Clinical application of expectorants Under normal conditions, a fluid consisting of many components is present in the respiratory tract, which is mainly secreted by mucus-secreting glands and cupula cells of the bronchial mucosa epithelium. Among them, there are clear proteins, glycoproteins, anti-microbial proteins and protease inhibitors. The presence of this fluid acts as a lubricant for the respiratory tract and, in combination with the mechanical activity of epithelial cilia, acts as a conveyor belt, transporting dirt out of the airways at a rate of 10 to 20 microns per minute or expelling it with coughing. Sputum is produced by changes in respiratory fluid when inflammatory lesions occur in the respiratory tract. Sputum contains mucus, foreign matter, pathogenic microorganisms, various inflammatory cells and necrotic shed mucosal epithelial cells, and other components. It can irritate the respiratory tract mucosa causing coughing and can aggravate infection. Expectorants are a class of drugs that make sputum thinner, less viscous, and easier to cough up, or accelerate the movement of respiratory mucous membrane cilia and improve sputum transport, so they are also called mucus-activating drugs. Through the effect of expectorant drugs, it can promote the discharge of sputum accumulated in the lumen of respiratory tract, reduce the stimulation of respiratory tract mucosa, indirectly play the role of cough suppressant and asthma calming, and also help control secondary infection. Therefore, the rational application of expectorants is one of the important measures in the treatment of respiratory system diseases and is an indispensable treatment method in every treatment session. Expectorants can be divided into two categories according to their different mechanisms of action: mucus secretion promoting drugs and mucus phlegm dissolving drugs: 1. Mucus secretion promoting drugs: (1) Nausea expectorants, which are generally administered orally. For example, ammonium chloride, potassium iodide, Chinese herbal medicine, Yuan Zhi, etc., which are commonly used clinically, can stimulate gastric mucous membrane receptors through oral administration and cause slight nausea through gastric-pulmonary vagal reflex, and reflexively promote increased secretion of respiratory glands to dilute sputum and make it easy to be expelled. Indications – This class of expectorants is weak and better for acute respiratory tract infections. (2) Stimulating expectorants, such as eucalyptus oil, tincture of benzoin, etc. Add these volatile substances to boiling water, and their vapors can stimulate the respiratory mucous membrane, make the mucous membrane lightly congested, increase glandular secretion, make the sputum thin and easy to emit. Indications – This class of drugs is commonly used as respiratory physical therapy drugs, such as nebulization and other treatments. 2.Mucolytic drugs: (1) Mucolytic agents: such as N-acetyl cysteine (sputum easy net or easy cough net), can break down the sticky components of sputum such as mucopolysaccharide and mucin, so that the sputum liquefies and the stickiness decreases and it is easy to emit. Indications-Adapted to those whose sputum is sticky and not easy to be expelled due to various respiratory tract diseases. (2) Mucus regulators: such as bromoxyn (must be cushioned), amiloride (mucosolvan, lambdain) and carboxymethyl cysteine (carboxymethylstilbestrol, trade name: phlegmolytic tablets or barring), trypsin (good for alveolar protein deposition), sodium bicarbonate solution (for nebulization) of 2% to 7.5% mainly acts on mucous membrane producing cells of trachea and bronchus to promote secretion of low mucus secretion, so that the respiratory The rheology of secretion is restored to normal, and the sputum is changed from sticky to thin and easy to be expelled. Indications – It is suitable for those who have sticky sputum caused by various respiratory tract diseases and cannot be easily expelled.