Tadalafil
"I'm 75 and have been taking high blood pressure medicine for about 7 years.  About 5 years ago I started to experience problems maintaining an erection during intercourse.  At that time I started taking Cialis (10 mg) and it worked for me right away.  However, about two years ago, I found that 10 mg was not enough for me to maintain an erection long enough to complete intercourse.  That is when I began to increase the dosage in 5 mg steps until I reached the point where I could feel its effects for a full 36 hours.  I am now at 25 mg and it is working fine. It's effect usually lasts 40 hours or so.  Erection is hard, like it was 50 years ago.  Sometimes a mild headache, but not bad enough to stop me from using Cialis."