Sildenafil 100 mg, commonly used to treat erectile dysfunction, typically lasts for about 4 to 6 hours after taking the dose. Its effects usually begin within 30 to 60 minutes, especially when taken on an empty stomach. During this time, sexual stimulation is still required to achieve an erection. While the drug remains in the body for several hours, its effectiveness gradually decreases over time. Factors like age, metabolism, diet, and overall health can influence how long the effects last. It is important not to take more than one dose in 24 hours and to follow your doctor’s instructions carefully.