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. This product is available in the following dosage forms: Tablet Suspension There is a problem with information submitted for this request. Rarely reported side effects include: an erection that will not go away priapism. Without physical action to the penis, such as that occurring during sexual intercourse, sildenafil will not work to cause an erection. The penis is one of the areas where this enzyme works. If you are a Mayo Clinic patient, this could include protected health information. Click here for an email preview.The Savings Offer and Program expire on 12/31/ For further information, call , visit test1.ru, or write: Viatris Inc., P.O. Box , Mission, KS See risks & benefits. Learn more about what VIAGRA® (sildenafil citrate), a prescription treatment for ED. What is Sildenafil (Viagra)? Drug Facts Common Brands Viagra Drug Class PDE-5 inhibitor Controlled Substance Classification Not a controlled medication Generic .  · Viagra comes as an oral tablet that contains the active drug sildenafil. Sildenafil is also available in generic form. Viagra is classified as a phosphodiesterase type 5 (PDE5) inhibitor.