Fildena 25 is a generic form of sildenafil that functions as a phosphodiesterase type 5 (PDE5) inhibitor. It helps men with erectile dysfunction achieve and maintain an erection suitable for sexual activity by increasing blood flow to the penis during sexual stimulation. Compared to some other ED drugs, Fildena 25 has a longer half-life; its effects might linger for up to 36 hours. It is interesting to observe that sexual arousal is necessary for the drug to function.