The biggest side effect of aminophylline is bronchodilation, which tends to lead to a weakened bladder contraction and causes urinary retention in male patients. In male patients, as they age, the prostate gland gradually enlarges, resulting in frequent urination, incomplete urination, increasing residual urine, reduced bladder contraction, and reduced bladder compliance. With the use of aminophylline, the patient’s bronchial tubes can be relaxed and the bronchospasm can be relieved, while the sphincter contraction of the bladder will be relaxed and the contraction of the bladder will be reduced, resulting in increased urinary retention and difficulty in urination. This condition requires oral alpha-blockers to release urinary retention and effectively relieve the difficulty in urination.