N-acetyl-L-cysteine is an N-acetyl-L-amino acid that is the N-acetylated derivative of the natural amino acid L-cysteine. It has a role as an antiinfective agent, an antioxidant, an antiviral drug, an antidote to paracetamol poisoning, a vulnerary, a mucolytic, a human metabolite and a radical scavenger. It is a L-cysteine derivative, an acetylcysteine and a N-acetyl-L-amino acid. It is a conjugate acid of a N-acetyl-L-cysteinate.