Dosage & Administration
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Tirosint Prescribing Information
- Thyroid hormones, including TIROSINT, 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 [see Adverse Reactions (6), Drug Interactions (7.7), and Overdosage (10)].
Hypothyroidism
TIROSINT is indicated as a replacement therapy in adults and pediatric patients 6 years and older with primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) congenital or acquired hypothyroidism.
Pituitary Thyrotropin (Thyroid-Stimulating Hormone, TSH) Suppression
TIROSINT is indicated as an adjunct to surgery and radioiodine therapy in the management of adults and pediatric patients 6 years and older with thyrotropin-dependent well-differentiated thyroid cancer.
Limitations of Use:
- TIROSINT is not indicated for suppression of benign thyroid nodules and nontoxic diffuse goiter in iodine-sufficient patients as there are no clinical benefits and overtreatment with TIROSINT may induce hyperthyroidism [see Warnings and Precautions (5.4)].
- TIROSINT is not indicated for treatment of transient hypothyroidism during the recovery phase of subacute thyroiditis.
General Administration Information
Administer TIROSINT as a single daily oral dose, on an empty stomach, one-half to one hour before breakfast.
Administer TIROSINT at least 4 hours before or after drugs known to interfere with TIROSINT absorption [see Drug Interactions (7.1)]
Evaluate the need for dose adjustments when regularly administering within an hour of certain foods that may affect TIROSINT absorption [see Drug Interactions (7.9) and Clinical Pharmacology (12.3)].
Swallow TIROSINT capsules whole, do not cut, crush, or chew.
General Principles of Dosing
The dose of TIROSINT 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 [see Dosage and Administration (2.3), Warnings and Precautions (5), and Drug Interactions (7)] . Dosing must be individualized to account for these factors and dose adjustments made based on periodic assessment of the patient's clinical response and laboratory parameters [see Dosage and Administration (2.4)].
The peak therapeutic effect of a given dose of TIROSINT may not be attained for 4 to 6 weeks.
Dosing In Specific Patient Populations
Primary Hypothyroidism in Adults and in Adolescents in Whom Growth and Puberty are Complete
Start TIROSINT at the full replacement dose in otherwise healthy, non-elderly individuals who have been hypothyroid for only a short time (such as a few months).The average full replacement dose of TIROSINT is approximately 1.6 mcg per kg per day (for example: 100-125 mcg per day for a 70 kg adult).
Adjust the dose by 12.5 to 25 mcg increments every 4 to 6 weeks until the patient is clinically euthyroid and the serum TSH returns to normal. Doses greater than 200 mcg per day are seldom required. An inadequate response to daily doses greater than 300 mcg per day is rare and may indicate poor compliance, malabsorption, drug interactions, or a combination of these factors.
For elderly patients or patients with underlying cardiovascular disease, start with a dose of 12.5 to 25 mcg per day. Increase the dose every 6 to 8 weeks, as needed, until the patient is clinically euthyroid and the serum TSH returns to normal. The full replacement dose of TIROSINT may be less than 1 mcg per kg per day in elderly patients.
In patients with severe longstanding hypothyroidism, start with a dose of 12.5 to 25 mcg per day. Adjust the dose in 12.5 to 25 mcg increments every 2 to 4 weeks until the patient is clinically euthyroid and the serum TSH level is normalized.
Secondary or Tertiary Hypothyroidism
Start TIROSINT at the full replacement dose in otherwise healthy, non-elderly individuals. Start with a lower dose in elderly patients with underlying cardiovascular disease or patients with severe longstanding hypothyroidism as described above. Serum TSH is not a reliable measure of TIROSINT dose adequacy in patients with secondary or tertiary hypothyroidism, and should not be used to monitor therapy. Use the serum free-T4 level to monitor adequacy of therapy in this patient population. Titrate TIROSINT dosing per above instructions until the patient is clinically euthyroid and the serum free-T4 level is restored to the upper half of the normal range.
Pediatric Dosage - Congenital or Acquired Hypothyroidism
Only administer TIROSINT to pediatric patients 6 years and older who are able to swallow an intact capsule .
