Understanding Possible Side Effects

Use this section to review the cases of Steve, Jennifer, and Diana to see how to effectively manage their hypothyroidism with SYNTHROID (levothyroxine sodium). Levothyroxine toxicity is rare, but it can sometimes occur accidentally, especially in children. If someone takes too much levothyroxine, symptoms might not occur for several days. Symptoms of levothyroxine overdose include irregular heartbeat, headache, anxiety, agitation, shaking, fatigue, confusion, and disorientation. Certain foods and medications can interfere with the absorption of levothyroxine.

Does Synthroid interact with my other drugs?

The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. 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. Biotin supplementation is known to interfere with thyroid hormone immunoassays that are based on a biotin and streptavidin interaction, which may result in erroneous thyroid hormone test results. Stop biotin and biotin-containing supplements for at least 2 days prior to thyroid testing.

Synthroid During Pregnancy and Breastfeeding

Common brand names of levothyroxine in the US include Synthroid, Levoxyl, Unithroid, and Tirosint. A study evaluated the effect of long-term thyroid hormone therapy on bone mineral density in 196 women (mean age, 74.4 years) compared to a control group comprised of 795 women (mean age, 72.1 years). The mean daily thyroxine dose was 1.99 mcg/kg (range, 0.3 to 6.6 mcg/kg) with a mean duration of therapy of 20.4 years (range, less than 1 to 68 years).

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. 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 Important Considerations For Dosing. Myxedema coma is a life-threatening emergency characterized by poor circulation and hypometabolism and may result in unpredictable absorption of levothyroxine sodium from the gastrointestinal tract. Use of oral thyroid hormone drug products is not recommended to treat myxedema coma.

Toxic effects may include increased risk of cardiac arrhythmias and central nervous system stimulation. Administration of sertraline in patients stabilized on SYNTHROID may result in increased SYNTHROID requirements. TSH may not normalize in some patients due to in utero hypothyroidism causing a resetting of pituitary-thyroid feedback. 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.

Pregnant and lactating females need to discuss the dose and use of this medication with their caregivers. This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

• However, estrogen use appeared to negate the adverse effects of thyroid hormone on bone mineral density.
• Therefore, a decrease in the dose of anticoagulant may be warranted with correction of the hypothyroid state or when the SYNTHROID dose is increased.
• Certain other medicines may also increase or decrease the effects of Synthroid.
• Converting hypothyroidism to the euthyroid state with Synthroid may increase the blood level of theophylline, and it may be necessary to change the dose of theophylline.
• All pregnancies have a background risk of birth defect, loss, or other adverse outcomes.

• Myxedema coma is a life-threatening emergency characterized by poor circulation and hypometabolism and may result in unpredictable absorption of levothyroxine sodium from the gastrointestinal tract.
• They can switch you to a different type of generic or tell the pharmacy you need to be on the brand name.
• Protein-bound thyroid hormones exist in reverse equilibrium with small amounts of free hormone.
• "Taking Synthroid replaces the hormones that your thyroid should be making but, for whatever reason, isn't."
• Tell your doctor if you have an untreated or uncontrolled adrenal gland disorder, a thyroid disorder called thyrotoxicosis, or if you have any recent or current symptoms of a heart attack.
• These include urticaria, pruritus, skin rash, flushing, angioedema, various gastrointestinal symptoms (abdominal pain, nausea, vomiting and diarrhea), fever, arthralgia, serum sickness, and wheezing.

These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Serum TSH levels should be monitored and the SYNTHROID dosage adjusted during pregnancy. Since postpartum TSH levels are similar to preconception synthroid bursitis values, the SYNTHROID dosage should return to the pre-pregnancy dose immediately after delivery see DOSAGE AND ADMINISTRATION. 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.

¿Cuál es la información más importante que debo saber sobre levothyroxine?

The recommended daily dosage of SYNTHROID in pregnant patients is described in Table 3. Certain side effects can occur with Synthroid, and these are often the result of your bodygetting too much medicine, also known as overtreatment. So it’s important to talk with yourdoctor about any symptoms you’re experiencing. Synthroid is a thyroid medicine that replaces a hormone normally produced by your thyroid gland to regulate the body's energy and metabolism. SYNTHROID 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 SYNTHROID may induce hyperthyroidism.

Levothyroxine is an oral medication used to treat underactive thyroid gland activity (hypothyroidism). The thyroid is a major gland in the body that is involved in important functions such as metabolism, growth, development, and regulation of body temperature. Levothyroxine is a synthetic version of the main hormone of the thyroid gland, known as thyroxine (T4). In patients who have an underactive thyroid, there is not enough production of thyroid hormones and levothyroxine is prescribed to help maintain normal thyroid hormone function.

Because some preparations of the drug may contain iodine or lactose, patients should tell their doctors about such allergies or reactions to these components. Circulating thyroid hormones are greater than 99% bound to plasma proteins, including thyroxine-binding globulin (TBG), thyroxine-binding prealbumin (TBPA), and albumin (TBA), whose capacities and affinities vary for each hormone. The higher affinity of both TBG and TBPA for T4 partially explains the higher serum levels, slower metabolic clearance, and longer half-life of T4 compared to T3.