A generic form of the drug Viagra, used to treat erectile dysfunction (ED), is called Fildena 25 mg. Since it is an inhibitor of phosphodiesterase type 5 (PDE5), it acts by boosting blood flow to the penis. This aids in the erection and maintenance of males. The half-life of Fildena 25 is typically about half an hour, but it can take up to an hour. Up to four hours may pass between the effects. It is recommended to take Fildena 25 orally, either with or without food. It is often taken half an hour before engaging in sexual activity. Men who are allergic to Fildena should not take 25 mg of it.