Fildena 25 mg contains Sildenafil Citrate, which is a PDE5 inhibitor used primarily to treat erectile dysfunction (ED). The half-life of Sildenafil is approximately 4 to 5 hours.

Half-life is the time it takes for the concentration of a drug in the blood to reduce by half. For Sildenafil:

Peak Plasma Concentration: Fildena 25 mg reaches peak plasma concentrations in about 1 to 2 hours after oral administration.

Duration of Action: The effects of Fildena 25mg typically last for about 4 to 6 hours, which is why it's often recommended to take it about 30 minutes to 1 hour before sexual activity.

This half-life means that Sildenafil is metabolized and cleared from the body relatively quickly, which can influence how often it needs to be taken and the duration of its effects.