Zenegra 100 mg is a prescription medicine commonly used to treat erectile dysfunction (ED) in adult men. It contains sildenafil, a phosphodiesterase type 5 (PDE5) inhibitor. Sildenafil increases blood flow to the penis during sexual stimulation, helping achieve and maintain an erection. The 100 mg strength may be prescribed when a lower sildenafil dose does not provide an adequate response and is tolerated. However, 100 mg is generally the maximum recommended sildenafil dose for ED in a 24-hour period. It is not necessarily the appropriate starting dose for every person, and you should never increase your dose without medical advice.