Yes, I was also on 3600 mg of neurotin for a couple of years. I was switched to Lyrica, and I have to say that it is better for me. The doc did put me on 150 mg. of lyrica, any less than that was not working as well. I am glad I made the switch.
As for weight gain I am not sure, I have put on a couple of pounds in the past 6 months but, I don't get the physical exercise I use too either and it is cold so I have not been out as much. So, I am hoping that once the weather gets better I will be more active and lose the few extra pounds I have gained.