I have noticed that everytime I try to increase my Neurontin above 600mg I get the following reactions: my heart rate goes up to 170+ and becomes erratic, enough to make me feel as though i will faint. I was driving one day when this happened, and I thougt I would pass out at the wheel. This reaction is hard to describe, but it feels like having a a really bad throbbing headache throughout my skin. It gets unbearable. When I reduce the dose back to 600mg it gets bearable. But it is still there. I am wondering if anyone has had this reaction. It is my main med for pain, but it seems to be increasing it. I have verified this reaction by going back and forth between the 600mg and upping it to 1200+ then reducing it again. Any help would be appreciated.....