Revatio 20mg is a medication that contains sildenafil citrate. It is primarily used to treat pulmonary arterial hypertension (PAH), a condition where there is high blood pressure in the arteries that supply the lungs. Revatio, works by relaxing the blood vessels in the lungs, allowing blood to flow more easily. This helps to reduce the workload on the heart and improve symptoms of PAH, such as shortness of breath.