CRN sent a letter this week addressed to Douglas Stern, deputy director for regulatory affairs for the US Food and Drug Administration. In the letter, CRN alleges that FDA’s responses on the NAC issue have dodged a central legal question.
FDA first declared NAC as an illegal dietary ingredient via a series of warning letters to marketers of hangover cures that were posted in July 2020. Several of these products included NAC, which FDA, in a side note in the warning letters, said was not a legal dietary ingredient because of its prior use as a drug. It was the first time the Agency had made that kind of statement about the ingredient.
Ingredient on market for decades, without safety concerns
NAC, or N-acetyl-L-cysteine, is a derivative of the amino acid L-cysteine and is a precursor of the cellular antioxidant glutathione. The ingredient was first approved as a mucolytic drug sometime around 1963. It’s hard to say with certainty if that’s the right date because of imprecise documentation, which has been one of CRN’s objections.
It’s unclear how long it was marketed for that use, but it has not been used a prescription pharmaceutical in many decades. At present it is used in emergency rooms as a treatment in cases of acetaminophen poisoning to prevent severe liver damage. The ingredient has a long history of safety in that application where it is administered at a much higher dosage than what is found in dietary supplements, according to Rick Kingston, PharmD of the University of Minnesota (Kingston is also the president of regulatory and scientific affairs at Safety Call International).