Some people may also have ringing in their ears tinnitus or dizziness. Depending on your needs and preferences, you have the option to take it either on an as-needed basis or daily if prescribed by your doctor. Find answers What does Viagra do? They enhance the effects of a chemical the body makes that relaxes muscles in the penis, called nitric oxide. You take one 2.Drug Images What is Viagra? Viagra is a brand-name prescription drug that’s approved to treat erectile dysfunction (ED). With ED, you’re unable to have or maintain an erection. Viagra is. Price without insurance: starts at $80 per dose. Doses: 25, 50, and milligrams (mg) Supply: 30 or 90 days. To get a prescription for Viagra through the Optum Store, you’ll need to complete a. Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 inhibitors. They enhance the effects of a chemical the body makes that relaxes muscles in the penis, called nitric oxide. This boosts blood flow and helps you get an erection from sexual activity. How oral medicines differ.