Viagra is also informally known as “vitamin V”, “the blue pill”, or “blue diamond”, as well as various other nicknames. Generic versions of sildenafil, vardenafil and tadalafil are available. Let’s learn more about Viagra, how it’s dosed, and what to watch out for when a person has been prescribed this medication. These small differences affect the way each medication works, such as how quickly it takes effect and wears off, and the possible side effects. Side effects Side effects of oral ED medicines are often mild. Vardenafil usually works for 4 to 5 hours.The four main medicines taken by mouth for erectile dysfunction are: Avanafil (Stendra). Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called . Cost Overdose Ask your doctor Q&A Drug Images What is Viagra? If you have erectile dysfunction (ED), your doctor may recommend that you take Viagra. It’s a . CHOOSE BRAND-NAME VIAGRA. The original little blue pill prescribed by doctors for over 20 years. Clinically proven to treat men with erectile dysfunction (ED) Ongoing .