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August 22, 2000
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FDA today approved the first NDA for the thyroid hormone replacement drug, levothyroxine sodium (Unithroid) for use in adults and children.
In children, thyroid hormones are essential for normal physical growth and intellectual development. They are also involved in the regulation of a wide range of metabolic processes within the body in all age groups. Hypothyroidism, or low levels of thyroid hormone, may be due to a birth defect (e.g. partial or complete absence of the thyroid gland) or it may occur later in life due, for example, to thyroiditis, goiter, or surgical removal of the thyroid gland.
Symptoms of hypothyroidism include poor growth in children and, in those born with this disorder, impaired intellectual development if this disorder is not promptly and adequately treated. Symptoms of hypothyroidism in children and adults include fatigue, cold intolerance, dry skin, lethargy and weight gain.
Levothyroxine is identical to a natural thyroid hormone produced by the body and is most commonly used to return thyroid hormone levels to normal in patients with hypothyroidism. The dose of levothyroxine for replacement or supplemental therapy in patients with hypothyroidism must be individualized based on patient response. Patients taking levothyroxine as replacement must be monitored with blood tests at regular intervals to determine that thyroid hormone levels are within the normal range, to assure patient safety, and to help guide dose adjustments.
During initiation of replacement therapy with levothyroxine, blood tests are usually performed every six to eight weeks in adults to aid in dose adjustment. Once the optimal replacement dose of levothryoxine for an individual adult patient is determined, blood tests are usually done less frequently; e.g., every six to twelve months. Infants and children are usually begun on full levothyroxine replacement doses and the frequency of monitoring of blood tests, growth and intellectual development is age-dependent.
Side effects from levothyroxine are usually due to over-dosage and include nervousness, weight loss, tachycardia (rapid heart beat), irritability, and anxiety.
Although oral levothyroxine drugs products have been marketed in the United States since the 1950's, the approval of Unithroid represents the first time that a single ingredient oral levothryoxine product has been approved by the FDA.
In the August 14, 1997 Federal Register, FDA announced that orally administered drug products containing levothyroxine sodium are new drugs. The unapproved thyroid hormone replacement products that have been on the market have been associated with stability and potency problems. These problems have resulted in product recalls and have the potential to cause serious health consequences to the public.
To address these concerns, the agency announced that after August 14, 2001, any orally administered levothyroxine drug product must be the subject of an approved New Drug Application. If there is no such approved application, the product will be subject to regulatory action as an unapproved new drug. With the approval today of Unithroid, patients and physicians will now have available to them an oral levothryroxine sodium drug product that has been determined to be safe and effective by the FDA and that also meets FDA standards for manufacturing processes, purity, potency, and stability.
Unithroid is manufactured and distributed by Jerome Stevens Pharmaceuticals of Bohemia, NY.
For more information on this topic, see the Center for Drug Evaluation and Research's Unithroid Information Page.