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- What is levothyroxine sodium, and how does it work (mechanism of action)?
- What brand names are available for levothyroxine sodium?
- Is levothyroxine sodium available as a generic drug?
- Do I need a prescription for levothyroxine sodium?
- What are the side effects of levothyroxine sodium?
- What is the dosage for levothyroxine sodium?
- Which drugs or supplements interact with levothyroxine sodium?
- Is levothyroxine sodium safe to take if I'm pregnant or breastfeeding?
- What else should I know about levothyroxine sodium?
What is levothyroxine sodium, and how does it work (mechanism of action)?
Levothyroxine is a synthetic (man-made) version of the principle thyroid hormone, thyroxine (T4) that is made and released by the thyroid gland. Thyroid hormone increases the metabolic rate of cells of all tissues in the body. In the fetus and newborn, thyroid hormone is important for the growth and development of all tissues including bones and the brain. In adults, thyroid hormone helps to maintain brain function, utilization of food, and body temperature, among other effects.
What brand names are available for levothyroxine sodium?
Synthroid, Levoxyl, Levothroid, Unithroid, Tirosint, Levo-T (discontinued brand)
Is levothyroxine sodium available as a generic drug?
GENERIC AVAILABLE: Yes. Generic and branded tablets of levothyroxine may differ:
- in the amount of levothyroxine they contain,
- the absorption of the levothyroxine into the body, and
- the distribution of levothyroxine throughout the body.
This means that ingestion of 1 mg of generic levothyroxine may not have the same effect on the body as 1 mg of another generic or branded levothyroxine. Practically speaking, this means that when changing between levothyroxine manufactured by different pharmaceutical companies, a change in dose may be necessary to maintain the desired effect or to prevent toxicity. When switching between brands or generics, it is important to ensure that both preparations are equivalent or to check blood thyroid levels weekly.
Do I need a prescription for levothyroxine sodium?
What are the side effects of levothyroxine sodium?
Levothyroxine therapy usually is well-tolerated. If symptoms occur, they often are due to toxic levels of thyroid hormone, and the symptoms are those of hyperthyroidism.
The most commonly reported side effects include:
- chest pain,
- increased heart rate or pulse rate,
- excessive sweating,
- heat intolerance,
- weight loss, or
- Women may experience irregular menstrual cycles.
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
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