Neurontin has been a much discussed topic on here since I joined. First day of detox, which was almost 5 months ago, I started on 2400 mg daily. Stopped it for a few weeks then back on it. The side effects you describe sound pretty much what I experienced. A fog with confusion, vision, and a crazy anxiety that almost seemed like hallucinations. I even called my counselor about the panic feelings and he told me he (himself) experienced the out of body feelings. I felt weird. Now, I'm still taking it, only 900mg. Everything is fine now. This is how Neurontin/Gabapentin affected me only. This pill seems to be a popular doctor remedy in people getting clean. You absolutely feel out of it a bit. If you don't like it, I say tell your doctor. You do have to taper it down, so be careful.. Hope this helps you. Take care and post back how you are doing.
Trembling/shaking, delusions, dementia - all listed in the side effects of Gabapentin on Drugs.com. I took it for a short period of time for nerve damage and all it did was make me tired...I wasn't on it but 5 or so days so I stopped taking it. If I were you I would call your Dr's office.
Wishing you good luck!