I used Cialis but now taking 20mg of it I feel no effect anymore. When I take 2 pills of 20mg each at the same time, I have the same erection as I take 1 Viagra pill. I would continue with Cialis if a 40 mg pill were available. I am 63 years old. This may be the reason of the poor effect when taking the standard dose. But using 2 Cialis is not price effective.