The Reality: Viagra is a brand name for sildenafil, a prescription drug period— the time between ejaculating and being able to have sex again. fatigue, or simply not being in the mood for sex, the first thing to do would be to. When you first take Viagra, you may experience no results at all. You may find you need to take Viagra a few times before the drug will work. Doctors advise taking the pill an hour before you want to have sex, but, it may not take that long to.