It works for up to 36 hours. Finding an online ED provider can feel overwhelming. Other conditions that may disqualify you from an ED prescription include a history of stroke, kidney or liver disease, cancer, diabetes, or a bleeding disorder. Generic versions of sildenafil, vardenafil and tadalafil are available. They have the same benefits and risks as their brand-name counterparts. While each PDE5 inhibitor differs slightly, they’re very similar in treating erectile dysfunction.Ways to save on Viagra. Below, we discuss four ways you can save on Viagra, whether you have insurance or not. 1. Check your insurance coverage. Insurance companies are . Sildenafil (Viagra). This medicine works best when you take it on an empty stomach an hour before sex. The body takes longer to absorb it after a high-fat meal or alcohol. Its . Best for Generic Pills: Sesame; Best for Daily Cialis: Lemonaid; Best for Viagra: Roman;.