BACKGROUND: The role of stratum corneum has been known to be the major barrier against percutaneous absorption. The change of osmotic gradient onto stratum corneum may affect the permeability barrier function though its mechanism has not been explained. OBJECTIVE: In this study, we have tested hyperosmolar glucose solution (1M, 0.1M) over the living skin or the separated epidermal sheets to determine the penetration-related pharmacokinetics such as absorption, saturation, diffusion kinetics in vivo or in vitro. METHODS: The hyperosmolar glucose patches were applied to 10 healthy volunteers' forearm skin to analyze the absorption profiles through stratum corneum. For investigating the role of osmotic pressure influencing the disposition of glucose, in vitro two compartment model was used to characterize the pharmacokinetics of glucose through epidermal sheets. RESULTS: The quantitative assay of applied hyperosmolar glucose from sequentially stripped stratum corneum of volunteers revealed the high glucose/protein ratio and steep concentration gradient at the uppermost layers down to lower layers. The pharmacokinetic profile of hyperosmolar glucose in vitro shows both the saturation delay pattern and steady flux pattern regarding glucose diffusion. CONCLUSION: The stratum corneum act as a major permeation barrier against glucose disposition, though the concentration-dependent pharmacokinetics by its osmotic gradient were rather different. Thus, the osmolarity-related event over stratum corneum might be a considerable factor during percutaneous absorption.
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