Fildena Chewable 100, as a accepted sildenafil drug, works as a selective PDE5 antagonist, this means that it stops the secretion of an enzyme referred to as PDE5 (phosphodiesterase). This mechanism of sildenafil allows the body to stop degrading a chemical known as cyclic Guanosine Monophosphate (cGMP). With this enzyme-chemical interplay, your body releases a substance known as nitric oxide when you are sexually inspired.