An expectorant increases bronchial secretions and mucolytics help loosen thick bronchial secretions. Expectorants reduce the thickness or viscosity of bronchial secretions thus increasing mucus flow that can be removed more easily through coughing.Mucolytics break down the chemical structure of mucus molecules.ucokinetics are a class of drugs which aid in the clearance of mucus from the airways, lungs, bronchi, and trachea. Such drugs can be further categorized by their mechanism of action: 1  mucolytic agents.