Tadalafil (Cialis®) is another frequently prescribed impotence drug which is available in branded or generic form. It can be dispensed as generic Cilalis Oral Jelly to patients who have problems swallowing the medicine as a tablet. Tadalafil (Cialis®) needs to be taken before a man engages in sexual activity. It causes a greater amount of blood to go into the penis while a man is being aroused, allowing him to achieve and maintain an erection long enough to fully complete the sexual act.