Zudena 100 mg is a medication used for the treatment of erectile dysfunction (ED) in men. The active ingredient in Zudena is udenafil, which belongs to a class of drugs known as phosphodiesterase type 5 (PDE5) inhibitors. Like other PDE5 inhibitors, udenafil works by increasing blood flow to the penis during sexual stimulation, helping men achieve and maintain an erection.