Acetylcysteine

Acetylcysteine may protect against acetaminophen overdose-induced hepatotoxicity by maintaining or restoring hepatic concentrations of glutathione. It does this by producing the glutathione precursor cysteine. Glutathione is required to inactivate an intermediate metabolite (N-acetyl-p-benzoquinoneimine) of acetaminophen that is thought to be hepatotoxic. In acetaminophen overdose, excessive quantities of this metabolite are formed because the primary metabolic (glucuronide and sulfate conjugation) pathways become saturated. Acetylcysteine may act by reducing the metabolite to the parent compound and/or by providing sulfhydryl for conjugation of the metabolite. Experimental evidence also suggests that a sulfhydryl-containing compound such as acetylcysteine may also directly inactivate the metabolite. When inhaled, cetylcysteine exerts its mucolytic action through its free sulfhydryl group, which opens the disulfide bonds and lowers mucus viscosity. This action increases with increasing pH and is most significant at pH 7 to 9. The mucolytic action of acetylcysteine is not affected by the presence of DNA. Acetylcysteine is also an antioxidant and reduces oxidative stress.