TRANSPORT OF DRUGS ACROSS THE XENOPUS PULMONARY MEMBRANE AND THEIR ABSORPTION ENHANCEMENT BY VARIOUS ABSORPTION ENHANCERS

Purpose, The permeability of drugs across the Xenopus pulmonary membra ne and the effects of various absorption enhancers on their absorption were examined using an in vitro Ussing chamber technique. Methods. Ph enol red and fluorescein isothiocyanate-labeled dextrans (FDs) with di fferent molecular weights were chosen as water-soluble model drugs. Ab sorption enhancers used in this study were N-lauryl-beta-D-maltopyrano side (LM), linoleic acid-HCO60 mixed micelle (MM), sodium glycocholate (Na-GC), sodium caprate (Na-Cap), sodium salicylate (Na-Sal) and diso dium EDTA (EDTA). Results, The permeability of drugs gradually decreas ed with increasing their molecular weights, and the absorption of phen ol red significantly increased by these absorption enhancers. Among th ese additives, LM, MM and Na-Cap appeared to be more effective for enh ancing the permeability of drugs than the others. Furthermore, we plot ted the logarithm of apparent permeability coefficient (Papp) of these drugs against the logarithm of their molecular weights. There exists a good correlation between these parameters. We measured transmembrane resistance(Rm) of Xenopus pulmonary membrane during the transport exp eriment to examine the membrane integrity. The average Rm value was ab out 700 Omega . cm(2), and this value was maintained for 3 hr. Conclus ions. This method is useful for estimating the transport characteristi cs of drugs across the pulmonary membrane.