RESUMEN
Mucus is a complex polymeric hydrogel that serves as a critical defense in several organs. In the lungs, it provides a formidable barrier against inhaled particles such as microorganisms. In addition, mucus is essential for normal lung physiology, as it promotes immune tolerance and facilitates a normal commensal pulmonary microbiome. Hypersecretion of airway mucus is a characteristic of numerous respiratory diseases, such as Chronic Obstructive Pulmonary Disease (COPD) and Cystic Fibrosis (CF), and creates pulmonary obstruction, limiting the effectiveness of inhaled therapies. Due to those alterations, therapeutic strategies must be optimal to limit airway obstruction and restore pulmonary function. Mucoactive drugs are common therapeutic options and are classified into different groups depending on their modes of action, i.e., expectorants, mucokinetics, mucoregulators and mucolytics. This review focuses on mucoactive drugs and their modes of action. A special focus will be made on two challenging pulmonary pathologies: COPD and CF, and on their clinical studies conducted with mucoactive drugs.