Mucoactive agents are a class of drugs which aid in the clearance of mucus from the upper and lower airways, including the lungs, bronchi, and trachea. Mucoactive drugs include expectorants, mucolytics, mucoregulators, and mucokinetics. These medications are used in the treatment of respiratory diseases that are complicated by the oversecretion of mucus. The drugs can be further categorized by their mechanism of action.
Mechanism of action
- Expectorants – induce coughing 
- Mucolytics – thin the mucus. 
- Mucokinetics – enables easier transportation of cough 
- Mucoregulators – suppress underlying mechanisms of mucus hypersecretion 
In general, clearance ability is hampered by the bonding to surfaces (stickiness), and by the viscosity of mucous secretions in the lungs. In turn, the viscosity is dependent upon the concentration of mucoprotein in the secretions.
Expectorants and mucolytic agents are different types of medication, yet both are intended to promote drainage of mucus from the lungs.
An expectorant (from the Latin expectorare, to expel or banish) works by signaling the body to increase the amount or hydration of secretions, resulting in more yet clearer secretions and as a byproduct lubricating the irritated respiratory tract.
One expectorant, guaifenesin, is commonly available in many cough syrups and also as long release tablets. Often the term "expectorant" is incorrectly extended to any cough medicine, since it is a universal component. Mucolytics can dissolves thick mucus and are usually used to help relieve respiratory difficulties. They do this by breaking down the chemical bonds between molecules in the mucus. This in turn can lower the viscosity by altering the mucin-containing components.
Any of these effects could improve airway clearance during coughing.
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. The mucus becomes thinner and can be removed more easily through coughing.— Adams, Holland, & Bostwick, 2008, p. 591
- Balsamo, R.; Lanata, L.; Egan, C. G. (2010). "Mucoactive drugs". European Respiratory Review : An Official Journal of the European Respiratory Society. 19 (116): 127–33. doi:10.1183/09059180.00003510. PMID 20956181.
- Rogers, D. F. (2007). "Mucoactive agents for airway mucus hypersecretory diseases". Respiratory Care. 52 (9): 1176–93, discussion 1193–7. PMID 17716385.
- "Definition of Expectorant". MedicineNet. 13 May 2016. Retrieved 4 January 2018.
- "NCATS Inxight: Drugs — MECYSTEINE HYDROCHLORIDE". drugs.ncats.io. Retrieved 29 May 2019.
- Adams, Michael; Holland, Leland Norman; Bostwick, Paula Manuel (2016). Pharmacology for Nurses: A Pathophysiologic Approach (5 ed.). Pearson Education. p. 960. ISBN 978-0134255163.
- Rubin, Bruce K (1 July 2007). "Mucolytics, Expectorants, and Mucokinetic Medications". Respiratory Care. 52 (7).
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