What is Levothyroxine and how is it used?
Levothyroxine belongs to a class of drugs called Thyroid Products.
It is not known if Levothyroxine is safe and effective in children younger than 1 month of age.
What are side effects of Levothyroxine?
Common side effects of Levothyroxine are primarily those of hyperthyroidism due to therapeutic overdosage and include:
- difficulty breathing,
- swelling of your face, lips, tongue, or throat,
- chest pain or pressure,
- little or no urination,
- difficulty swallowing,
- dilated neck veins,
- extreme fatigue,
- fast, slow, irregular, pounding, or racing heartbeat or pulse,
- heat intolerance,
- irregular breathing,
- menstrual changes,
- pain or discomfort in the arms, jaw, back, or neck,
- blurred or double vision,
- eye pain,
- slowed growth in children,
- pain in the hip or knee,
- severe headache,
- change in consciousness,
- cold, clammy skin,
- fast or weak pulse,
- loss of consciousness,
- loss of coordination, and
- slurring of speech
Get medical help right away, if you have any of the symptoms listed above.
The most common side effects of Levothyroxine include:
- abdominal or stomach cramps,
- change in appetite,
- false or unusual sense of well-being,
- feeling unwell,
- flushing or warmth,
- suspicion or distrust,
- hair loss,
- increased appetite,
- muscle weakness,
- mood swings,
- redness of the face, neck, arms, and occasionally, upper chest,
- vomiting, and
- weight gain or loss
Tell the doctor if you have any side effect that bothers you or that does not go away.
These are not all the possible side effects of Levothyroxine. For more information, ask your doctor or pharmacist.
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
LEVOTHYROXINE is indicated in pediatric and adult patients as a replacement therapy in primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) congenital or acquired hypothyroidism.
Pituitary Thyrotropin (Thyroid-Stimulating Hormone, TSH) Suppression
LEVOTHYROXINE is indicated in pediatric and adult patients as an adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer.
Limitations Of Use
- LEVOTHYROXINE 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 LEVOTHYROXINE may induce hyperthyroidism [see WARNINGS AND PRECAUTIONS].
- LEVOTHYROXINE is not indicated for treatment of hypothyroidism during the recovery phase of subacute thyroiditis.
DOSAGE AND ADMINISTRATION
General Administration Information
Administer LEVOTHYROXINE tablets orally as a single daily dose, on an empty stomach, one-half to one hour before breakfast.
Administer LEVOTHYROXINE at least 4 hours before or after drugs known to interfere with LEVOTHYROXINE absorption [see DRUG INTERACTIONS].
Evaluate the need for dose adjustments when regularly administering within one hour of certain foods that may affect LEVOTHYROXINE absorption [see, DRUG INTERACTIONS, CLINICAL PHARMACOLOGY].
Administer LEVOTHYROXINE to infants and children who cannot swallow intact tablets by crushing the tablet, suspending the freshly crushed tablet in a small amount (5 mL to 10 mL or 1 teaspoon to 2 teaspoons) of water and immediately administering the suspension by spoon or dropper. Do not store the suspension. Do not administer in foods that decrease absorption of LEVOTHYROXINE, such as soybeanbased infant formula [see DRUG INTERACTIONS].
General Principles Of Dosing
The dose of LEVOTHYROXINE 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 Dosing In Specific Populations, WARNINGS AND PRECAUTIONS, DRUG INTERACTIONS]. 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 Monitoring TSH And/Or Thyroxine (T4) Levels].
The peak therapeutic effect of a given dose of LEVOTHYROXINE may not be attained for 4 to 6 weeks.
Dosing In Specific Populations
Primary Hypothyroidism In Adults And In Adolescents In Whom Growth And Puberty Are Complete
Start LEVOTHYROXINE 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 LEVOTHYROXINE is approximately 1.6 mcg per kg per day (for example: 100 mcg per day to 125 mcg per day for a 70 kg adult).
