I also take the R-Lipoic 100mg/day, but can't say whether it has been effective or not.
Along with CoQ10 and Fish Oil and a few others, I seem to be able to maintain a tolerable PN pain level and not progress..... altho my recent heel spur kinda set me back, a bit. I stopped taking the Chondroitin/Glucosamine.... because the heel spur seemed to occur about a month after starting it. My wife takes it and says it helps, but its made of shellfish and oyster shell - calcium, and a bone spur is excess..... calcium/bone..... so I've held off of it, until the problem settles down.