The duration of acetylcysteine effervescent tablets is decided according to the specific disease, the length of treatment varies from disease to disease, you need to follow the doctor’s professional guidance to use. Acetylcysteine belongs to the mucous phlegm dissolving drug among expectorants, and is suitable for breathing and sputum difficulty caused by phlegm viscosity, such as chronic obstructive pulmonary disease, chronic bronchitis, emphysema and so on. Acetylcysteine has a special odor and is irritating to the respiratory tract, and should be used with caution in the elderly with asthma. The viscosity of sputum originates from two main sources: mucin secreted by the glands or cup cells of the trachea and bronchi, and substances released by a large number of broken inflammatory cells after respiratory tract infections. Common adverse reactions to acetylcysteine include rash, cardiac arrhythmia, nausea and vomiting, etc. It is contraindicated in people who are allergic to the drug and in patients with phenylketonuria. The use of drugs must follow the doctor’s instructions, not blindly use their own medication, so as not to cause adverse consequences.