I used Gabapentin for four years, eventually I was taking 2400mgs per day but right from the very first day the side effects were horrible , I would feel terribly tired and my conversation suffered as I 'lost' words or my sentences faded away and I never finished them. My Pain Consultant suggested changing to Pregabalin/Lyrica and I am like a new woman. I have much more energy and conversation is much easier - I would say my brain is sharper, no more brain fog.
Also I only take 600 mg per day in the form of four tablets so you wouldn't forget .