moleculefinder

Acetylcysteine

C5H9NO3S163.2 g/mol Calculated

Also called N-acetyl-L-cysteine, NAC and mercapturic acid.

A modified form of the amino acid cysteine, sold as a mucus thinner and used in hospitals as the antidote for paracetamol overdose.

Sources and notes
  • The introductionfrom sourceMoleculeFinder curated
  • Other namesfrom sourceWikidataIts English label and aliases on Wikidata.
  • Formula and weightcomputedPubChem
  • 2D drawingcomputedPubChem structure, drawn by RDKit
  • 3D modelfrom sourcePubChem 3D conformerLoaded after the page has painted, and on a phone only when you ask for it; the 2D drawing shows until it arrives.

Where you encounter it

Sold over the counter, without a prescription. Acetylcysteine on the product labels we hold.

Medicines

AcetadoteAdded by the makerActive ingredient

Every product and list we hold

Sources and notes
  • The product labels and their strengthsfrom sourceDailyMed (FDA label)Each label lists the molecule as an ingredient, and an active ingredient at the strength shown.
  • How it gets therefrom sourceMoleculeFinder curatedEach mark is set by hand on our lists, never inferred; a label's ingredient is added by the maker. A row with no mark data says Not marked.
  • The line abovefrom sourceMoleculeFinder curatedFrom the group the molecule belongs to.

Explore its structure

Choose a part to light it up.

A carbon carrying both a C=O and an O-H, written COOH. In water it gives up that hydrogen, which is what makes the molecule an acid.

From: standard chemistry.

Sources and notes
  • The drawingcomputedPubChem structure, drawn by RDKitThe page's one shipped drawing, with the chosen part lit in amber under it.
  • The partscomputedFound by ruleEach part is found by a chemical pattern, never picked by hand atom by atom; its words say where they come from.

Properties and sources

Calculated by PubChem

Molecular formula
C5H9NO3S
Molecular weight
163.2 g/mol
XLogP3octanol/water, log units
0.4
Polar surface areatopological
67.4 Ų
H-bond donors
3
H-bond acceptors
4
Rotatable bonds
3
Complexity
148

Measured LD50, HSDB via PubChem

3,000 mg/kg pure acetylcysteine, rat, oral

An LD50 is an animal study measurement, not a dose for a person.

Reported Hazard label (GHS), ECHA via PubChem

Warning Irritant pictogram (GHS07); hazard statements H319

Reported Licence

The US Food and Drug Administration licenses Acetylcysteine for human use (NDA 021539, authorized January 23, 2004), as Acetadote. Drugs@FDA

Groups it belongs to

Category
OTC medicine
Family
Airway medicines
Use
Cough and cold
Chemical groups
Carboxylic Acids, Amides, Thiols
Elements
Nitrogen, Sulfur
Hazard classes
Irritant, GHS Warning
SMILESCC(=O)N[C@@H](CS)C(=O)O

PubChem CID 12035 · Wikidata Q375613 · InChIKey PWKSKIMOESPYIA-BYPYZUCNSA-N · Data refreshed

How MoleculeFinder sources and labels its data

Questions
What is Acetylcysteine?
A modified form of the amino acid cysteine, sold as a mucus thinner and used in hospitals as the antidote for paracetamol overdose.
How toxic is Acetylcysteine?
The reported LD50 of Acetylcysteine is 3,000 mg/kg (rat, oral). An LD50 is an animal study measurement, not a dose for a person. Its GHS hazard label carries the signal word Warning and the hazard pictogram Irritant. from sourcefrom source
What kind of molecule is Acetylcysteine?
Acetylcysteine has the formula C5H9NO3S and a molecular weight of 163.2 g/mol. MoleculeFinder files it under airway medicines, in the OTC medicine group. from sourcefrom sourcefrom sourcefrom source
What else is Acetylcysteine called?
Acetylcysteine is also called N-acetyl-L-cysteine, NAC and mercapturic acid. from source
Who licenses Acetylcysteine as a medicine?
The US Food and Drug Administration licenses Acetylcysteine for human use (NDA 021539, authorized January 23, 2004), as Acetadote. from source
Sources and notes
  • Calculated valuescomputedPubChemComputed from the structure, so no laboratory conditions apply; complexity is PubChem's own structural score.
  • LD50from sourceHSDB via PubChemOther values the sources report: dog, oral, 1,000 mg/kg; mouse, oral, 3,000 mg/kg; rat, oral, 6,000 mg/kg; dog, another route, 700 mg/kg. The page shows the one LD50 the site uses everywhere.
  • Hazard labelfrom sourceECHA via PubChemThe label combines these classifications.
  • ECHAfrom sourceAttributionSource: European Chemicals Agency, echa.europa.eu.
  • Licencefrom sourceDrugs@FDARead 2026-10-21.
  • Data refreshedfrom sourceMoleculeFinder2026-11-09

Keep exploring

Both carry a carboxylic acid and a thiol group.CysteineC3H7NO2S
Sources and notes
  • Similar in shapecomputedRDKit Morgan/TanimotoNeighbours by structural fingerprint; the sentence names the chemical groups the two share.
  • The drawingscomputedPubChem structures, drawn by RDKit