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Abbott Files NDA, Will Continue to Distribute Synthroid

Kate Traynor

Abbott Laboratories announced August 1 that it had submitted to FDA a new drug application (NDA) for Synthroid, the levothyroxine sodium product acquired by the company when it purchased Knoll Pharmaceutical Co. earlier this year.

Synthroid is the sixth oral levothyroxine sodium product for which an NDA was filed before FDA’s August 14 deadline, according to AJHP inquiries. By meeting the deadline, Abbott retains the right to distribute gradually decreasing amounts of Synthroid until August 14, 2003. If FDA approves the NDA, Abbott may resume normal distribution of its product.

Although oral levothyroxine sodium products have been marketed in the United States for decades, only two compounds, Unithroid by Jerome Stevens Pharmaceuticals and Jones Pharma Inc.’s Levoxyl, have FDA-approved labeling. FDA declared in 1997 that oral levothyroxine sodium products are new drugs for which NDAs must be filed. The August deadline was the last chance for manufacturers of currently marketed levothyroxine products to submit the paperwork that would allow the companies to continue to legally distribute those products in the United States.

Abbott’s filing of an NDA ended a four-year confrontation between FDA and Knoll. During this time, Knoll filed and repeatedly supplemented a citizen’s petition to exempt Synthroid from the NDA process, and FDA extended by one year the cutoff date for manufacturers to submit an NDA.

FDA denied Knoll’s citizen petition on April 26, 2001, about a month after the company was acquired by Abbott.

In addition to Abbott, three other manufacturers—Forest Pharmaceuticals Inc., Qualitest Products Inc., and Vintage Pharmaceuticals Inc.—claim to have met the August 14 deadline. FDA spokeswoman Crystal Rice, citing agency policy, declined to confirm this information.

Rice also declined to estimate how long the reviews of NDAs submitted for levothyroxine products will take but instead noted that "our standard application reviews are running 10–12 months, and priority reviews are running around 6 months."

FDA’s review of the NDAs for Unithroid and Levoxyl took about 10 months. These products, whose applications were approved before FDA’s August 14 deadline, are not affected by the agency’s decision to gradually phase out the distribution of products under review.

But Synthroid and other levothyroxine products with NDAs under review will be affected by the FDA’s phasedown policy. From February through April of next year, FDA will require those products’ manufacturers to decrease their distribution of oral levothyroxine products to 80% of the average amount shipped during February–July 2001. From May through July 2002, if the NDA has still not been approved, the manufacturer must reduce its distribution of the product to 60% of the average amount shipped during February–July 2001.

By August 14, 2003, the phasedown policy requires cessation of the distribution of all unapproved levothyroxine sodium products. Additional information about FDA’s phasedown policy appears in a guidance document.