It lasts 4 to 5 hours, or longer if you have mild to moderate ED. This site is intended only for U. They include dutasteride Avodart, Jalyn and finasteride Propecia, Proscar. Rarely reported side effects include: an erection that will not go away priapism. The products discussed in this site may have different product labeling in different countries. Generic versions of sildenafil, vardenafil and tadalafil are available.Drug Images What is Viagra? If you have erectile dysfunction (ED), your doctor may recommend that you take Viagra. It’s a prescription drug that’s used in adult . 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. The four main medicines taken by mouth for erectile dysfunction are: Avanafil (Stendra). Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called .