Sildenafil is a drug that helps improve blood flow to the penis, allowing you to achieve a firm, longer-lasting erection more easily. This applies, for example, when you want to take Tadalafil brand name Cialis instead of Viagra. Ordering Viagra online from a reputable site provides a safe, discreet, simple way to buy your ED medication. Rarely reported side effects include: an erection that will not go away priapism. Otherwise, Viagra and Viagra Connect are both taken in the same way: one tablet about an hour before sex — and only one tablet per day.Viagra is usually taken only when needed, 30 minutes to 1 hour before sexual activity. You may take it up to 4 hours before sexual activity. Other drugs may interact with sildenafil, including prescription and over-the-counter medicines, vitamins, and herbal products. . Clinically proven to treat men with erectile dysfunction (ED) Ongoing commitment to product quality and safety monitoring Learn More IF YOU CHOOSE BRAND-NAME VIAGRA, MAKE SURE YOU GET THE BRAND NAME Your prescription may have been filled with a . There are also a few OTC alternatives to Viagra that may be worth exploring as well. Takeaway Generic Viagra, or sildenafil citrate, works the same as Viagra, but at a lower cost.