Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Sorry something went wrong with your subscription Please, try again in a couple of minutes Retry. This will increase the supply of blood to the lungs and reduce the workload of the heart. You’ll soon start receiving the latest Mayo Clinic health information you requested in your inbox. Erectile dysfunction is a condition where the penis does not harden and expand when a man is sexually excited, or when he cannot keep an erection. Use the oral syringe provided with your medication to measure and take your dose.Sildenafil is in a class of medications called phosphodiesterase (PDE) inhibitors. Sildenafil treats erectile dysfunction by increasing blood flow to the penis during sexual . · Sildenafil is used to treat men who have erectile dysfunction (also called sexual impotence). Sildenafil belongs to a group of medicines called phosphodiesterase . Sildenafil oral tablet is available as a brand-name drug and as a generic drug. Brand names: Viagra, Revatio. Sildenafil comes in three forms: an oral tablet, an .