PDE5A and erectile dysfunction: Phosphodiesterase 5 (PDE5) inhibitors such as sildenafil, vardenafil, tadalafil, andavanafil are commonly used for the treatment of erectile dysfunction and pulmonaryhypertension.1 PDE5 is an enzyme thatpromotes the breakdown of cyclic guanosine monophosphate in vascular smooth musclecells.