Theophylline tablets are theophylline extended-release tablets with side effects related to the serum concentration of the drug, including nausea, vomiting, insomnia, etc. Contraindications include those who are allergic to the product. Theophylline extended-release tablets can directly relax the smooth muscle of the respiratory tract, suitable for the relief of wheezing symptoms caused by wheezing bronchitis, bronchial asthma, obstructive emphysema and other diseases, can also be used for the treatment of asthma caused by cardiogenic pulmonary edema, but is not applicable to patients with acute bronchospasm attacks or persistent asthma. The side effects of the drug are related to the serum concentration of the drug, when theophylline serum concentration is 15-20μg/ml, nausea, vomiting, insomnia, agitation and so on are mostly seen in the early stage, when the serum concentration is >20μg/ml, arrhythmia and tachycardia can occur, when the serum concentration is >40μg/ml, convulsions, loss of water, fever and other symptoms, and in severe cases, death can be caused by respiratory and cardiac arrest. Contraindications for use include hypersensitivity to the product, those with active peptic ulcers, and patients with uncontrolled convulsive disorders. Specific medication should be administered under the guidance of a specialist.