Fildena 100 is a medication used to treat erectile dysfunction (ED) and contains 100 mg of sildenafil citrate, the same active ingredient found in Viagra.The standard dose for Fildena 100 is 100 mg, taken orally about 30 to 60 minutes before sexual activity. It is typically used when a lower dose, like 50 mg, is not effective.Sildenafil works by increasing blood flow to the penis, which helps achieve and maintain an erection in response to sexual stimulation. The effects usually last for about 4 to 6 hours.