Zenegra 100 mg is a medication used to treat erectile dysfunction (ED) in men. It contains sildenafil citrate as its active ingredient, which works by increasing blood flow to the penis, enabling a man to achieve and maintain an erection during sexual stimulation. The effects of Zenegra 100 mg can last for up to 4 hours. During this time, men may find it easier to achieve and maintain an erection sufficient for sexual activity.