism in Adults* Patient Population Starting Dosage Dosage Titration Based on Serum TSH or Free-T4 Adults diagnosed with hypothyroidism Full replacement dose is 1.6 mcg/kg/day. Some patients require a lower starting dose. Titrate dosage by 12.5 to 25 mcg increments every 4 to 6 weeks, as needed until the patient is euthyroid. Adults at risk for atrial fibrillation or with underlying cardiac disease Lower starting dose (less than 1.6 mcg/kg/day) Titrate dosage every 6 to 8 weeks, as needed until the patient is euthyroid. Geriatric patients Lower starting dose (less than 1.6 mcg/kg/day) * Dosages greater than 200 mcg/day are seldom required. An inadequate response to daily dosages greater than 300 mcg/day is rare and may indicate poor compliance, malabsorption, drug interactions, or a combination of these factors. Primary, Secondary, and Tertiary Hypothyroidism in Pediatric Patients The recommended starting daily dosage of SYNTHROID in pediatric patients with primary, secondary, or tertiary hypothyroidism is based on body weight and changes with age as described in Table 2. Titrate the dosage (every 2 weeks) as needed based on serum TSH or free-T4 until the patient is euthyroid. Table 2. SYNTHROID Dosing Guidelines for Hypothyroidism in Pediatric Patients Ag e Starting Daily Dos ag e Per Kg Body Weight * 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 Greater than 12 years but growth and puberty incomplete 2-3 mcg/kg/day Growth and puberty complete 1.6 mcg/kg/day * Adjust dosage based on clinical response and laboratory parameters. 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 SYNTHROID in pregnant patients is described in Table 3. Table 3. SYNTHROID Dosing Guidelines for Hypothyroidism in Pregnant Patients Patient Population Starting Dosage Dose Adjustment and Titration Pre-existing primary hypothyroidism with serum TSH above normal trimester-specific range Pre-pregnancy dosage may increase during pregnancy Increase SYNTHROID dosage by 12.5 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 SYNTHROID dosage to pre-pregnancy levels immediately after delivery. Monitor serum TSH 4 to 8 weeks postpartum. New onset hypothyroidism (TSH ≥ 10 mIU per liter) 1.6 mcg/kg/day Monitor serum TSH every 4 weeks and adjust SYNTHROID dosage until serum TSH is within normal trimester-specific range. New onset hypothyroidism (TSH < 10 mIU per liter) 1.0 mcg/kg/day TSH Suppression in Well-differentiated Thyroid Cancer in Adult and Pediatric Patients The SYNTHROID dosage is based on the target level of TSH suppression for the stage and clinical status of thyroid cancer.

2.4 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. Stop biotin and biotin-containing supplements for at least 2 days before assessing TSH and/or T4 levels. Persistent clinical and laboratory evidence of hypothyroidism despite an apparent adequate replacement dose of SYNTHROID 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 SYNTHROID therapy and/or of the serum TSH to decrease below 20 mIU per liter within 4 weeks may indicate the patient is not receiving adequate therapy. Assess compliance, dose of medication administered, and method of administration prior to increasing the dose of SYNTHROID. Secondary and Tertiary Hypothyroidism Monitor serum free-T4 levels and maintain in the upper half of the normal range in these patients.