Sildenafil (Viagra) is a tablet that's taken by mouth for erectile dysfunction (ED) in adults. It works as a phosphodiesterase-5 (PDE5) inhibitor to help people get an erection or keep an erection that lasts for sex. Find drug information for Viagra on CVS.com, including related drug classes, side effects, dosage, and answers to frequently asked questions. In addition to being available as the brand-name drug Viagra, it’s available as a generic drug. Here we look at how Viagra and sildenafil are alike and different. There is no generic version, so it’s a little more expensive. A typical dose of avanafil is about 50–100 mg, and it takes about 45 minutes to start working. Avanafil also carries similar risks of. Find patient medical information for Sildenafil (Viagra, Revatio) on WebMD including its uses, side effects and safety, interactions, pictures, warnings, and user ratings If you take sildenafil for pulmonary arterial hypertension, do not take Viagra®, Vibrique™ or other PDE5 inhibitors, including tadalafil (Cialis®) or vardenafil (Levitra®). Viagra relaxes muscles found in the walls of blood vessels and increases blood flow to particular areas of the body. Viagra is used to treat erectile dysfunction (impotence) in men.