SYNTHROID®levothyroxine sodium tablets, USP
Consumption of certain foods may affect SYNTHROID absorption thereby necessitating adjustments in dosing see DOSAGE AND ADMINISTRATION. Soybean flour, cottonseed meal, walnuts, and dietary fiber may bind and decrease the absorption of SYNTHROID from the gastrointestinal tract. Grapefruit juice may delay the absorption of levothyroxine and reduce its bioavailability. Do not administer in celebrex synthroid foods that decrease absorption of SYNTHROID, such as soybean-based infant formula see DRUG INTERACTIONS. Many drugs can inhibit Synthroid’s adsorption by the body; other medications may increase or decrease its effectiveness once it is adsorbed. Providing a complete list of medications to the doctor will help with getting the correct dose established for each individual patient.
Use In Specific Populations
Administration of sertraline in patients stabilized on SYNTHROID may result in increased SYNTHROID requirements. SYNTHROID may reduce the therapeutic effects of digitalis glycosides. Serum digitalis glycoside levels may decrease when a hypothyroid patient becomes euthyroid, necessitating an increase in the dose of digitalis glycosides. There are certain populations where we pay closer attention to thyroid medication dosing. Another group is those that have underlying cardiac disease or are at risk for atrial fibrillation.
Therefore, the dose of SYNTHROID used for TSH suppression should be individualized based on the specific disease and the patient being treated. SYNTHROID is administered as a single daily dose, preferably one-half to one-hour before breakfast. SYNTHROID should be taken at least 4 hours apart from drugs that are known to interfere with its absorption (see PRECAUTIONS – Drug Interactions). You are encouraged to report negative side effects of prescription drugs to the FDA. The estimated background risk of major birth defects and miscarriage for the indicated population is unknown.
Patients with Nontoxic Diffuse Goiter or Nodular Thyroid Disease
SYNTHROID should not be used to treat noncancerous growths or enlargement of the thyroid in patients with normal iodine levels, or in cases of temporary hypothyroidism caused by inflammation of the thyroid gland (thyroiditis). Thyroid hormones, including SYNTHROID, 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.
Overtreatment may result in craniosynostosis in infants and premature closure of the epiphyses in children with resultant compromised adult height. The major pathway of thyroid hormone metabolism is through sequential deiodination. Approximately 80% of circulating T3 is derived from peripheral T4 by monodeiodination. The liver is the major site of degradation for both T4 and T3, with T4 deiodination also occurring at a number of additional sites, including the kidney and other tissues. Approximately 80% of the daily dose of T4 is deiodinated to yield equal amounts of T3 and reverse T3 (rT3). Thyroid hormones are also metabolized via conjugation with glucuronides and sulfates and excreted directly into the bile and gut where they undergo enterohepatic recirculation.
It is recommended that a physical examination and a serum TSH measurement be performed at least annually in patients receiving SYNTHROID (see WARNINGS, PRECAUTIONS, and DOSAGE AND ADMINISTRATION). The adequacy of therapy is determined by periodic assessment of appropriate laboratory tests and clinical evaluation. SYNTHROID® (levothyroxine sodium) tablets, for oral use is a prescription, man-made thyroid hormone that is used to treat a condition called hypothyroidism in adults and children, including infants. It is meant to replace a hormone that is usually made by your thyroid gland.
- Measure and evaluate unbound (free) hormone and/or determine the free-T4 index (FT4I) in this circumstance.
- 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.
- Absorption of orally administered T4 from the gastrointestinal (GI) tract ranges from 40% to 80%.
- It replaces the amount of hormone the thyroid is unable to or can no longer make, helping to restore your thyroid hormone levels to the range they need to be.
TSH Suppression in Well-differentiated Thyroid Cancer and Thyroid Nodules
- 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.
- In addition to testing TSH, sometimes it may be important to run other labs such as a free T4, in addition to the TSH, to ensure you have accurate dosing in the medication.
- Caution should be exercised when administering SYNTHROID to patients with underlying cardiovascular disease, to the elderly, and to those with concomitant adrenal insufficiency (see PRECAUTIONS ).
- 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.
- SYNTHROID is contraindicated in patients with hypersensitivity to any of the inactive ingredients in SYNTHROID tablets (See DESCRIPTION – Inactive Ingredients ).
L-Thyroxine is an amino acid that is one of two hormones located in the thyroid gland; the other is triiodothyronine1. Under the name levothyroxine, it is also a manufactured drug used to treat hypothyroidism. The molecule’s enantiomer, D-thyroxine, has no pharmacological activity. Thyroid hormones exert their physiologic actions through control of DNA transcription and protein synthesis. Triiodothyronine (T3) and L-thyroxine (T4) diffuse 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.
Many other medicines can be affected by your thyroid hormone levels. Certain other medicines may also increase or decrease the effects of Synthroid. The signs and symptoms of overdosage are those of hyperthyroidism (see PRECAUTIONS and ADVERSE REACTIONS). Seizures have occurred in a child ingesting 18 mg of levothyroxine.
The relative bioavailability of SYNTHROID tablets, compared to an equal nominal dose of oral levothyroxine sodium solution, is approximately 93%. T4 absorption is increased by fasting, and decreased in malabsorption syndromes and by certain foods such as soybean infant formula. In addition, many drugs and foods affect T4 absorption (see PRECAUTIONS – Drug Interactions and Drug-Food Interactions ).
Treatment of Overdosage
NP Thyroid is used for hashimoto’s disease, hypothyroidism, after thyroid removal, thyroid cancer … Euthyrox (levothyroxine) is used to treat hypothyroidism and to treat or prevent goiter. It may take several weeks before your body starts to respond to Synthroid. During the first 2 weeks of SYNTHROID therapy, infants should be closely monitored for cardiac overload, arrhythmias, and aspiration from avid suckling. The diagnosis of hypothyroidism is confirmed by measuring TSH levels using a sensitive assay (second generation assay sensitivity ≤ 0.1 mIU/L or third generation assay sensitivity ≤ 0.01 mIU/L) and measurement of free-T4. The thyroid is a small butterfly-shaped gland located at the base of the neck, just below the Adam’s apple.