<prompt> Which of the following agent is not used for treatment of erectile dysfunction?PGE1VardenafilPhenylephrineAlprostadil  <response>: for male impotence: AlprostadilPG E1 injected into the penis causing an erection lasting for 1-2 hrs oral sildenafiltadalafil can also be given papaverine, yohimbine can be used though rarely ESSENTIALS OF MEDICAL PHARMACOLOGY;7TH EDITION; KD TRIPATHI; PAGE NO 190 