DESC: Sildenafil citrate, sold under the name Viagra is the first of a new group of medication whichallows adequate sexual stimulation, relaxes the blood vessels of the penis and helps erection. Sildenafil tablet should be taken once a day. The time necessary for Sildenafil to exercise its action is about half an hour. The effect is maintained for about four hours.The effect is only obtained with a satisfactory sexual stimulation.