I can't give you the medical reasons why, but almost everyone that I have spoken with that has been diagnosed with RSD reacts differently to different meds. I have been on lyrica for about 6 months now. I was taken off of neurontin and put on the lyrica, and the lyrica has worked much better with much less side effects. By now I am probally addicted to it, but with the pain I experience you get to the point where being addicted to a medication doesn't matter, only the slight relief that you can feel.