Here is a good summation about B6.

http://en.wikipedia.org/wiki/Vitamin_B6

When B6 builds up in a person, it is thought to be a result of poor conversion of pyridoxine to pyridoxal. This is mediated by riboflavin B2. If B2 is low then pyridoxal kinase cannot perform this task. So a person is actually "low" in active form and high in unconverted. Serum tests do not separate out this factor.

There has been a study on autistic patients showing that when NO supplements are taken, these patients show high serum levels or B6, just from food intake alone. Problems with conversion to active forms are suggested as an explanation for this.

Vitamin and mineral serum testing is rather confusing to doctors, who often do not interpret the results correctly. Very low levels are obvious and indicate deficiency, but normal or highs do not always reflect anything. Actual medical reports of B6 toxicity have been very few in number and have involved very high intakes, as the Wiki article states. There are unfortunately no lab ranges for people who take supplements listed. So anything you consume will test in a high range, most likely. I have yet to see lab ranges correlated with toxicities or intake. Most physicians just use symptoms to guide them.

However, just taking high doses of anything willy nilly, because of advertising or whatever, is not a good idea IMO. If you are not deficient, why bother? Emergen-C has alot of Vitamin C in it. That alone can cause problems in some people. It will change the pH of the urine, and affect all kinds of excretory needs. If that person is taking some RX drugs,it can delay excretion of them depending on the pH required for that task. High dose Vit C may also induce temporary acidosis in the blood, which then goes on to be neutralized by your buffering system. It has been shown that acidic conditions are present in pain situations. So the acid may be the trigger and not the B6 at all.

http://www.losethebackpain.com/treat...lsandpain.html

Here is a link explaining "pain":
http://www.spineuniverse.com/conditi...uropathic-pain

This has some nice graphics:
http://hubpages.com/hub/Physiology-of-pain