@greg777 thank-you for posting this very interesting information. In scouring through a couple of pages of google links on the subject of pyridoxine vs pyridoxal-5'-phosphate as B6 sources, the gist of most articles are that P5P is the active form and therefore generally considered the best source of B6 but in this one In Vitro study that you reference they actually found that pyridoxine is not only less preferred but is actually toxic! I have been trying for a while now to hone in on a good B Complex supplement and with the latest wrinkle
regarding excessive B6 potentially exacerbating PN I switched from one B Complex supplement to a different one. In light of this new info I have already found what appears to be a better one here:
https://smile.amazon.com/Super-B-Complex-Methylated-Vitamins-Methylcobalamin/dp/B01787EPEE/ref=sr_1_8?dchild=1&keywords=b+complex&qid=1591463827&s=hpc&sr=1-8
This supplement contains only P5P as its source for B6 and also has good, absorbable sources for the other B components (e.g. methycobalamin for b12 rather than cyanocobalamin, etc.). Hopefully this will now enable us to take a higher dose of helpful B6 without the detrimental effects of pyridoxine.

Thanks again! Hank