Acetylcysteine is a phlegmolytic drug and is a mucolytic agent. The sulfhydryl group in acetylcysteine breaks the disulfide bonds in the mucin complex, thereby diluting the sputum and helping it to be expelled. If a patient has a cough with thick, sticky sputum that is difficult to cough up, acetylcysteine can be used to dilute the sputum and thus facilitate the antibiotic’s anti-infective effect. However, if the patient has only a dry cough, at which point the use of acetylcysteine is ineffective, and simply coughs without sputum, it is advisable to use compound methocarbamol, dextromethorphan hydrochloride, etc.