N-Acetylcysteine (NAC)
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In plain English
N-acetylcysteine (NAC) is a versatile medicine and supplement. It thins mucus (helping clear airways), is the antidote for acetaminophen (Tylenol) overdose, and acts as an antioxidant. As eye drops it is used for dry-eye/ocular surface conditions to break down sticky mucus. It is generally safe and well tolerated.
The science
NAC is a precursor of cysteine and glutathione that hydrolyzes disulfide bonds in mucus glycoproteins to reduce viscosity, and it replenishes hepatic glutathione to detoxify the reactive acetaminophen metabolite NAPQI. It is FDA-approved as a mucolytic and for acetaminophen toxicity (nearly 100% effective within 8 hours of ingestion), with additional antioxidant and anti-inflammatory activity being studied across many off-label uses.
References
- Tenório MCDS et al. / Schwalfenberg — Acetylcysteine, StatPearls (NCBI Bookshelf) 2023
- Nasir B et al., Mucolytic Medications, StatPearls (NCBI Bookshelf) 2023