Acetylcysteine, which is not well known to many people, has a significant expectorant effect on patients with chronic obstructive pulmonary disease, or respiratory infections and bronchitis. Adults take 0.6g orally three times a day, i.e. one tablet at a time. Acetylcysteine effectively dissolves purulent sputum and is very effective in expectorating phlegm. It is worth noting that acetylcysteine is a substance with the odor of hydrogen sulfide, which can cause severe persistent cough, spasm in the bronchial tubes, and adverse reactions such as dizziness, nausea and vomiting to varying degrees in some patients, and the above symptoms can be relieved after stopping the drug.