There are many medicines available in the market today for the treatment of a disease called erectile dysfunction and it is also giving very good results to the people. So you buy a Fildena 25 tablet. The drug contains sildenafil citrate as a generic brand. So the effect of this drug lasts for 4 to 6 hours. And if the effect of this medicine lasts for more than 6 hours, seek the help of a doctor immediately.