Once an approved NDA product is discontinued from marketing or withdrawn, the FDA must make a determination that the reason for such action by the innovator was not for safety or efficacy reasons (see 21 CFR 314.161(a)). Such a determination must be made before an ANDA for a duplicate of the reference listed drug (RLD) is approved or if there are approved ANDAs at the time the reference NDA product is withdrawn or discontinued from marketing.
A person may petition the Agency for such a determination or the Agency may, on its own initiative, review its records and make the determination. Today, in the pre-publication of the Federal Register Notice (here), the FDA has issued its determinations that twenty NDA products were not discontinued for reasons of safety or efficacy. Therefore, approved ANDAs for these products can continue to be marketed and new ANDAs can be submitted and approved. It appears from the notice that the FDA has made these decisions on its own initiative.