Synthroid Uses, Dosage & Side Effects

SYNTHROID is indicated in adult and pediatric patients, including neonates, as an adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer. Once the patient and I have decided that thyroid hormone replacement is necessary, we go over the specific reasons for choosing and writing Synthroid as that replacement therapy. I review with the patients the important issues about how to take the medication, as consistency is really the key message. I talk about the fact that it’s important to take the medication in the same timing and pattern each day, take it on an empty stomach minutes before they eat. I also review the safety and risks of taking thyroid medication. Published studies report that levothyroxine is present in human milk following the administration of oral levothyroxine.

• A levothyroxine product that is not therapeutically equivalent with SYNTHROID might not have the exact same effect on the patient’s TSH as SYNTHROID.
• Knowing that patient behaviors and consistency of treatment are key factors in treatment success, I educate patients on the process as they begin treatment.
• So, my job as a thyroid specialist in these patients is to make sure my patient is treated and gets to a point of consistency, because it is a lifelong course of medication.

Initiation of thyroid hormone therapy prior to initiating glucocorticoid therapy may precipitate an acute adrenal crisis in patients with adrenal insufficiency. Treat patients with adrenal insufficiency with replacement glucocorticoids prior to initiating treatment with SYNTHROID see CONTRAINDICATIONS. Titrate the dose of SYNTHROID carefully and monitor response to titration to avoid these effects see DOSAGE AND ADMINISTRATION.

ABBVIE IS COMMITTED TO

You are encouraged to report negative side effects of prescription drugs to the FDA. Oral levothyroxine sodium is a synthetic T4 hormone that exerts the same physiologic effect as endogenous T4, thereby maintaining normal T4 levels when a deficiency is present. Consider changes in TBG concentration when interpreting T4 and T3 values.

Synthroid should not be used to treat obesity or weight problems. 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 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.

Adverse Reactions

Measure and evaluate unbound (free) hormone and/or determine the free-T4 index (FT4I) in this circumstance. Pregnancy, infectious hepatitis, estrogens, estrogen-containing oral contraceptives, and acute intermittent porphyria increase TBG concentration. Nephrosis, severe hypoproteinemia, severe liver disease, acromegaly, androgens, and corticosteroids decrease TBG concentration. Familial hyper- or hypo-thyroxine binding globulinemias have been described, with the incidence of TBG deficiency approximating 1 in 9000.

Synthroid During Pregnancy and Breastfeeding

• By visiting Synthroid.com, patients can access additional support and resources to understand and manage their hypothyroidism.
• TSH lower limit of quantification was 0.2 mIU/L and upper limit of normal was 5.6 mIU/L, as indicated by the shaded area.
• Hypersensitivity to levothyroxine itself is not known to occur.
• There are certain foods that can interfere with the way SYNTHROID works, particularly we think about high-fiber foods that can interact with the absorption of thyroid medications.

Serum digitalis glycoside levels may decrease when a hypothyroid patient becomes euthyroid, necessitating an increase in the dose of digitalis glycosides. 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. The importance of writing “Dispense as Written,” or using the state-specific language for SYNTHROID, is something I discuss with my staff as well. This is important as 32% of patients who think they are on SYNTHROID are actually not given this because substitutions are made at the pharmacy. 54% of prescriptions for SYNTHROID were not protected with a DAW or state-specific language in one study.

Serious Risks Related To Overtreatment Or Undertreatment With SYNTHROID

For pregnant patients with pre-existing hypothyroidism, measure serum TSH and free-T4 as soon as pregnancy is confirmed and, at minimum, during each trimester of pregnancy. In pregnant patients with primary hypothyroidism, maintain serum TSH in the trimester-specific reference range. For adult patients with primary hypothyroidism, titrate until the patient is clinically euthyroid and the serum TSH returns to normal see Recommended Dosage And Titration.

Reduce the SYNTHROID dosage or discontinue temporarily if signs or symptoms of overdosage occur. Initiate appropriate supportive treatment as dictated by the patient’s medical status. Start at a lower starting dosage and increase the dosage every 4 to 6 weeks as needed based on clinical and laboratory response. By visiting Synthroid.com, patients can access additional support and resources to understand and manage their hypothyroidism. The FDA has determined that drugs that are classified as therapeutically equivalent can be substituted with the full expectation that the substituted product will produce the same clinical effect and safety profile as the reference product. And to adjust the dose based on periodic assessment of the patient’s clinical response and their laboratory values.

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. Concurrent use synthroid humidity of tyrosine-kinase inhibitors such as imatinib may cause hypothyroidism. Monitor serum free-T4 levels and maintain in the upper half of the normal range in these patients.

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. Protein-bound thyroid hormones exist in reverse equilibrium with small amounts of free hormone. Many drugs and physiologic conditions affect the binding of thyroid hormones to serum proteins see DRUG INTERACTIONS. Thyroid hormones do not readily cross the placental barrier see Use In Specific Populations. Because of the increased prevalence of cardiovascular disease among the elderly, initiate SYNTHROID at less than the full replacement dose see DOSAGE AND ADMINISTRATION and WARNINGS AND PRECAUTIONS.