N-acetylcysteine is the acetylated variant of the amino acid L-cysteine and is widely used as the specific antidote for acetaminophen overdose. Other applications for N-acetylcysteine supplementation supported by scientific evidence include prevention of chronic obstructive pulmonary disease exacerbation, prevention of contrast-induced kidney damage during imaging procedures, attenuation of illness from the influenza virus when started before infection, treatment of pulmonary fibrosis, and treatment of infertility in patients with clomiphene-resistant polycystic ovary syndrome. Preliminary studies suggest that N-acetylcysteine may also have a role as a cancer chemopreventive, an adjunct in the eradication of Helicobacter pylori, and prophylaxis of gentamicin-induced hearing loss in patients on renal dialysis.