I have always liked Cialis since it helps to regulate my BP as well but I can't afford it. My doc switched me over to Revatio (silendafil) 20MG (advised to take 1-3 daily). I haven't really noticed any differences since taking the Revatio. Does it take time to work like the Cialis and does it have to be taken every day? Yes, I tried the site sponsors stuff and it did nothing for me.