NAC

N-acetylcysteine (NAC) is a medication and dietary supplement that is a derivative of the amino acid cysteine. It is a thiol-containing compound that acts as a precursor to the antioxidant glutathione, helping to restore cellular redox balance.

NAC is best known in medicine as an antidote for acetaminophen (paracetamol) overdose, where it replenishes hepatic glutathione stores and mitigates liver injury. It is also used as a mucolytic agent to decrease mucus viscosity in certain respiratory conditions, such as chronic bronchitis and cystic fibrosis, to aid mucus clearance.

The primary mechanism involves replenishing glutathione, which conjugates toxic metabolites like NAPQI in acetaminophen poisoning. The mucolytic effect arises from disruption of disulfide bonds in mucus, reducing thickness and facilitating expectoration.

Administration and forms vary by indication. NAC is available in oral and intravenous formulations. For overdose treatment, intravenous NAC is given under medical supervision according to a protocol; oral regimens exist when IV administration is not feasible. Dosing and duration depend on the specific use and product formulation.

Safety considerations include that NAC is generally well tolerated. Common adverse effects are nausea, vomiting, and diarrhea; intravenous use can be associated with flushing, rash, pruritus, or rare anaphylactoid reactions. Serious adverse events are uncommon but may occur, necessitating medical monitoring during administration.

Regulatory status varies by country. NAC is approved for acetaminophen poisoning in many jurisdictions and marketed as a mucolytic in others; in some markets it is available as a dietary supplement with variable quality control and labeling.