You may take this medicine with or without food. These are commonly prescribed for an enlarged prostate or male pattern baldness. They include dutasteride Avodart, Jalyn and finasteride Propecia, Proscar. If it is not treated right away, priapism can permanently damage your penis sudden vision loss in one or both eyes. Rarely reported side effects include: an erection that will not go away priapism. It works for up to 36 hours.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 . Take sildenafil as needed before sexual activity. The best time to take sildenafil is about 1 hour before sexual activity, but you can take the medication any time from 4 hours to 30 . CHOOSE BRAND-NAME VIAGRA. The original little blue pill prescribed by doctors for over 20 years. Clinically proven to treat men with erectile dysfunction (ED) Ongoing .