The following information is obtained from various newswires,
published medical journal articles, and medical conference presentations.
Company: Abbott Laboratories
Approval Status: Approved July 2002
Treatment for: Hypothyroidism and suppression of thyroid-stimulating hormone
General Information
Synthroid has been approved as replacement or supplemental therapy for primary, secondary, tertiary and subclinical hypothyroidism
According to Abbott Laboratories, Synthroid is the number one prescribed treatment for hypothyroidism and the second most-prescribed medication overall in the United States. The formal approval validates the safety and efficacy of the therapy, and it allows physicians to continue prescribing it to patients.
Side Effects
Adverse reactions associated with levothyroxine therapy are usually symptoms of hyperthyroidism due to therapeutic overdosage.
Mechanism of Action
Synthetic levothyroxine (T4) is identical to that produced naturally in the human thyroid gland.
Thyroid hormone synthesis and secretion is regulated by the hypothalamic-pituitarythyroid
axis. Thyrotropin-releasing hormone (TRH) released from the hypothalamus
stimulates secretion of thyroid--stimulating hormone, TSH, from the anterior
pituitary. TSH, in turn, is the physiologic stimulus for the synthesis and secretion of
thyroid hormones, L-thyroxine (T4) and L-triiodothyronine (T3), by the thyroid gland. Circulating serum T3 and T4 levels exert a feedback effect on both TRH and TSH secretion. When serum T3 and T4 levels increase, TRH and TSH secretion decrease. When thyroid hormone levels decrease, TRH and TSH secretion increase. (From Synthroid prescription label)
Additional Information
In July 2001, the FDA announced that it would require all manufacturers of levothyroxine sodium products to submit New Drug Applications for approval of these products. This guidline applies to both original and generic forms of the levothyroxine sodium drugs.
For more information about this FDA ruling, please refer to the guidance itself on the FDA web site at www.fda.gov/cder/guidance/4647fnl.htm.
