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

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

Talk to your health care provider about which foods, supplements, and medicines you need to avoid. The symptoms of hypothyroidism can be different from person to person. Because of that, a diagnosis of hypothyroidism doesn’t rely on symptoms alone.

Patient Handout

Not all of the concerns about generic levothyroxine have been allayed. For example, if you are taking Synthroid and thinking about switching to save costs, there is evidence that doing so may not be the best idea. As of 2023, the average synthroid retail price of Synthroid 50 mg hovers at around $150 for a 90-day (three-month) supply.

You are encouraged to report negative side effects of prescription drugs to the FDA. The major pathway of thyroid hormone metabolism is through sequential deiodination. Approximately 80% of circulating T3 is derived from peripheral T4 by monodeiodination.

Drugs Known To Affect Thyroid Hormone Pharmacokinetics

In contrast, the average retail price of generic levothyroxine 50 mg is closer to $45 for a 90-day supply. As such, if the early findings were correct, it would suggest that generic levothyroxine works “less well” in managing thyroid disease. 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.

The non-Synthroid formulations considered in the study included Levothroid, Levoxyl, Tirosint, Unithroid, and generic levothyroxine. The post-period was defined as the time from the index date through 2years following the index date. Most health care providers recommend taking the medicine levothyroxine to treat hypothyroidism.

The longer that a generic drug is on the market, the smaller the cost difference will be (due largely to the decreasing price of the brand-name drug). While it is possible to be sensitive to certain inactive ingredients in levothyroxine, like lactose or color additives, the amounts are generally so low as to pose few health risks. Generic levothyroxine products licensed by the FDA are just as safe as Synthroid. There is no evidence of one being “more safe” or “less safe” than another. Seizures have been reported rarely with the institution of levothyroxine therapy.

Assessment of interchangeability of two brands of levothyroxine preparations with a third-generation TSH assay.

Furthermore, the results for all individual comorbidities examined in patients who switched three or more times were statistically significant when compared against continuous use of Synthroid®. Regardless of the number of switches, switchers were also more likely to have TSH levels outside the recommended target range. In sum, these findings support clinical guidelines which advise that patients with hypothyroidism should continue therapy with the same synthetic LT4 formulation and avoid switching among LT4 formulations, when possible 15. Currently, there is no clear, high-level guideline on how to best adjust the starting dosage in patients with a body mass index greater than 30 kg per m2.

• 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.
• However, the emerging findings highlight that the currently accepted range is no longer backed by evidence and the need exists to reevaluate the existing literature.
• If the level is elevated, they will conduct a second test examining Free T4 levels.
• If cardiac symptoms develop or worsen, reduce the SYNTHROID dose or withhold for one week and restart at a lower dose.

Hypothyroidism (underactive thyroid)

While switching between generics may also be OK, the American Thyroid Association recommends staying with one drug rather than switching from one to the next. Whatever form of levothyroxine you use, take it daily as prescribed to ensure the best results. Even so, ongoing concerns about the safety and efficacy of generic levothyroxine have altered the prescribing practices of some healthcare providers. 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.

For secondary or tertiary hypothyroidism, serum TSH is not a reliable measure of SYNTHROID dosage adequacy and should not be used to monitor therapy. Use the serum free-T4 level to titrate SYNTHROID dosing until the patient is clinically euthyroid and the serum free-T4 level is restored to the upper half of the normal range see Recommended Dosage And Titration. Synthroid is prescribed in tablets that range from 25 to 300 mcg in strength and is usually taken once a day with a full glass of water (about 8 ounces) 30 to 60 minutes before breakfast for best adsorption into the body. Children can take the medicine if the tablet is crushed and put into about 1 to 2 teaspoons of water; do not store or delay giving this crushed pill suspension. Doctors often may have to slowly increase the dose; patients should not increase or decrease this medication themselves.

Hypothyroidism, or underactive thyroid, happens when your thyroid gland doesn’t make enough thyroid hormones to meet your body’s needs. Ramon Espaillat, Yinghui Duan and Seema Soni-Brahmbhatt are employees of AbbVie, Inc. and may own shares of AbbVie stock. Maureen J. Lage is Managing Member of HealthMetrics Outcomes Research, LLC which was compensated for work on this project. James V. Hennessey has previously served as an academic consultant to AbbVie, developing educational material in regard to thyroid hormone bioequivalence issues, technical regulatory filing advise and other clinical study designs. He has received no compensation for his contributions to this project. Peter Singer has previously served as consultant to AbbVie, Inc. and reports no conflicts on this research.