ROLE OF ENTEROCYTE IONIC EXCHANGES IN AMO XICILLIN INTESTINAL-ABSORPTION - EVALUATION THROUGH INTERACTION STUDY WITH AMILORIDE

Intestinal dipeptide carrier system has been shown in vitro to be invo lved in intestinal absorption of betalactam antibiotics. Given that ef ficiency of this transport system depends on a pH gradient (extracellu lar pH<intracellular pH) at the brush-border membrane of enterocytes, we assessed the effects of amiloride, a known inhibitor of the Na-H ex change, on the bioavailability of oral amoxicillin in eight normal vol unteers. Following a single 10 mg oral dose of amiloride, the absolute bioavailability of oral amoxicillin turned out to decrease by 27% (p< 0.01). The extent of reduction of oral amoxicillin AUC appeared to sig nificantly correlate (p=0.005) with the extent of decrease in potassiu m renal excretion but not with variations in antibiotic renal clearanc e under amiloride effect. Such patterns seem to confirm in vivo the ro le of the Na-H exchange in betalactam absorption and to suggest the un derlying regulatory function of intracellular Na concentration, the la tter depending on the (NaK)-ATPase activity.