The body takes longer to absorb it after a high-fat meal or alcohol. You are encouraged to report adverse events related to Viatris products by calling U. Avanafil Stendra. They’re often the first line of treatment for trouble getting or keeping an erection, called erectile dysfunction ED. This medicine also works best when you take it an hour before sex on an empty stomach. It works for up to 36 hours. If it is not treated right away, priapism can permanently damage your penis sudden vision loss in one or both eyes.Generic versions of sildenafil, vardenafil and tadalafil are available. When oral medications might not be safe Check with your health care team before you take any . Learn about uses, how it works, and more for Viagra (sildenafil). It’s a prescription drug that treats erectile dysfunction (ED) in adult males. Sildenafil oral tablet is available as a brand-name drug and as a generic drug. Brand names: Viagra, Revatio. Sildenafil comes in three forms: an oral tablet, an .