The active ingredient of Filagra, a drug used to treat erectile dysfunction (ED) in men, is sildenafil citrate, which is also included in Viagra.  It works by suppressing the enzyme phosphodiesterase type 5 (PDE5), which improves blood flow to the penis during sexual stimulation, helping to create and keep an erection.  Depending on the demands of each individual, Filagra comes in a variety of forms and strengths, such as oral jelly and tablets.