NAC
N-Acetylcysteine
Also known as: N-acetyl-L-cysteine, Acetadote
A glutathione precursor that is FDA-approved as a mucolytic and antidote for acetaminophen overdose, and studied more broadly in psychiatry and respiratory health.
Overview
N-acetylcysteine is a well-absorbed precursor of cysteine that supports glutathione synthesis. It is FDA-approved as a mucolytic and, intravenously, as the standard antidote for acetaminophen (paracetamol) overdose, where the evidence is strong. It has also been studied in psychiatry, addiction, and respiratory conditions, with more variable results.
Mechanism of action
Provides cysteine to replenish glutathione, directly scavenges free radicals, and modulates glutamatergic signaling in the brain.
Key studies & citations
- Human1988
Efficacy of oral N-acetylcysteine in the treatment of acetaminophen overdose: analysis of the national multicenter study (1976 to 1985)
In 2,540 treated overdose patients, hepatotoxicity fell to 6.1% when NAC was started within 10 hours; NAC was protective regardless of initial acetaminophen level when given within 8 hours.
New England Journal of Medicine - Human1977
Treatment of paracetamol (acetaminophen) poisoning with N-acetylcysteine
First report of intravenous NAC in 15 poisoned patients: liver function stayed normal or near normal in 11 of 12 treated within 10 hours; established the IV regimen.
The Lancet - Human2025
Acetadote (acetylcysteine) injection: prescribing information
FDA-approved label: IV acetylcysteine given within 8 to 10 hours of a potentially hepatotoxic acetaminophen ingestion to prevent or lessen liver injury; anaphylactoid reactions are the key warning.
U.S. FDA (Drugs@FDA label) - Review2015
Clinical trials of N-acetylcysteine in psychiatry and neurology: a systematic review
Favorable but early evidence in several psychiatric and neurological conditions; larger controlled trials still needed and results vary by indication.
Neuroscience and Biobehavioral Reviews
Frequently asked questions
Is NAC the same as glutathione?
No. NAC is a precursor the body uses to make glutathione, and it is much better absorbed orally than glutathione itself.