Fildena Double  is a medicine containing sildenafil citrate, which is mainly used to treat erectile dysfunction (ED) in men. Sildenafil belongs to a class of medicines called phosphodiesterase type 5 (PDE5) inhibitors. The basic effect of Fildena Double 200 mg is the effect on the cardiovascular system. It works by blocking the PDE5 enzyme, which increases levels of cyclic guanosine monophosphate (cGMP) in blood vessel smooth muscle.This relaxation of blood vessels allows for increased blood flow to the penis, which improves erection.