Side effects Side effects of oral ED medicines are often mild. Medicines that you take by mouth are called oral medicines. Many people have no side effects or only mild ones. The four main medicines taken by mouth for erectile dysfunction are: Avanafil Stendra. How oral medicines differ Each oral medicine for ED has a slightly different chemical makeup.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 males* with . Viagra works by increasing blood flow to your penis, which helps you have and keep an erection. But this drug only works if you’re sexually aroused. Viagra comes as tablets . Taking Viagra or similar medications daily can benefit your urinary and sexual health. Some people may experience mild side effects that typically go away with time. A conversation .