Sildenafil acts as the active ingredient in the Silagra drug. Silagra is taken 1 hour before intercourse, after which it lasts for 4-5 hours. Consult a doctor before taking Silagra. Silagra is one of ED's best tablets. Silagra is one of the best tablets for men to use. That is why women and children use this drug. Sildenafil Is Great For Sex Time.