<p>Erdosteine is a prodrug that is metabolised into&nbsp;N-thiodiglycolyl-homocysteine whereby free thiol groups are formed leading to the opening of the disulphide bonds of the bronchial mucoproteins, thus reducing the viscosity of mucus and purulent sputum. It also antagonises the local formation of free radicals and inhibits elastase enzyme activity and bacterial adhesion to epithelial cells.</p>