21 CFR §207.37

1. (a)A product may be deemed to be misbranded if an NDC is used:
   1. (1)To represent a different drug than the drug for which the NDC has been assigned, as described in § 207.33;
   2. (2)To denote or imply FDA approval of a drug; or
   3. (3)On products that are not subject to parts 207, 607 of this chapter, or 1271 of this chapter, such as dietary supplements and medical devices.
2. (b)If marketing is resumed for a discontinued drug, and no changes have been made to the drug that would require a new NDC under § 207.35, the drug must have the same NDC that was assigned to it as described in § 207.33, before marketing was discontinued.