Metabolism of Tritium-Labeled Pyridoxine in Rats.

Urine, blood, and fecal samples from rats injected intravenously with tritiumlabeled pyridoxine hydrochloride were collected at various time intervals post injection for excretion and chromatographic study. Approximately 70% of the administered label was excreted in the urine in 5 hours. Fecal excretion was less than 0.03% in 96 hours post injection. There were 2 rates of excretion: the initial rapid rate with a half-time of about 45 minutes, followed by a slower rate with a half-time of 17 days. Chromatographic studies of urine showed that the pyridoxine was excreted primarily unchanged with a small amount of only one metabolite, most likely 4-pyridoxic acid.