We rely on peer-reviewed studies, academic research institutions, and medical associations. This patent was published in and expired in Keep out of the reach of children. Mondaini, N. We strive to use primary sources and refrain from using tertiary references.Since , Viagra (sildenafil) has been used for treating erectile dysfunction (ED). It’s available by prescription for males ages 18 years and older. Side effects are . Viagra is used to treat erectile dysfunction (ED). It decreases ED symptoms by helping you get and keep an erection. Erections happen when a protein called cyclic . Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 inhibitors. They enhance the effects of a chemical the body makes that relaxes .