Gabapentin does not require a build up in your system. It acts based on dose. 300 mgs is a very small dose. I have taken as much as 1200 mgs before bed. My usual dose is 900 mgs, 1 and 1/2 600 mg pills. I am 180 pounds. Ask your doctor about trying 600 or even 900 mgs. There are no noticeable side effects. It has a short half life, 8 hrs, so there is little in your system the next day.

My best to you.