The recommended daily dose of TIROSINT in pediatric patients with hypothyroidism is based on body weight and changes with age as described in Table 1. Start TIROSINT at the full daily dose in most pediatric patients. Start at a lower dose in children at risk for hyperactivity (see below). Monitor for clinical and laboratory response [see Dosage and Administration (2.4)] .
| Age | Daily Dose Per Kg Body Weight * |
|---|---|
| |
| 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 |
Children at risk for hyperactivity: To minimize the risk of hyperactivity in children, start at one-fourth the recommended full replacement dose, and increase on a weekly basis by one-fourth the full-recommended replacement dose until the full recommended replacement dose is reached.
Pregnancy
Preexisting Hypothyroidism: TIROSINT dose requirements may increase during pregnancy . Measure serum TSH and free-T4 as soon as pregnancy is confirmed and, at a minimum, during each trimester of pregnancy. In patients with primary hypothyroidism, maintain serum TSH in the trimester-specific reference range. For patients with serum TSH above the normal trimester specific range, increase the dose of TIROSINT by 12.5 to 25 mcg per day and measure TSH every four weeks until a stable TIROSINT dose is reached and serum TSH is within the normal trimester specific range. Reduce TIROSINT dosage to pre-pregnancy levels immediately after delivery and measure serum TSH levels 4 to 8 weeks postpartum to ensure the TIROSINT dose is appropriate.
New Onset Hypothyroidism: Normalize thyroid function as rapidly as possible. In patients with moderate to severe signs and symptoms of hypothyroidism, start TIROSINT at the full replacement dose (1.6 mcg per kg body weight per day). In patients with mild hypothyroidism (TSH < 10 mIU per Liter), start TIROSINT at 1.0 mcg per kg body weight per day. Evaluate serum TSH every 4 weeks and adjust TIROSINT dosage until serum TSH is within the normal trimester specific range [see Use in Specific Populations (8.1)].
TSH Suppression in Well-Differentiated Thyroid Cancer
Generally, TSH is suppressed to below 0.1 mIU per Liter, and this usually requires a TIROSINT dose of greater than 2 mcg per kg per day. However, in patients with high-risk tumors, the target level for TSH suppression may be lower.
Monitoring TSH and/or Thyroxine (T4) Levels
Assess the adequacy of therapy by periodic assessment of laboratory tests and clinical evaluation. Persistent clinical and laboratory evidence of hypothyroidism despite an apparent adequate replacement dose of TIROSINT 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 dose. In patients on a stable and appropriate replacement dose, evaluate clinical and biochemical response every 6 to 12 months and whenever there is a change in the patient's clinical status.
Pediatrics
In patients with congenital 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 children is as follows: at 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 dose stabilization until growth is completed. Poor compliance or abnormal values may necessitate more frequent monitoring. Perform routine clinical examination, including assessment of mental and physical growth and development, and bone maturation at regular intervals.
While 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 the pituitary-thyroid feedback. Failure of the serum T4 to increase into the upper half of the normal range within 2 weeks of initiation of TIROSINT therapy and/or of the serum TSH to decrease below 20 mIU per Liter within 4 weeks may indicate the child is not receiving adequate therapy. Assess compliance, dose of medication administered, and method of administration prior to increasing the dose of TIROSINT [see Warnings and Precautions (5.4) and Use in Specific Populations (8.4)] .
Secondary (Pituitary) and Tertiary (Hypothalamic) Hypothyroidism
Monitor serum free-T4 levels maintain in the upper half of the normal range in these patients.
TIROSINT capsules are amber-colored, round/biconvex capsules, imprinted with a dosage strength specific letter on one side and containing a viscous amber-colored liquid and are available as follows:
| Strength (mcg) | Imprint Code |
|---|---|
| 13 | A |
| 25 | E |
| 37.5 | O |
| 44 | R |
| 50 | G |
| 62.5 | L |
| 75 | H |
| 88 | J |
| 100 | K |
| 112 | M |
| 125 | N |
| 137 | P |
| 150 | S |
| 175 | U |
| 200 | Y |
Pregnancy
Risk Summary
Experience with levothyroxine use in pregnant women, including data from post-marketing studies, have not reported increased rates of major birth defects or miscarriages [see Data]. There are risks to the mother and fetus associated with untreated hypothyroidism in pregnancy. Since thyroid-stimulating hormone (TSH) levels may increase during pregnancy, TSH should be monitored and TIROSINT dosage adjusted during pregnancy [see Clinical Considerations] . There are no animal studies conducted with levothyroxine during pregnancy. TIROSINT should not be discontinued during pregnancy and hypothyroidism diagnosed during pregnancy should be promptly treated.
