Recent heart or blood vessel problems. Sildenafil is a drug that helps improve blood flow to the penis, allowing you to achieve a firm, longer-lasting erection more easily. Vardenafil usually works for 4 to 5 hours. You can take this medicine with or without food 30 minutes before sex, depending on the dose. Medicines that you take by mouth are called oral medicines. They’re often the first line of treatment for trouble getting or keeping an erection, called erectile dysfunction ED.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 prescription . Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 inhibitors. They enhance the effects of a chemical the body makes that relaxes muscles . Can You Buy Viagra Over the Counter? A straightforward answer: Yes! Since , the ED medication Viagra has been available over the counter at many pharmacies, under the .