Abbott Laboratories received US Food and Drug Administration (FDA) approval of its synthetic thyroid hormone replacement therapy, Synthroid (levothyroxine sodium tablets, USP), for thyroid disease management, as replacement or supplemental therapy for hypothyroidism (underactive thyroid) and pituitary thyroid stimulating hormone suppression, a company release said.

"Today's FDA approval is good news for the millions of Americans who rely on Synthroid every day to control their thyroid disease," said Jeffrey Leiden, Abbott's chief scientific officer and president, Global Pharmaceuticals. "This approval confirms that Synthroid is safe and effective. Synthroid is the same drug, and patients should continue to take their medication as they always have," he added.

Synthroid is prescribed for hypothyroidism and the second most-prescribed medication overall in the United States.

"Today's FDA approval ensures that patients will continue to have access to this vital medication, which has been relied upon by physicians and patients for almost 50 years," said Paul Ladenson, director of the Division of Endocrinology and Metabolism at Johns Hopkins Medical Institutions.

The FDA publication, Approved Drug Products with Therapeutic Equivalence Evaluations (Orange Book), does not list any levothyroxine sodium products as therapeutically interchangeable with Synthroid. Switching Synthroid patients to another brand of thyroid medication would require testing and retitration, if necessary, the release says.

Synthroid is indicated as replacement or supplemental therapy for primary, secondary, tertiary and subclinical hypothyroidism. Synthroid is not indicated for transient hypothyroidism during recovery of subacute thyroiditis. Thyroid hormones, including Synthroid, either alone or with other therapeutic agents, should not be used for the treatment of obesity or for weight loss. In euthyroid patients, doses within the range of daily hormonal requirements are ineffective for weight reduction.

Millions of patients and their physicians have relied on Synthroid for decades to maintain their thyroid health. Formal approval by FDA of Synthroid validates its safety and efficacy. With FDA approval, Abbott is now free to meet full market demand, the release said.