| Popis: |
This chapter describes biological and physicochemical parameters which determine the rate and extent of chemical penetration across human skin. It discusses how these parameters interact with the physicochemical properties of the dermally contacting chemical to determine the kinetics and degree of penetration. When the skin is treated with volatile solvents, the barrier to chemical transport is reduced, presumably because of lipid extraction. If the chemical is in a solid state then the particle size and polymorphism of the material may contribute to the kinetics of this first step in absorption. Chemicals which are extremely lipophilic will be severely rate limited by this process due to their low solubility in the viable tissue and the resultant slow interfacial transfer kinetics at the lipid-aqueous boundary. It is possible that certain chemicals may induce significant changes in cutaneous blood flow. For a topically applied chemical to reach the systemic circulation requires that it transports through both lipophilic and aqueous regions. |
