Last week, the U.S. Food and Drug Administration (FDA) issued a response denying citizen petition requests from the Natural Products Association (NPA) and the Council for Responsible Nutrition (CRN) calling on the agency to clarify that N-acetyl cysteine (NAC) is a lawful dietary ingredient.

The agency communicated the possibility that, pending further review, it could initiate rulemaking that would permit use of NAC as or in dietary supplements. This rulemaking had been requested as an alternate course of action in the citizen petition by NPA. The agency also stated that it would consider applying a policy of enforcement discretion for otherwise lawful NAC products, and that it intended to issue guidance about its policy on NAC-containing products labeled as dietary supplements in the near future.

Among several other legal arguments discussed in its decision, FDA asserted that section 201(ff)(3)(B) of the FD&C Act (commonly referred to as the prior drug exclusion provision) does not provide an exception for a) drugs that were approved prior to DSHEA, b) drugs that were authorized for investigation prior to DSHEA, or c) dietary supplements or foods that were marketed as such prior to DSHEA. FDA further asserted that this interpretation of the exclusion clause does not give it a retroactive effect because its effects governed future conduct.

AHPA had submitted multiple comments in support of both citizen petitions, including documentation demonstrating that NAC had been lawfully marketed as an ingredient in conventional foods and in dietary supplements prior to October 15, 1994. The full response letter from FDA addressing both petitions can be accessed at this address.