I know it's be quite a while since you posted, but I've recently found a good pain management practice here locally, and they've really been opening up my eyes.
Last week, they had me try a custom-compound cream to see if it helped with some of my nerve pain (it was a stabbing pain that started in my left "sit-down bone" and shot down the back & side of my leg to the knee. This pain has been occurring for a long time, and nothing has really helped it much, except heat, and heat isn't doing a lot of good any more.
The cream was a compound of ketamine & ketaphen, along with lidocaine and gabapentin gel - I was pretty skeptical, but it really does work well. The pain faded away almost immediately! I really like the fact that it isn't a systemic medication.
I guess my point is to keep searching. Good luck!