Be sure to let your doctor and pharmacist know that you are taking these medications before you start taking sildenafil. The following information includes only the average doses of this medicine. There is a problem with information submitted for this request. If you are a Mayo Clinic patient, this could include protected health information. Sildenafil may cause side effects. Children—Use is not recommended. It might work longer if you have mild to moderate erectile dysfunction.Viagra (sildenafil) is a brand-name prescription drug that’s used to treat erectile dysfunction (ED). Learn about side effects, warnings, dosage, and more. Sildenafil (Viagra) is used to treat erectile dysfunction (impotence; inability to get or keep an erection) in men. Sildenafil (Liqrev, Revatio) is used to improve the ability to exercise in . Learn about uses, how it works, and more for Viagra (sildenafil). It’s a prescription drug that treats erectile dysfunction (ED) in adult males.