Neural modulation of cephalexin intestinal absorption through the di- and tripeptide brush border transporter of rat jejunum in vivo.

Intestinal absorption of beta-lactamine antibiotics (e.g., cefixime and cephalexin) has been shown to proceed through the dipeptide carrier system. In a previous study, nifedipine (NFP), an L-type calcium channel blocker, enhanced the absorption of cefixime in vivo but not in vitro, and it was suggested that neural mechanisms might be involved in the effect of NFP. The aim of the present study was to assess the involvement of the nervous system on the intestinal absorption of cephalexin (CFX). To investigate this, we used a single-pass jejunal perfusion technique in rats. NFP and diltiazem enhanced approximately 2-fold the plasma levels of CFX in treated rats versus untreated controls. NFP also increased approximately 2-fold the CFX level in portal plasma and increased urinary excretion of CFX, thus indicating that CFX did effectively increase CFX intestinal absorption. Perfusing high concentrations of dipeptides in the jejunal lumen competitively reduced CFX absorption and inhibited the enhancement of CFX absorption produced by NFP. Hexamethonium and lidocaine inhibited the effect of NFP, whereas atropine, capsaicin, clonidine, and isoproterenol enhanced CFX absorption by the same order of magnitude as NFP. Thus, complex neural networks can modulate the function of the intestinal di- and tripeptide transporter. Sympathetic noradrenergic fibers, intestinal sensory neurons, and nicotinic synapses are involved in the increase of CFX absorption produced by NFP.