The world’s largest e-commerce platform is resuming the sale of NAC-containing dietary supplements after FDA published final guidance about the ingredient.

A representative for one of the nation’s most prominent supplement companies, NOW Health Group, said the company has been “quietly notified” it may resume sales of NAC (N-acetyl-L-cysteine) on Amazon’s platform.

“NOW is in the process of resuming sales of NAC on Amazon,” Dan Richard, vice president of global sales and marketing with NOW Health Group, said in an email to Natural Products Insider.

NutraIngredients-USA first reported Thursday on the development, citing Richard.

Separately Thursday, Natural Products Insider confirmed directly with Amazon that the company has updated its policies to reflect FDA’s NAC final guidance. A search of "NAC supplements" on Amazon's website yields myriad brands for sale. 

As Natural Products Insider exclusively reported, Amazon confirmed in spring of 2021 it was removing NAC supplements from its platform after FDA asserted the ingredient could not be marketed as a dietary supplement since it was first approved as a drug.

But in final guidance published earlier this month, FDA announced its plans “to exercise enforcement discretion” regarding the distribution and sale of certain NAC-containing products labeled as dietary supplements.

FDA’s “enforcement discretion policy applies to products that would be lawfully marketed dietary supplements if NAC were not excluded from the definition of ‘dietary supplement’ and that are not otherwise in violation of the FD&C [Federal Food, Drug & Cosmetic] Act,” according to the final guidance.

Amazon’s guidelines on dietary supplements list certain ingredients and products that cannot be sold, including cannabidiol (CBD)—another ingredient that FDA says is excluded from the definition of a dietary supplement because it was first studied as a drug—but they do not reference NAC.

‘Very significant’

The resumption of NAC sales on Amazon is “very significant,” according to Natural Products Association (NPA) President and CEO Dan Fabricant.

In an interview, he said Amazon’s removal of NAC supplements from its platform caused a loss of “millions, if not tens of millions of dollars” in sales for supplement brands, and it was one of the reasons NPA filed a citizen petition with FDA and sued the agency regarding its position.

NPA’s lawsuit against FDA remains pending in U.S. District Court in Maryland.

“FDA caused economic harm,” Fabricant said.

United Natural Products Alliance (UNPA) President Loren Israelsen described this week’s development as “welcome news.”

Industry stakeholders provided evidence to FDA that NAC was marketed safely in nutritional products since the 1990s, but FDA concluded it was prohibited from dietary supplements under the FD&C Act since it had been first approved as a drug in 1963.

“The fact that NAC's safety is not in question does add a somber note to this story,” Israelsen said via email. “While we understand Amazon's need to closely manage real or perceived risks, we lament that it ever came to this.”

In comments filed with FDA in response to a draft guidance, many consumers had advocated to keep NAC available in products labeled as dietary supplements.

“NAC has demonstrated a multitude of beneficial effects based on oral administration,” George LeBaron wrote to FDA. “Most notable is its ability to help support glutathione levels and subsequently attenuate normal oxidative stress.”

The tug-of-war between industry and FDA over NAC reflected disagreements over interpretation of a provision in federal law that prohibits ingredients from being marketed in dietary supplements if they were first studied or approved as a drug.

Trade associations made several legal arguments in citizen petitions that FDA’s position regarding NAC was incorrect. FDA disagreed in a comprehensive response to the petitions, but the final guidance on enforcement discretion grants industry some breathing room to sell NAC in dietary supplements without fear of adverse regulatory consequences. FDA also is considering whether to initiate a formal rulemaking to make NAC lawful in supplements despite the ingredient's earlier drug approval.

“Increasingly, the exclusion rule (race to market between drugs and dietary supplements) is becoming a more complex problem,” Israelsen observed. “NAC was caught in the middle, where safety did not count, dates on the calendar did. Going forward, I think we will be spending much more time fighting to preserve new uses for old substances coming back into public and scientific interest.”

Megan Olsen, senior vice president and general counsel with the Council for Responsible Nutrition (CRN), said her organization has been in touch with Amazon regarding NAC since it learned the company was removing NAC products from its platform. CRN last year also had filed a citizen petition with FDA regarding NAC.

“We immediately notified Amazon of FDA’s enforcement discretion—both the draft and final guidance and had conversations with Amazon about updating their policy to allow NAC supplements that complied with the FDA’s policy,” Olsen said in an email. “We are pleased to confirm with our members that companies are able to put NAC supplement products back on Amazon’s platform and that Amazon is recognizing the FDA actions allowing for the continued sale of this beneficial supplement.”