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Confusion Over Levothyroxine Settled

Jennifer C. Murphy

Having approved the paperwork for two oral levothyroxine sodium products, FDA announced yesterday how it plans to phase out or stop the distribution of the products still lacking an approved new drug application (NDA).

FDA has cleared the distribution of Unithroid, by Jerome Stevens Pharmaceutical Inc., and Levoxyl, by Jones Pharma. Also, the agency has designated Unithroid as the reference product for abbreviated NDAs of oral levothyroxine sodium products. There are, however, unapproved oral levothyroxine sodium products being used to treat thyroid disorders in the United States.

FDA published a guidance document for the manufacturers of unapproved levothyroxine products to follow in order to remain in compliance with federal regulations.

As of August 14, the distribution of all unapproved levothyroxine products from manufacturers that have not submitted an NDA should cease, according to the FDA. This advice is in line with the agency’s responsibility, since passage of the 1962 Kefauver-Harris Drug Amendments, to ensure that all drug products marketed in the United States are both safe and effective. Oral levothyroxine products first entered the U.S. marketplace before proof of efficacy had to be provided by manufacturers.

FDA’s guidance allows for one exception: manufacturers that have filed an NDA by the August 14 deadline may continue to distribute their product. While FDA reviews the NDA, the manufacturer should distribute its drug product in incrementally decreasing amounts. If the NDA is not approved by August 14, 2003, all distribution must cease.

The allowance of a gradual phasing out of the distribution of unapproved levothyroxine products stems from a 1997 announcement in the Federal Register. FDA stated that it considered oral levothyroxine sodium drug products to be new drugs but also recognized the lack of alternative agents for treating hypothyroidism. The agency wanted to give manufacturers time to conduct the necessary bioavailability and stability studies and obtain approval of the NDA.

As of yesterday, Abbott Laboratories had not submitted an NDA for Synthroid, which the company has produced since acquiring Knoll Pharmaceutical Company in March. According to Abbott, Synthroid is used by 8 million people in this country and has been safely used for 42 years without FDA’s approval of an NDA.

In order to adhere to federal regulation, any manufacturer of an unapproved oral levothyroxine product with an NDA under review must reduce its average monthly distribution of the product and submit quarterly reports to FDA until the NDA has been approved.

As part of the guidance, FDA suggested that patients and health care providers start converting levothyroxine therapies to the appropriate approved product. The agency said the conversions can be done as part of routine medical visits.