My former psychiatrist (clinic, so they come and go) tried 300mgs x 3 daily as a "mood stabilizer." Its odd, really; I used to take Klonopin and "z" hypnotics and such, and I tolerated them just fine, but gabapentin threw me for a loop.

Now, I take 2 other anti-seizure drugs as "mood-stabilizers," but I have low-dose (100mgs capsules) gabapentin for as-needed use. I tolerate the low dose quite well. Since I don't need it very often, I sometimes take a couple of them at a time when I'm having trouble sleeping. Works quite nicely, a little bit of a hangover effect the next morning, but nothing too terrible.

I hope it helps you. I'm not able to tolerate higher doses, but some people swear by it. A friend of mine back in the day would pop my 300mgs capsules like they were candy, usually while getting stoned. Clearly, she was a big fan, lol.