Bamirastine hydrate

The role of P‐glycoprotein (P‐gp, ABCB1) on the absorption process was investigated by drug–drug interaction studies of TAK‐427 with P‐gp inhibitors (erythromycin, ketoconazole or quinidine) in rats and by transport studies using rat multidrug resistance (MDR1) stably expressing cells and rat small intestine mounted in a Ussing‐type chamber. TAK‐427 showed high efflux activity with low permeability in rat MDR1a and MDR1b stably expressing cells and was revealed to be a typical substrate for P‐gps. Although TAK‐427 was mainly absorbed from the small intestine in rats, a large part of the dosed compound remained in the gastrointestinal tract. Orally co‐administered P‐gp inhibitors (50 mg/kg) increased theAUCof TAK‐427 after a 5 mg/kg oral dose 5.4‐ to 18.3‐fold, whereas orally administered P‐gp inhibitors had a minor effect on the increase in theAUCof TAK‐427 (1.3‐ to 2.2‐fold) after a 0.5 mg/kg intravenous dose. Thus, the bioavailability of TAK‐427 after oral administration in rats (7.3%) markedly increased when co‐administered with P‐gp inhibitors (28.6–57.6%). Moreover, the transport of TAK‐427 was predominantly secretory throughout the rat small intestine and was inhibited by P‐gp inhibitors. In conclusion, P‐gp can markedly reduce the absorption of a typical P‐gp substrate by its efflux activity throughout the absorption site. Copyright © 2008 John Wiley & Sons, Ltd.