International name: Sildenafil Using sildenafil take one tablet before planned sexual intercourse. The mechanism of action of Sildenafil: the drug increases the amount of blood flowing to the penis. This helps a man to call a natural erection. Sildenafil is effective only when a man experiencing a natural sexual arousal, and when the sexual act is completed, the penis naturally returns to the relaxed state. In other words, sildenafil acts only on natural mechanisms of erection and this is its undeniable novelty and secret huge popularity.