Pharmacology: N-acetylcysteine exerts an intensive mucolytic-fluidifying action on mucous and mucopurulent secretions, by depolymerizing the mucoproteic complexes and the nucleic acids which confer viscosity to the vitreous and purulent component of the sputum and of the secretions.
Furthermore, N-acetylcysteine exert a direct antioxidant action, being provided with a free thiol (-SH) nucleophilic group which is able to interact directly with the electophilic group of the oxidant radicals. Of particular interest is the recent demonstration that N-acetylcysteine protects α-1-antitrypsin, enzyme inhibiting elastase, from the inactivation due to the action of hypochlorous acid (HOCl), a powerful oxidant agent produced by the myeloperoxidase enzyme of activated phagocytes.
Due to its molecular structure, N-acetylcysteine can easily cross the cellular membranes. Inside the cell, N-acetylcysteine is deacetylized to L-cysteine, an amino acid is indispensable for the glutathione synthesis (GSH).
GSH is a highly reactive tripeptide, found ubiquitously in the various tissue of animals and is essential for the maintenance of functional capacity as well as cellular morphological integrity, as it represents the most important protective, endocellular mechanism against oxidant radical, either of external or internal nature, as well as toward numerous cytotoxic substances. These features make N-acetylcysteine particularly suitable for the treatment of acute and chronic infections of the respiratory system, characterized by thick viscous and mucopurulent secretions.
N-acetylcysteine plays a role of primary importance in the maintenance of adequate GSH levels that contributing to the cellular protection from harmful agents which through progressive GSH depletion, would be able to express their cytotoxic action, as in case of acetaminophen poisoning.
Due to this mechanism of action, N-acetycysteine also indicated as a specific antidote in acetaminophen poisoning, in the course of cyclophosphamide treatment and hemorrhagic cystitis in the letter case it provides SH- groups necessary to inactivate acrolein, a toxic metabolite that is reported to be responsible of uropathy during chemotherapic.
Due to its antioxidant properties as precursor of the endocellular glutathione, acetylcysteine can also protect the respiratory tract opposing the harmful effect of the oxidant agents.