Fildena 100 purple pill treats erectile dysfunction, a medical condition in which the penis is unable to achieve a strong erection when the man is sexually aroused. This drug relaxes the blood vessels and helps increase blood flow to the muscles. It is advised to take this medicine one hour before planning intercourse to improve your sex life. The drug can also be used on an empty stomach. The effect of this medicine usually lasts for 3 to 4 hours.