Buccal drug absorption. II: In vitro diffusion across the hamster cheek pouch.

The in vitro diffusion of a series of substituted acetanilides across the hamster cheek pouch was studied. The keratinized epithelial layer of the cheek pouch appeared to provide the major barrier to diffusion of these compounds. Linear relationships were found for plots of log epithelial permeability (Pe) versus the log of the octanol-buffer partition coefficient (PCoct; r = 0.712), and log Pe versus the log of the isooctane-buffer partition coefficient (PCiso; r = 0.869). Comparison of the in vitro data with in vivo data obtained in humans using the buccal absorption test showed good correlation (r = 0.878) between Pe and percent buccal absorption in 5 min. These results suggest that diffusion across the hamster cheek pouch may have some utility in the prediction of human buccal absorption.