N-acetylcysteine (NAC) !

A cysteine derivative that refills liver glutathione; it is the antidote for acetaminophen poisoning.

Updated 2026-11-01

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Key facts

It is deacetylated to cysteine, the amino acid that limits glutathione synthesis.
Acetaminophen antidote: it refills GSH, supplies sulfate for sulfation and may neutralise some NAPQI directly.
It protects almost completely when given in the first hours; even late, it improves the course of liver failure.
It is also a mucolytic: it breaks disulfide bonds in mucus.

The decision uses the Rumack-Matthew nomogram (acetaminophen level by hours) or any sign of liver injury.
The intravenous route can cause anaphylactoid reactions (flushing, bronchospasm), usually managed by slowing the infusion.
Doses and schedules are set by the poison-centre protocol.

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How does N-acetylcysteine protect the liver in acetaminophen poisoning?

It supplies cysteine to rebuild the glutathione that neutralises NAPQI.

When is N-acetylcysteine most effective?

In the first hours after ingestion, before glutathione is depleted.

What typical adverse effect does the intravenous route have?

Anaphylactoid reactions such as flushing, hives or bronchospasm.

Molecules are shown in their neutral form, as the databases deposit them; in the cell the acids and phosphates are ionised.

Educational information, not medical advice. For any symptom, see a health professional.

Sources: N-Acetyl-L-Cysteine (CID 12035) (PubChem, NCBI, 2026); Acetaminophen overdose: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); Paracetamol ADME (Reactome, 2026).

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Representative model, for educational purposes only.