This drug, like the small blue pill of Viagra, has different ways of influencing the human body and most often depends on it. On average, Cenforce users feel the effect of the drug for 4 hours after taking it. There is a separate group of men who experience an erection instantly after taking it. It also happens that users feel a headache or some spasms from Cenforce, but these, like other possible symptoms, are minor and go away on their own after a couple of hours.