In the presence of sexual stimulation, the inhibition of PDE5 leads to an increase in cyclic guanosine monophosphate (cGMP) levels. Elevated cGMP levels relax the smooth muscles in the blood vessels of the penis, allowing for increased blood flow.Avanafil and other PDE5 inhibitors are typically taken before anticipated sexual activity. The onset of action may vary, but they are known for their relatively rapid onset. The duration of action varies among individuals but generally lasts for several hours.