Erectile Dysfunction
"At 20mg, Cialis has no effect anymore.  However, when taking 2-20mg pills at the same time, I have the same effect as 1 Viagra except for a 36 hour period.  I would consider continuing with Cialis if a 40 mg pill was available.  I am 57 years old.  This may account for the lack of effect by the standard pill.  Taking 2 Cialis would not be cost effective."