If the Trimix is failing, you can always go to Caverject or Edex which is straight Alprostadil. I started with Caverject Impulse (not available now until summer 2010) then the pharmacy switched me to Edex. Both worked great but I also had the aching pain. 40 ml of either one will give most men a 4 hour erection that is so hard that you can't believe it.
I went through the 4 hour experiences and aching pain, so my urologist switched me to Trimix. It has been working fine, anywhere from a one to two hour erection. And no pain. I don't take an ED drug before. Just the injection and it works in 5 minutes.