Insurance can help you save even more on consultations and medications. How effective is Viagra? This allows the smooth muscles in the penis to relax and fill with blood. Cialis Tadalafil is a tablet that does the same job but works for up to 36 hours, Stendra Avanafil has a faster average response time of 15 minutes, and Levitra Vardenafil is a more potent drug and is thought to be less likely to cause side effects. Viagra is the most recognizable and well-known ED tablet. It’s best to check your chosen provider’s site for more information.Learn More IF YOU CHOOSE BRAND-NAME VIAGRA, MAKE SURE YOU GET THE BRAND NAME Your prescription may have been filled with a generic version instead of . Cart. Transfer your prescription for Sildenafil (Generic for Viagra, Oral Tablet) on Amazon Pharmacy. FREE SHIPPING for Prime members. To purchase generic Viagra (sildenafil) and brand-name Viagra through Optum Store, you must fill out a questionnaire, upload a photo ID, and provide a recent blood pressure .