Fildena 100 is a medication used for the treatment of erectile dysfunction (ED), a condition characterized by the inability to achieve or maintain an erection sufficient for sexual activity. The active ingredient in Fildena 100 is sildenafil citrate, a phosphodiesterase type 5 (PDE5) inhibitor. This drug works by relaxing the smooth muscles in the blood vessels of the penis, allowing increased blood flow to the area when sexually stimulated.