I've been on gabapentin for about three years, mainly to get rid of the "pin-prick" or "electric shock" type pains (2 x 300 mg capsules, 3 times daily). When I started to wake up with pain all down my left side, my MS Nurse suggested upping the night-time dose to 3 X 300 mg - and this sorted the pain out. Early this year, the amount of general pain had increased, and the Neurologist said that I could go up to 3 x 300 mg, 3 times daily - when I could not cope with the pain. I was able to put this off until mid May, and then I upped the dose over a couple of days.
Now, I am getting extreme fatigue problems, particularly the lower legs, which is annoying as this wipes out some of the benefit of the FES. A phone-call to the MS Nurse resulted in a very quick response: cut the Gabapentin back a little toward the old level and see what happens to the fatigue. "Gabapentin can lead to fatigue problems".
It is too soon to say what the result is - I need a good two hours on my feet (and my sticks) to be sure - and there is always the reverse of the placebo effect to be considered: sort-of "I should feel better so I do feel better". But seriously, I do feel better, not a lot, but enough to say that the Gabapentin increase could have been responsible.
Up until the last few months, I thought it was wonderful, but it starts to look like I hit a threshold. What I would say is not to make any changes without talking to your MS Nurse, or Neurologist, or at the least, a pharmacist. I did not notice any problems building up to the 600mg, 600 mg, 900mg, level. It does look like the last little bit took me over the top (so to speak).