Abstract
The effect of various oil vehicles on the skin penetration of materials with a high molecular weight and high lipophilicity, which are properties that are inappropriate for skin penetration, were investigated under finite dose conditions. We evaluated stearyl glycyrrhetinate (SG) and the fluorescent dye DiI (high molecular weight (723 and 834 Da, respectively)). SG was saturated in 14 different vehicle oils and applied under finite dose conditions (2.5 μL/cm2) to Yucatan micropig skin in vitro. The relationships between the amount of SG in the skin and the physicochemical properties of the vehicle oil (molecular weight, viscosity, surface tension, IOB value, and solubility of SG in the oil) were analyzed via multiple regression analysis. The molecular weight and surface tension of the vehicle were explanatory variables for the skin penetration of SG: the skin penetration of SG increased as the molecular weight and surface tension of the vehicle decreased. DiI exhibited results that were similar to those obtained for SG. Under finite dose conditions, some of the physicochemical properties of the vehicle (low molecular weight and surface tension) affected the penetration of compounds with characteristics that are inappropriate for skin penetration.
