I started on the Gabapentin at the end of June, neuro prescribed 300mg am and pm.
Started of taking it at night initially for my system to get used to it, made me feel a bit zonky at first but after a week or so i was grand. I take it at the same time as my amitriptyline about 1-2 hrs before bed.
Then began to introduce the morning dose, made me a bit zoned out the first day so rang MS nurse who recommended that i get my GP to prescribe it as 100mg capsules so i could titrate up gradually to the 300mg dose neuro had advised. I am on the 300mg now am&pm and find it great for pain.
Like you i was changing my DMD around the same time, moved from Rebif to Avonex so good to get stabilised on one before introducing another if that is possible so you know how/what meds are affecting you.
Hope this helps