Well, I'm not sure if any one else cares, but I just found the bit about P5P, quite by accident...I had emailed it to myself some time ago and was clearing out my inbox...
Quote:
Safety, Toxicity, and Side Effects
The use of supplemental P5P has not been associated with toxicity, although the inactive form, pyridoxine, has been associated with reports of peripheral neuropathy.[45] One hypothesis is that pyridoxine toxicity is caused by exceeding the liver's ability to phosphorylate pyridoxine to P5P, yielding high serum levels of pyridoxine which may be directly neurotoxic or may compete with P5P for binding sites, resulting in a relative deficiency.[46]
Mpofu et al reported electrophysiological and neurological examination of 17 homocystinuric patients who had been treated with 200-500 mg pyridoxine HC1 daily for 10-24 years, and found no evidence of neuropathy.[47] Most reported cases of neuropathy associated with pyridoxine supplementation have involved intake of at least 500mg/day for two years or more.[48] While there is no doubt that vitamin B6 can be neurotoxic in gross excess, there is considerable controversy over the way in which toxicological data have been translated into advised limits.[8]
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http://www.findarticles.com/p/articl..._6/ai_71948217