Treating sexual function problems in men, such as impotence or erectile dysfunction. Sildenafil relaxes muscles and increases blood flow to particular areas of the body. Sildenafil under the name Viagra is used to treat erectile dysfunction (impotence) in men. Another brand of sildenafil is Revatio, which is used to treat pulmonary arterial hypertension and improve exercise capacity in men and women. It works by dilating blood vessels in the penis, allowing the inflow of blood needed for an erection.