Fildena is a medication primarily used to treat erectile dysfunction (ED) in men, with the active ingredient being sildenafil citrate. Sildenafil is the same active ingredient found in the brand-name drug Viagra. It is available in various strengths (e.g., 25 mg, 50 mg, 100 mg) and works by increasing blood flow to the penis, which helps achieve and maintain an erection when sexually aroused.