The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively.
Clinical Considerations
Disease-Associated Maternal and/or Embryo/Fetal Risk
Maternal hypothyroidism during pregnancy is associated with a higher rate of complications, including spontaneous abortion, gestational hypertension, pre-eclampsia, stillbirth, and premature delivery. Untreated maternal hypothyroidism may have an adverse effect on fetal neurocognitive development.
Dose Adjustments During Pregnancy and the Postpartum Period
Pregnancy may increase TIROSINT requirements. Serum TSH level should be monitored and the TIROSINT dosage adjusted during pregnancy. Since postpartum TSH levels are similar to preconception values, the TIROSINT dosage should return to the pre-pregnancy dose immediately after delivery [see Dosage and Administration (2.3)].
Data
Human Data
Levothyroxine is approved for use as a replacement therapy for hypothyroidism. There is a long experience of levothyroxine use in pregnant women, including data from post-marketing studies that have not reported increased rates of fetal malformations, miscarriages or other adverse maternal or fetal outcomes associated with levothyroxine use in pregnant women.
Lactation
Risk Summary
Limited published studies report that levothyroxine is present in human milk. However, there is insufficient information to determine the effects of levothyroxine on the breastfed infant and no available information on the effects of levothyroxine on milk production. Adequate levothyroxine treatment during lactation may normalize milk production in hypothyroid lactating mothers. The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for TIROSINT and any potential adverse effects on the breastfed infant from TIROSINT or from the underlying maternal condition.
Pediatric Use
TIROSINT is indicated for use in pediatric patients 6 years and older. The initial dose of TIROSINT varies with age and body weight. Dosing adjustments are based on an assessment of the individual patient's clinical and laboratory parameters [see Dosage and Administration (2.3, 2.4)]
In children in whom a diagnosis of permanent hypothyroidism has not been established, discontinue TIROSINT administration for a trial period. Obtain serum T4 and TSH levels at the end of the trial period, and use laboratory test results and clinical assessments to guide diagnosis and treatment, if warranted.
Congenital Hypothyroidism [see Dosage and Administration (2.3, 2.4)]
Rapid restoration of normal serum T4 concentrations is essential for preventing the adverse effects of congenital hypothyroidism on intellectual development as well as on overall physical growth and maturation. Therefore, initiate levothyroxine therapy immediately upon diagnosis. Levothyroxine is generally continued for life in these patients.
Closely monitor children during the first two weeks of TIROSINT therapy for cardiac overload and arrhythmias.
Closely monitor patients to avoid undertreatment and overtreatment. Undertreatment may have deleterious effects on intellectual development and linear growth. Overtreatment may adversely affect the tempo of brain maturation and accelerate the bone age with resultant premature closure of the epiphyses and compromised adult stature.
Acquired Hypothyroidism in Pediatric Patients
Closely monitor patients to avoid undertreatment and overtreatment. Undertreatment may result in poor school performance due to impaired concentration and slowed mentation and in reduced adult height. Overtreatment may accelerate the bone age and result in premature epiphyseal closure and compromised adult stature.
Treated children may manifest a period of catch-up growth, which may be adequate in some cases to normalize adult height. In children with severe or prolonged hypothyroidism, catch-up growth may not be adequate to normalize adult height.
Geriatric Use
Because of the increased prevalence of cardiovascular disease among the elderly, initiate TIROSINT therapy at less than the full replacement dose [ see Warnings and Precautions (5.1) and Dosage and Administration (2.3)]. Atrial arrhythmias can occur in elderly patients. Atrial fibrillation is the most common of the arrhythmias observed with levothyroxine overtreatment in the elderly .
TIROSINT is contraindicated in patients with uncorrected adrenal insufficiency [see Warnings and Precautions (5.3)].