Filitra 40 mg contains sildenafil citrate, a phosphodiesterase type 5 (PDE5) inhibitor. Doctors prescribe it to patients with pulmonary hypertension because it helps relax and widen the blood vessels in the lungs. This relaxation reduces the pulmonary arterial pressure, making it easier for the heart to pump blood through the lungs. By lowering resistance in the lung arteries, sildenafil improves oxygen flow and reduces symptoms like shortness of breath, fatigue, and chest pain. This can enhance exercise capacity and quality of life in patients with pulmonary arterial hypertension. Overall, Filitra 40 mg helps manage the condition by targeting the underlying vascular problem.