Write down questions to ask your doctor. Sorry something went wrong with your subscription Please, try again in a couple of minutes Retry Clinical trials Explore Mayo Clinic studies testing new treatments, interventions and tests as a means to prevent, detect, treat or manage this condition. This is a type of high blood pressure that occurs between the heart and the lungs. Sildenafil may cause side effects. There is a problem with information submitted for this request. Severe liver disease.Sildenafil is a prescription drug. It comes in the form of a tablet and suspension (liquid). Both are taken by mouth. It also comes in an intravenous (IV) form, . Sildenafil is in a class of medications called phosphodiesterase (PDE) inhibitors. Sildenafil treats erectile dysfunction by increasing blood flow to the penis during sexual stimulation. . For many people, a physical exam and answering questions (medical history) are all that’s needed for a doctor to diagnose erectile dysfunction and recommend a treatment. If you have chronic health conditions or your doctor suspects that an underlying condition might be involved, you might need further See more.