Men who struggle to keep their penis hard during sexual activity and to keep it that way for extended periods of time may be suffering from erectile dysfunction. Each of these men has been prescribed vidalista 10 mg by the doctor as a course of treatment. Tadalafil, the primary ingredient in this PDE-5 inhibitor medication, helps men with weak erections sustain a hard erection during sexual activity. Vidalista works best when taken on the weekends because it takes the body 36 to 48 hours to feel its effects.