Mucus and bronchial secretions

Mucus and bronchial secretions constitute a complex viscoelastic gel that lines the respiratory tract, serving as a primary innate defense mechanism [Fahy JV, Dickey BF. N Engl J Med. 2010]. Composed primarily of water, ions, and high-molecular-weight glycoproteins called mucins (notably MUC5AC and MUC5B), this substance traps inhaled pathogens and particulates for removal via mucociliary clearance [Thornton DJ, et al. Annu Rev Physiol. 2008]. In various respiratory diseases such as cystic fibrosis, chronic obstructive pulmonary disease (COPD), and asthma, mucus production becomes excessive or its rheological properties are altered, leading to airway obstruction and recurrent infections [Boucher RC. Paediatr Respir Rev. 2007]. Pharmacological intervention targets these secretions through various mucoactive agents, including mucolytics that break down the chemical structure of mucus, expectorants that increase secretion volume to facilitate clearance, and osmotic agents that hydrate the airway surface [Balsamo R, et al. Eur Respir Rev. 2010]. For instance, N-acetylcysteine reduces the viscosity of mucus by breaking disulfide bonds between mucin monomers, while dornase alfa targets the DNA accumulated from degraded neutrophils in cystic fibrosis sputum [StatPearls. Mucolytics. 2023]. Effective management of bronchial secretions is critical for maintaining airway patency and reducing the inflammatory burden in chronic lung conditions [Rogers DF. Drug Discov Today. 2007].

Other names

Airway mucusRespiratory secretionsSputumPhlegmBronchial mucus

Mucoactive agents act via several mechanisms: mucolytics (e.g., N-acetylcysteine) cleave disulfide bonds in mucin polymers to reduce viscosity; dornase alfa enzymatically digests extracellular DNA; expectorants (e.g., guaifenesin) increase the volume of secretions; and osmotic agents (e.g., hypertonic saline) hydrate the airway surface liquid to facilitate clearance.