Zenegra 100 mg is a medication primarily used to treat erectile dysfunction (ED) in men. Its active ingredient is sildenafil citrate, a well-known PDE5 inhibitor that helps increase blood flow to the penis, enabling men to achieve and maintain an erection when sexually stimulated. Zenegra 100 mg typically starts working within 30 to 60 minutes after oral intake, with effects lasting up to 4 to 6 hours. The higher 100 mg dose is usually prescribed when a lower dose (such as 50 mg) is insufficient to produce the desired effect, but the exact dosage should be determined by a healthcare provider based on individual needs and tolerance.