Adjust the dose by 12.5 mcg 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 of 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 cardiac disease, start with a dose of 12.5 mcg per day 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 LEVOTHYROXINE 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 mcg per day to 25 mcg per day. Adjust the dose in 12.5 mcg 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 LEVOTHYROXINE at the full replacement dose in otherwise healthy, non-elderly individuals. Start with a lower dose in elderly patients, patients with underlying cardiovascular disease or patients with severe longstanding hypothyroidism as described above. Serum TSH is not a reliable measure of LEVOTHYROXINE dose adequacy in patients with secondary or tertiary hypothyroidism and should not be used to monitor therapy. Use the serum free-T4 (L-thyroxine) level to monitor adequacy of therapy in this patient population. Titrate LEVOTHYROXINE 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
The recommended daily dose of LEVOTHYROXINE in pediatric patients with hypothyroidism is based on body weight and changes with age as described in Table 1. Start LEVOTHYROXINE at the full daily dose in most pediatric patients. Start at a lower starting dose in newborns (0 to 3 months) at risk for cardiac failure and in children at risk for hyperactivity (see below). Monitor for clinical and laboratory response [see Monitoring TSH And/Or Thyroxine (T4) Levels].
Table 1: EUTHROX Dosing Guidelines for Pediatric Hypothyroidism
|AGE||Daily Dose Per Kg Body Weight*|
|0 to 3 months||10 mcg/kg daily to 15 mcg/kg daily|
|3 to 6 months||8 mcg/kg daily to 10 mcg/kg daily|
|6 to 12 months||6 mcg/kg daily to 8 mcg/kg daily|
|1 to 5 years||5 mcg/kg daily to 6 mcg/kg daily|
|6 to 12 years||4 mcg/kg daily to 5 mcg/kg daily|
|Greater than 12 years but growth and puberty incomplete||2 mcg/kg daily to 3 mcg/kg daily|
|Growth and puberty complete||1.6 mcg/kg daily|
|*The dose should be adjusted based on clinical response and laboratory parameters [see Monitoring TSH And/Or Thyroxine (T4) Levels, Use In Specific Populations]|
Newborns (0 to 3 months) At Risk For Cardiac Failure
Consider a lower starting dose in newborns at risk for cardiac failure. Increase the dose 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 in pediatric patients, 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.
LEVOTHYROXINE 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 LEVOTHYROXINE by 12.5 mcg daily to 25 mcg daily and measure TSH every 4 weeks until a stable LEVOTHYROXINE dose is reached and serum TSH is within the normal trimester-specific range. Reduce LEVOTHYROXINE dosage to pre-pregnancy levels immediately after delivery and measure serum TSH levels 4 to 8 weeks postpartum to ensure LEVOTHYROXINE 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 LEVOTHYROXINE at the full replacement dose (1.6 mcg per kg body weight per day). In patients with mild hypothyroidism (TSH less than 10 mIU per liter) start LEVOTHYROXINE at 1 mcg per kg body weight per day. Evaluate serum TSH every 4 weeks and adjust LEVOTHYROXINE dosage until a serum TSH is within the normal trimester-specific range [see Use In Specific Populations].
TSH Suppression In Well-Differentiated Thyroid Cancer
The dose of LEVOTHYROXINE should target TSH levels within the desired therapeutic range. This may require a LEVOTHYROXINE dose of greater than 2 mcg per kg per day, depending on the target level for TSH suppression.
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 LEVOTHYROXINE may be evidence of inadequate absorption, poor compliance, drug interactions, or a combination of these factors.
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.
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 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 dose 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.
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 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 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 LEVOTHYROXINE [see WARNINGS AND PRECAUTIONS and Use In Specific Populations])].
Secondary And Tertiary Hypothyroidism
Monitor serum free-T4 levels and maintain in the upper half of the normal range in these patients.
Store between 20°C to 25°C (68°F to 77°F), with excursions permitted between 15°C to 30°C (59°F to 86°F). Protect from light and moisture, avoid heat. Do not separate the individual cavities containing the tablet from the intact blister and do not remove the individual tablets from blister packaging until ready to use.