GENERIC NAME: levothyroxine sodium
BRAND NAME: Synthroid, Levoxyl, Levothroid, Unithroid, Tirosint, Levo-T (discontinued brand)
DRUG CLASS AND MECHANISM: 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.
PRESCRIBED FOR: Levothyroxine is approved to treat hypothyroidism to suppress thyroid hormone release from cancerous thyroid nodules, and to prevent growth of goiters. In addition, Synthroid, Levoxyl and Levothyroid also are prescribed with anti-thyroid drugs, for example methimazole (Tapazole), to manage thyrotoxicosis (high thyroid hormone levels due to over-activity of the thyroid gland). Thyrotoxicosis may result in the growth of goiters and/or result in hypothyroidism.
SIDE EFFECTS: 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.
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