Pyridoxine is always simultaneously administered orally with
isoniazid for
tuberculosis patients in the clinic to prevent or treat the nervous system side effects induced by
isoniazid. So the aim of this research was to investigate the effects of
pyridoxine on the intestinal absorption and pharmacokinetics of
isoniazid. The intestinal absorption of
isoniazid with or without
pyridoxine was investigated by the rat single-pass intestinal perfusion model in situ, and a high-performance liquid chromatographic method was applied to study the pharmacokinetics of
isoniazid with or without
pyridoxine. The results suggested that the intestinal apparent permeability (P app) and intestinal absorption rate constant (K a) for
isoniazid (30 μg/ml) were decreased by 43.7 and 36.4 %, respectively, by co-perfused
pyridoxine (40 μg/ml). In vivo, the effect of
pyridoxine on
isoniazid pharmacokinetic correlated with the doses of
pyridoxine. The blood concentrations of
isoniazid at the absorption phase were affected by co-administered
pyridoxine, but the AUC and C max of
isoniazid were not greatly affected by
pyridoxine as expected from the inhibition by
pyridoxine of the intestinal absorption of
isoniazid, which could be caused by its rapid absorption phase. Therefore, although the intestinal absorption of
isoniazid could be significantly inhibited by
pyridoxine, the pharmacokinetics of
isoniazid oral administration was not greatly affected by the decreased intestinal absorption of
isoniazid due to its rapid absorption.