Mechanism of Action of Mucinac 600 (Acetylcysteine)
Mucinac 600 (acetylcysteine) works primarily by cleaving disulfide bonds in mucoproteins through its free sulfhydryl group, which directly reduces the viscosity of respiratory secretions and makes them easier to clear from the airways. 1, 2
Primary Mucolytic Mechanism
The sulfhydryl group in acetylcysteine "opens" disulfide linkages in mucus proteins, thereby lowering viscosity and making thick secretions easier to expectorate from the tracheobronchial tree 1, 2
This mucolytic activity is unaltered by the presence of DNA (which accumulates in purulent secretions from cellular debris) and increases with increasing pH, with significant mucolysis occurring between pH 7 and 9 2
The drug is rapidly absorbed from the GI tract and quickly appears in active form in lung tissue and respiratory secretions, allowing it to exert its effects directly at the site of action 1
Secondary Antioxidant and Anti-inflammatory Mechanisms
Acetylcysteine functions as a free-radical scavenger and serves as a precursor for glutathione synthesis, providing antioxidant protection beyond its mucolytic effects 3, 4
The antioxidant activity stems from fast reactions with hydroxyl radicals, nitrogen dioxide, carbonate radicals, and thiyl radicals, as well as restoration of impaired targets in vital cellular components 4
Acetylcysteine can efficiently reduce disulfide bonds in proteins, altering their structures and disrupting ligand bonding, which contributes to its anti-inflammatory properties 4
Pharmacokinetic Properties
After oral administration of 200-400 mg, peak plasma concentrations of 0.35-4 mg/L are achieved within 1-2 hours 5
The drug undergoes rapid deacetylation in vivo to yield cysteine or oxidation to yield diacetylcystine, with approximately 70% of total body clearance being nonrenal 2, 5
Protein binding is significant at approximately 50% four hours after dosing, and the terminal half-life following oral administration is 6.25 hours 5
Important Clinical Caveat
Some patients may develop increased airways obstruction of unpredictable severity when exposed to inhaled acetylcysteine aerosol, and these reactors cannot be identified beforehand 2
Most patients with bronchospasm respond quickly to bronchodilators given by nebulization, but if bronchospasm progresses, the medication should be discontinued immediately 2
When used as a 10% solution with a bronchodilator by pressure machine, clearance can be achieved in asthmatic subjects without inducing bronchospasm 6