STUDIES ON THE MECHANISMS FOR INTESTINAL ABSORPTION AND RENAL EXCRETION OF QUINOLONE ANTIBACTERIAL AGENTS

Abstract

Transport mechanisms of intestinal absorption and renal excretion for new-quinolone antibactrial agents were investigated. The absorption of enoxacin (ENX) from rat jejunal loop exhibited a pH-dependent profile. The greater absorption at acidic pH of medium was observed, and ciprofloxacin (CPFX) reduced the ENX plasma concentration after simultaeously oral administration to rat. In the uptake experiments by the intestinal brush-border membrane vesicles (BBMV), initial rate and time-course of ENX and sparfioxacin (SPFX) were significantly dependent on the pH of medium (pH5.5 > pH7.5), and CPFX inhibited compleately the pH dependent uptake of ENX. The ion diffusion potential affected the uptake of these drugs by the intestinal BBMV. On the other hand, ENX uptake by the renal BBMV was contributed by not only the ionic diffusion potential but also the cation-H+ antiport system of organic cation secretion.