Synthroid Levothyroxine Sodium: Side Effects, Uses, Dosage, Interactions, Warnings

Follow your doctor’s dosing instructions and try to take the medicine at the same time each day. Follow all directions on your prescription label and read all medication guides or instruction sheets.

Long-term carcinogenicity studies in animals to evaluate the carcinogenic potential of levothyroxine have not been performed. Studies to evaluate mutagenic potential and animal fertility have not been performed. If cardiac symptoms develop or worsen, reduce the SYNTHROID dose or withhold for one week and restart at a lower dose. Concurrent use of ketamine and SYNTHROID may produce marked hypertension and tachycardia.

Report Problems to the Food and Drug Administration

• Biotin supplementation may interfere with immunoassays for TSH, T4, and T3, resulting in erroneous thyroid hormone test results.
• Start at a lower starting dosage and increase the dosage every 4 to 6 weeks as needed based on clinical and laboratory response.
• Synthroid is a prescription medicine used to treat hypothyroidism (low thyroid hormone).

Stop biotin and biotin-containing supplements for at least 2 days before assessing TSH and/or T4 levels see Drug Interactions (7.10). Since postpartum TSH levels are similar to preconception values, the SYNTHROID dosage should return to the pre-pregnancy dose immediately after delivery see DOSAGE AND ADMINISTRATION. Titrate the dose of SYNTHROID carefully and monitor response to titration to avoid these effects see DOSAGE AND ADMINISTRATION. Consider the potential for food or drug interactions and adjust the administration or dosage of SYNTHROID as needed see DOSAGE AND ADMINISTRATION, DRUG INTERACTIONS and CLINICAL PHARMACOLOGY. 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.

If this SPL contains inactivated NDCs listed by the FDA initiated compliance action, they will be specified as such.

If so, advise them to stop biotin supplementation at least 2 days before assessing TSH and/or T4 levels see Dosage and Administration (2.4) and Drug Interactions (7.10). 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).

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 see Dosage and Administration (2.2). 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.

The “80 mcg” part means that each dose of the medication contains 80 micrograms of the active ingredient. “Daily” indicates that the medication should be taken once every day. ​Biotin supplementation may interfere with immunoassays for TSH, T4, and T3, resulting in erroneous thyroid hormone test results.

These include urticaria, pruritus, skin rash, flushing, angioedema, various gastrointestinal symptoms (abdominal pain, nausea, vomiting and diarrhea), fever, arthralgia, serum sickness, and wheezing. Pseudotumor cerebri and slipped capital femoral epiphysis have been reported in pediatric patients receiving levothyroxine therapy. Many other medicines can be affected by your thyroid hormone levels. Certain other medicines may also increase or decrease the effects of Synthroid. Serum TSH levels should be monitored and the SYNTHROID dosage adjusted during pregnancy.

Patient Handout

Dangerous side effects or death can occur from the misuse of levothyroxine, especially if you are taking any other weight-loss medications or appetite suppressants. The physiological actions of thyroid hormones are produced predominantly by T3, the majority of which (approximately 80%) is derived from T4 by deiodination in peripheral tissues. 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.

Assess compliance, dose of medication administered, and method of administration prior to increasing the dose of SYNTHROID see WARNINGS AND PRECAUTIONS and Use In Specific Populations. Assess compliance, dose of medication administered, and method of administration prior to increasing the dose of SYNTHROID. SYNTHROID is indicated in adult and pediatric patients, including neonates, as a replacement therapy in primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) congenital or acquired hypothyroidism. HypothyroidismSYNTHROID® (levothyroxine sodium) tablets, for oral use is indicated as a replacement therapy in primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) congenital or acquired hypothyroidism.

Get medical help right away, if you have any of the symptoms listed above. Administer dexamethasone synthroid SYNTHROID as a single daily dose, on an empty stomach, one-half to one hour before breakfast. Do not share this medicine with another person, even if they have the same symptoms you have. Synthroid works best if you take it on an empty stomach, 30 to 60 minutes before breakfast.