Fildena Double is an oral treatment; it contains a PDE5 inhibitor drug called Sildenafil citrate. This potent ED drug works on the enzymatic level. It stops the PDE5 enzyme from reducing cyclic Guanosine Monophosphate levels in your body. When the cGMP levels increases, nitric oxide, and cGMP relax muscles and dilate arteries. This reaction augments higher blood flow in the male organ. Later, when a man is sexually stimulated, he attains an erection.