N-acetylcysteine (NAC), the acetylated variant of the amino acid L-cysteine, is an excellent source of sulfhydryl (SH) groups and is converted in the body into metabolites capable of stimulating glutathione (GSH) synthesis, promoting detoxification and acting directly as a free radical scavenger.
The administration of NAC has been used in the past as an expectorant in a variety of respiratory diseases, but it also appears to have beneficial effects in conditions characterized by decreased GSH or oxidative stress, such as HIV infection, cancer, heart disease and cigarette smoking.
Oral administration of 15-20 doses of NAK is currently the mainstay of treatment for paracetamol-induced hepatotoxicity.
N-acetylcysteine also appears to have some clinical utility as a chelating agent in the treatment of acute heavy metal poisoning, both as a means of protecting the liver and kidney from damage and as an intervention to improve excretion of the metals.