I spent an inordinate amount of time searching goggle scholar as well. I could find nothing with relation to gabapentin.

What I did find was more mentions of B5 being used to treat neuropathy than I have seen before, e.g.

Pantothenic Acid

Supplements That Help Treat Neuropathies (Part 1)

My understanding to date is that while B5 deficiency is rare, it sometimes manifests as burning feet syndrome which usually does respond to B5 supplementation (I've seen 250 - 500 mg/day mentioned more than once).

Other than that, I have usually seen it mentioned as an adjunct to R-Lipoic Acid (RLA) in treating diabetic peripheral neuropathy. Since RLA worked so well for me (despite all testing for diabetes being negative) I tried it anyway, and in my case it has helped more than RLA alone (mostly in reducing the zaps and jabs).

For other types of neuropathy, or without RLA, I do not know, but as there is no tolerable upper level intake, I don't see any harm in giving it a try.

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FWIW, my wife takes a low dose of gabapentin for nerve pain in her shoulder. She also has severe tinnitus. She tried a combination supplement made up of inositol, choline, & B5 for the tinnitus, and it has helped some. Since it was so expensive that way, she now buys & takes those components separately (and tinkers with the mix). With the small dose (100 mg) of gabapentin she takes, if the B5 were cancelling it out I think she would definitely notice it, and her pain level increase. It hasn't.

Doc