PHARMACOKINETICS OF TOLBUTAMIDE FOLLOWING INTRAVENOUS AND ORAL ADMINISTRATIONS IN RATS WITH OBSTRUCTIVE-JAUNDICE

The pharmacokinetics of tolbutamide (TB) following intravenous and ora l administration was compared between normal rats and rats with experi mentally-induced obstructive jaundice (OJ). The plasma concentration-t ime curve of i.v. administered TB was lower in rats with OJ, in compar ison with normal rats. The result of the pharmacokinetic analysis show ed no change in the elimination rate constant, but a significant incre ase in the volume of distribution in the OJ state. The increase in the volume of distribution of TB could be explained by the decreased prot ein binding in plasma. In the case of oral administration, the elevati on of the plasma concentration was slow and the plasma concentration p rofile was remarkably low in rats with OJ. The rate of TB disappearanc e from the small-intestinal lumen was delayed in the OJ state, and its marked accumulation in the tissues of the small intestine and the liv er was observed. This retarded uptake by the small-intestinal mucosa a nd subsequent pre-systemic accumulation might, at least in part, be th e reason for the slow appearance in the systemic plasma in the OJ stat e.