I took neurotin (gabapentin) for a while, and got nearly NO relief - it made me feel... odd and foggy. Stopped that and went to Lyrica- I didn't notice weight gain, but I did have an allergic reaction to it, so I stopped it. I had been getting some relief from it. Started taking Keppra - Levetiracetam 500mg 2x, 1000mg 1x. It helps me more than the neurontin. I don't notice the relief unless I miss a dose.
I have taken Mirapex for migraines several times over the last 4 months. The only problem with that (and this WORRIED me) is the major side effect- rebound headaches. If you take it too often, you will actually wind up with more headaches. Fyi.
I haven't (knock on wood) noticed side effects from pain medication. I will occasionally feel fuzzy, but thats really it.