Phlegm is a complex mix of inflammatory products, secreted peptides and micro-organisms in the airway, and is referred to as sputum when it is expectorated.2
The respiratory mucus is a complex biological material, which deforms in pathological conditions and returns to normal when the stress is removed (viscoelasticity).3
Mucus with low viscosity and elasticity is transported by ciliary action with more ease, whereas pathological mucus is less easily cleared and has a higher elasticity and viscosity.4
Mucoactive drugs are meant...