Sildenafil citrate is the main ingredient of Fildena 100 and is also the most widely used. This medication relaxes blood vessels and promotes smooth blood flow within the male genitals, especially the penile region, by blocking the PDE5 enzyme. The blood flow to the male genital region's erectile region is decreased by this specific enzyme. cGMP activation leads to an increase in nitric oxide synthesis. This causes an enzyme to become inactive, improving blood flow to the male genitalia and, ultimately, the entire penile erection mechanism.