While each PDE5 inhibitor differs slightly, they’re very similar in treating erectile dysfunction. Its effects often last for 4 to 5 hours. How we source info. You’ll also need to fill out a medical questionnaire with answers about your medical history, current medications, and lifestyle habits. Kidney disease that needs to be treated with dialysis.Generic Sildenafil is like Viagra, without the branding. It works in the same way, and gives very similar results. Talk to us about ED treatment. We’ll recommend the best medication for you, and you can choose which one from there. Order Sildenafil online and get your medication by subscription. The four main medicines taken by mouth for erectile dysfunction are: Avanafil (Stendra). 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. Buy Viagra Online Sildenafil Citrate Eight top reasons you should buy mg tablets of Viagra from : Save money. Our mg Viagra prices are some of the lowest on the Internet. Get a free pill splitter and cut your mg pills into smaller doses to save you money.