The effects of Filitra 40 mg are similar to other PDE5 inhibitors and typically last for about 4 to 6 hours. Sexual stimulation is necessary for the medication to be effective. Vardenafil inhibits the enzyme PDE5, leading to increased levels of cyclic guanosine monophosphate (cGMP). This, in turn, relaxes the smooth muscles in the blood vessels of the penis, allowing increased blood flow and facilitating an erection.