You can do permanent neurological damage by overdosing B6. It may sound hard to do but some energy drinks have several times your daily recommended intake and a lot of sports and fitness supplements put it in for no good reason. "Potentially hazardous" levels are defined as 1000% of your RDI over a prolonged period of time.
So if you have 2 white monsters, a multivitamin, a zinc/magnesium supplement and a rehydration tablet and you're there.