A single Fildena 100 tablet or oral tablet has an ideal duration of about 4 hours after its activation period ends. This is because the drug Sildenafil Citrate, which is the core of the Fildena 100mg oral tablet, remained effective in the body after activation for about 4 hours. A single dose of Fildena 120 Oral Tablet containing Sildenafil Citrate needs about 60 minutes maximum to get ready or activated for it to work. Regardless of the strength of the dose, Sildenafil Citrate will only work after the introductory period is over.