This boosts blood flow and helps you get an erection from sexual activity. Its effects might last longer if you have mild to moderate ED. Rarely reported side effects include: an erection that will not go away priapism. Vardenafil usually works for 4 to 5 hours. Some people may also have ringing in their ears tinnitus or dizziness.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 Missing: hotline. Drug Images What is Viagra? If you have erectile dysfunction (ED), your doctor may recommend that you take Viagra. It’s a prescription drug that’s used in adult Missing: hotline. For further information, call , visit , or write: Viatris Inc., P.O. Box , Mission, KS See risks & benefits. Learn more about what VIAGRA® Missing: hotline.