Xofyl 400 mg is a bronchodilator containing Doxophylline, a novel xanthine derivative. It differs from Theophylline by incorporating a dioxolane group at the N-7 position, enhancing its selectivity and safety profile. Doxophylline primarily inhibits phosphodiesterase 4 (PDE4), leading to the relaxation of bronchial smooth muscles and improved airflow. Additionally, it has reduced affinity for adenosine A1 and A2 receptors, contributing to fewer side effects.