Permeability of human intestinal mucosa using a continuous flow-through perfusion system

Continued interest in in vitro methods for performing bioavailability/bioequivalence (BA/BE) studies for drug registration purposes, prompted us to investigate the suitability of a continuous flow-through perfusion system to determine diffusion of a wide variety of permeants, through human intestinal mucosa. Permeability of fresh and frozen intestinal mucosa towards water, 17beta-estradiol, sumatriptan, arecoline and vasopressin was compared. Furthermore, diffusion studies of water, sumatriptan, arecoline. arecaidine, estradiol cyclosporin and vasopressin across frozen/thawed intestinal mucosa specimens ( - 85 degreesC) were performed. No statistically significant differences between the flux values of the five compounds tested across fresh and frozen intestinal tissue, were found. Furthermore, it was demonstrated that the flux rates of the various compounds across these tissues decreased with increasing molecular size. However, the flux rates across frozen intestinal mucosa for compounds with molecular weights > 300 Da, were low. Flux rates for the compounds studied across frozen/thawed human vaginal and buccal mucosa were 36-160% higher than those across frozen intestinal mucosa. We concluded that the continuous flow-through perfusion system used shows promise as an in vitro method for permeability determination through intestinal mucosa. However, other human mucosa e.g. vaginal mucosa. may have to be considered as alternatives to intestinal mucosa if therapeutic agents with molecular weights > 500 Da are to be compared for in vitro BA/BE purposes, and further studies in this respect are warranted. (C) 2002 Elsevier Science B.V. All rights reserved.