The purpose of this study was to examine concentration-dependent effects of Azone® (AZ) on the buccal absorption of diazepam (DIAZ). Porcine buccal mucosa was placed in modified Ussing chambers and pretreated with 10 μL of 0%, 5%, 20%, and 50% (w/v) AZ in ethanol. DIAZ was administered to the donor chamber either in solution or a chitosan-based gel. The donor chamber disappearance, receptor chamber appearance, and tissue retention of DIAZ were monitored over 2 h by HPLC, with AZ tissue disposition also measured by liquid chromatography-mass spectrometry profiling of tissue cryosections. DIAZ steady-state flux values significantly (p