Seek medical advice before taking Fildena. Sildenafil acts as the active ingredient in Fildena drugs. Fildena is taken some time before intercourse. With this, you can have sex for a few hours i.e. up to 8 hours. Fildena is used to solve the problem of ED. There are a few things to keep in mind after taking Fildena. Do not drink and drive indigestion while taking tablets such as alcohol.