·       Sildenafil (viprogra) is used to treat erectile dysfunction in men. Sildenafil (Viprogra) is used to improve the ability to exercise in people with pulmonary arterial hypertension . Sildenafil is in a class of medications called phosphodiesterase inhibitors. Sildenafil treats ED by increasing blood flow to the during sexual stimulation. This increase blood flow can cause an erection. Sildenafil treats PAH by relaxing the blood vessels in the lungs to allow blood to flow easily.