Alprostadil
"At my urologists suggestion I used Edex today. 10 mg dose and injected the entire tube. I had a solid erection in about 5 minutes and it lasted for 3 hours. It went up much faster than it went down. So, it worked. Unfortunately it became quite painful, so much so that intercourse would not have been pleasureable. Doseage can vary from 1-40 mg so I will try again with a 2 or 3 mg dose. 

I had my prostate removed 2 years ago and haven't had a woody until today. I'm wondering if the pain is from the stretching of the tissues.  Some indication online that there is less pain with increased use. Viagra and Cialis did not work and I had crazy muscle pain with the later. So this is my likely last option."