Erectile dysfunction is a medical condition that affects the ability of men to have an erection. It is also known as impotence or the inability of men to achieve a satisfactory erection. How does Fildena 25 work? You take this tablet 30 minutes before having sexual intercourse. You can take it before or after having a meal. You take it with water but don’t break or chew it. You shouldn’t take it with alcoholic drinks or fatty foods. You should take it as directed by your doctor.