Nacetilcisztein

N-acetylcysteine, commonly abbreviated as NAC, is a medication and supplement derived from the amino acid cysteine. It contains a thiol group that gives it both mucolytic and antioxidant properties. In the body, NAC is deacetylated to cysteine, a precursor for glutathione synthesis, thereby helping replenish intracellular glutathione stores and support cellular defense against oxidative stress and toxic metabolites.

NAC has two main clinical roles. It is the antidote for acetaminophen (paracetamol) overdose, where it replenishes hepatic glutathione and facilitates detoxification of the reactive metabolite N-acetyl-p-benzoquinone imine (NAPQI). Early treatment improves outcomes, and regimens may be oral or intravenous. NAC is also used as a mucolytic agent in respiratory diseases characterized by thick, viscid mucus, such as chronic bronchitis, bronchiectasis, and cystic fibrosis, by breaking disulfide bonds in mucus to reduce viscosity and aid clearance. It has been studied for other indications, including prevention of contrast-induced nephropathy and various psychiatric or dermatologic conditions, but evidence is variable and use is context-dependent.

Administration and dosing vary by indication and route. For acetaminophen overdose, intravenous regimens often involve an initial loading dose followed by subsequent infusions, while oral regimens use a multi-dose schedule over a day or two, tailored to metabolite levels and patient risk. For mucolysis, oral NAC is typically prescribed in lower daily doses divided throughout the day, depending on the condition and formulation.

Safety and tolerability are generally favorable. Common adverse effects include nausea, vomiting, and diarrhea; rare hypersensitivity or anaphylactoid reactions can occur with intravenous use. NAC is used under medical supervision, with dosing adjusted to age, kidney function, and clinical purpose.