Sildenafil Viagra. Sildenafil treats erectile dysfunction by increasing blood flow to the penis during sexual stimulation. As with sildenafil, a high-fat meal or alcohol keep the body from absorbing it as quickly. Sildenafil Viagra is used to treat erectile dysfunction impotence; inability to get or keep an erection in men. Kidney disease that needs to be treated with dialysis.dizziness. If you have these symptoms, stop taking VIAGRA and contact a doctor right away Before you take VIAGRA, tell your healthcare provider if you: • have or have had . If you have certain health conditions or are taking certain medications, your doctor may tell you to take sildenafil less often. You can take sildenafil with or without food. However, if . Overdose Ask your doctor Q&A Drug Images What is Viagra? If you have erectile dysfunction (ED), your doctor may recommend that you take Viagra. It’s a prescription .