January 2021

N-Acetyl Cysteine: Supplement, Drug, or Both?

Updated September 2022

N-acetyl cysteine (NAC) comes from the amino acid L-cysteine. It’s been available in dietary supplements for decades. But now the FDA is warning companies that it cannot be legally included in supplements. The tug of war between the industry and FDA is confusing, and highlights the great differences in supplement and drug regulations.

NAC was first approved by the FDA as a respiratory drug in 1963. It’s also used to prevent serious liver damage from acetaminophen poisoning. But it’s been available in dietary supplement products for decades – the ingredient itself is likely safe for most people. The FDA has pushed back on the use of NAC in supplements since 2010, but it’s ramped up significantly this year. Some speculate this is due to new clinical investigations into the use of NAC for COVID-19. The FDA claims that there’s no evidence that NAC was used as a supplement prior to its use as a drug – so including NAC in a supplement makes the product an unapproved drug and thus illegal.

In 2021, several dietary supplement companies received warning letters for making hangover treatment claims about their products. The main purpose of these letters was to inform them that making these claims was a violation of the Dietary Supplement Health and Education Act (DSHEA). But in addition to this violation, the FDA also flagged several of these companies for including NAC in their products.

This renewed confusion over the legality of NAC places a spotlight on major holes in supplement regulations. For NAC, and other ingredients with confusing legality like CBD, nothing is black and white. Unlike drugs, there is NO approval process for dietary supplements. If a supplement contains dietary ingredients that were either already used in supplements before DSHEA (1994), or established as reasonably safe since then, it can be lawfully sold to consumers. This is very different from drugs, which must go through an extensive approval process BEFORE entering the market. Those in the dietary supplement industry claim that there is no reason for the FDA to take retroactive steps to remove products that have been available for years with no clear safety issues. They are also concerned that this could open the door for the FDA to make the same determination about other products, such as fish oil and vitamin K.

As of August 2022, the FDA has started to back away from its hard stance, stating that it’s considering a rule to allow the sale of NAC as a dietary supplement. Until the final ruling is made, the FDA intends to practice enforcement discretion for NAC dietary supplement products, as long as safety concerns aren’t identified. Additionally, NAC products pulled from Amazon are once again available for purchase. Stay tuned. We’ll update you as we learn more.

Related topics:

The information in this brief report is intended for informational purposes only, and is meant to help users better understand health concerns. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions. Copyright © 2024 NatMed. Commercial distribution or reproduction prohibited. NatMed is the leading provider of high-quality, evidence-based, clinically-relevant information on natural medicine, dietary supplements, herbs, vitamins, minerals, functional foods, diets, complementary practices, CAM modalities, exercises and medical conditions. Monograph sections include interactions with herbs, drugs, foods and labs, contraindications, depletions, dosing, toxicology, adverse effects, pregnancy and lactation data, synonyms, safety and effectiveness.