Click Here To buy Now Fildena 100 is a medication used to treat erectile dysfunction (ED). Its active ingredient is sildenafil citrate, which is also the active ingredient in . It works by increasing blood flow to the penis, helping to achieve and maintain an erection when sexually stimulated. The effects can last for up to four hours, but it doesn't cause an erection without sexual arousal. Common side effects can include headaches, flushing, nasal congestion, and digestive issues. More serious side effects, though rare, can include vision changes or priapism (a prolonged and painful erection).