MOA Erdosteine, is an orally administered mucolytic agent. It is classified as a thiol derivative and produced for the management of symptoms caused by chronic obstructive bronchitis. Erdosteine contains sulfhydryl groups which are released after hepatic first-pass metabolism in the liver. Its active metabolites (3 in number) exert both mucolytic activity and scavenging activity against free radicals. Erdosteine acts to regulate the production of mucus in the airway and regulates its viscosity while enhancing mucociliary transport. This leads to an increase in expectoration. Erdosteine shows inhibition against the effects of free radicals from cigarette smoke. Clinical studies in patients with chronic obstructive lung disease (COPD) have shown that this drug is generally safe and well tolerated. Erdosteine 300mg twice daily reduced cough (both frequency and severity) and sputum viscosity more quickly and more effectively than placebo and reduced the adhesivity of sputum more effectively than ambroxol 30mg twice daily. Co-administration of erdosteine and amoxicillin in patients with acute infective exacerbation of chronic bronchitis resulted in higher concentrations of the antibiotic in the sputum, leading to earlier and more pronounced amelioration of clinical symptoms compared with placebo. Erdosteine is associated with a low incidence of adverse events, most of which are gastrointestinal and generally mild.