Theophylline is an off-label treatment for central sleep apnea that works by stimulating the brain’s respiratory centers and increasing diaphragmatic activity. It may be helpful in patients with CSA related to heart failure or neuromuscular conditions, especially when standard therapies like CPAP or ASV are not tolerated. However, its use is limited by a narrow therapeutic window and potential side effects such as insomnia, tremors, and cardiac arrhythmias. Because of these risks, theophylline is generally reserved as an adjunct therapy rather than first-line treatment. It requires careful monitoring and is less commonly used today due to the availability of safer, more effective alternatives.