What Are The Side Effects Of Neurontin?

I have been on a high dose of Neurontin (2400mg/day) for 5 years now following a severe motor vehicle accident that left me with severe neuropathic pain from a badly broken pelvis. My SI joint was broken and I have had 2 surgeries to fix so have not been able to lower my dose. I am inquiring about long term use of this drug and would like to use marijuana as an alternative drug to help me wean off the gabapentin as it seems to give me much of the same pain relief and I am worried about the long term effects of Neurontin. My question is regarding the long term effects of Neurontin and how it is going to effect me in the future?