Theophylline is mainly applied to the treatment of bronchial asthma, which can significantly improve the wheezing symptoms of asthma patients, divided into oral and intravenous administration, mainly used for severe and critically ill asthma patients. The main adverse effects include nausea, vomiting, cardiac arrhythmia, decreased blood pressure, excessive urination, and can excite the respiratory center, which can cause convulsions and even death in severe cases. Theophylline can also cause serious and even life-threatening reactions if administered too quickly intravenously. Due to the safe concentration of theophylline, the therapeutic window is narrow, so monitor the blood concentration when using theophylline, and use with caution in patients with fever, pregnancy, pediatrics, hepatic and renal insufficiency, and hyperthyroidism.