Zenegra 100 Tablet is a prescription medicine that contains Sildenafil and is used to treat erectile dysfunction in men. It works by increasing blood flow to the penis. This helps men to get or maintain an erection. Erectile dysfunction (also known as impotence) is a sexual condition where a man cannot sustain a hard erected penis which is required for normal sexual activity. It happens due to decreased blood flow to the penis which is caused due to narrowing of the blood vessels supplying the penis. It belongs to a group of medicines known as phosphodiesterase type 5 (PDE 5) inhibitors.