Funny you should ask this now. I've just come off gabapentin after about 6 months, because I actually believe that although it was helping with pain and sleep, it was enhancing my fatigue and apathy. I'd been doing really well on Effexor (SNRI) for pain and Midodrine for my dysautonomia. A rough night would lead to breakthrough pain though so we tried adding gabapentin, just in the evenings for sedation and breakthrough pain relief. Initially it was great - I'd take it at the same time as the ambien and sleep right through the night.
However after about 3 months I started to feel very very low, and fluey in a way I hadn't experienced before. And I kept getting an infection inside my nose. Like an infected hair follicle, where your nose goes all red but the actual infection is inside the nostril. But this would finally disappear and then come back the next week! I was finding it harder and harder to get out of bed, and although my pain is currently (fingers crossed) at only a 3-4, every time we had evening plans I just lay on the bed and told him to go on his own. And weirdest, I'm quite thin - 140 pounds at 5ft 9, and I began to develop this enormous pregnant-looking tummy.
Long story short I happened to be chatting to a friend of mine who works in the prison system. I told her what I was taking and she shook her head - 'you need to get off that, really'. I was pissed, because as we all know, normal healthy people know ZERO about what we go through and what it takes to enable us to actually function. So I said 'Yeah, well...' But then she proceeded to reel off ALL my symptoms! The weight gain in the stomach (something to do with it eventually working like a steroid?) the constant infections, the lethargy, apathy.. she explained it's used widely in correctional facilities because it makes people less aggressive and more malleable. No shit.
Anyway, I've just realized this may seem like a downer post and if it does I'm sorry. It's just that I came off the gabapentin and within 10 days my stomach shrunk back to normal size and my apathy went away (although of course I still have the pain and the mac truck running back and forth over me all through the night, plus the molasses stuck to my carpets). For me, at least, what I thought was a rapid deterioration of the disease was actually just the effects of gabapentin. For the time being, at least. And if just one person can be helped by this story then it'll be worth the Debbie Downer post. I hope!