This increased blood flow can cause an erection. These small differences affect the way each medication works, such as how quickly it takes effect and wears off, and the possible side effects. Ask your pharmacist for a list of the ingredients. These medicines prevent an enzyme called phosphodiesterase type-5 from working too quickly. Other uses for this medicine This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.Generic Viagra (sildenafil) is an alternative to the branded Viagra drug that can be used for treating erectile dysfunction (ED). It’s now sold by many manufacturers, including online. In fact, a recent review of studies found that some counterfeit drugs contained a very high, dangerous level of sildenafil that far exceeded a typical prescription dosage. In , the.  · Viagra; Descriptions. Sildenafil is used to treat men who have erectile dysfunction (also called sexual impotence). Sildenafil belongs to a group of medicines called phosphodiesterase 5 (PDE5) inhibitors. These medicines prevent an enzyme called phosphodiesterase type-5 from working too quickly. The penis is one of the areas where .