As with sildenafil, a high-fat meal or alcohol keep the body from absorbing it as quickly. If you have an erection that lasts more than 4 hours, get medical help right away. It works for up to 36 hours. This medicine also works best when you take it an hour before sex on an empty stomach. Stop taking VIAGRA and call your healthcare provider right away if you have any sudden vision loss sudden hearing decrease or hearing loss. Side effects Side effects of oral ED medicines are often mild.Viagra is available as the generic drug sildenafil. A generic drug is considered as safe and effective as the original drug. And generics tend to cost less than brand-name drugs. 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 . You don’t need to take Viagra regularly each day. Viagra generic form. Viagra is a brand-name medication. It’s also available in a generic form called sildenafil.