Sildenafil works for PAH by relaxing the blood vessels in the lungs, which decreases pulmonary pressure and helps the heart pump blood more easily. Clinical trials and studies have shown that Sildenafil, in both branded and generic forms, can improve exercise capacity and reduce symptoms in PAH patients. The use of Sildenafil for PAH has been approved by regulatory agencies in many countries under different brand names, such as Revatio.