Modulation of the p-glycoproein-mediated intestinal secretion of glibenclamide: in vitro and in vivo assessments.

The everted gut sac method was used to assess the role of the P-glycoprotein (P-gp) on the intestinal secretion of glibenclamide, a prototype of drug used to treat diabetic mellitus. The study included the evaluation of a P-gp modulator carbamazepine used at equimolar doses in the rat. Furthermore, the influence of carbamazepine on the disposition kinetics of glibenclamide in plasma was characterized. For the in vitro experiments, ileal sacs were incubated with glibenclamide in the presence or absence of carbamazepine. In the in vivo experiments, albino rats of either sex were randomly allocated to two groups (n = 6) and oral treatment with glibenclamide (3.6 mg/kg), alone and coadministration with carbamazepine (90 mg/kg). Blood samples were collected at an interval of 1, 2, 4, 6, and 8 h, respectively. Glibenclamide concentrations in both in vitro and in vivo samples were estimated by a sensitive RP-HPLC method. The rate of glibenclamide accumulation in the intestine wall of everted sacs was significantly lower after its incubation with carbamazepine when compared to glibenclamide alone treated. In the agreement with the in vivo and in vitro experiments, the presence of carbamazepine induced an enhancement in the concentrations of glibenclamide in plasma and gastrointestinal tract. The results obtained in this study, both under in vivo and in vitro conditions confirm the relevance of P-gp-mediated transport to the intestinal secretion of glibenclamide.