Prediction of skin permeation of flurbiprofen from neat ester oils and their O/W emulsions

Abstract

Although many in silico models were reported to predict the skin permeation of drugs from aqueous solutions, few studies were founded on the in silico estimation models for the skin permeation of drugs from neat oil formulations and o/w emulsions. In the present study, the cumulative amount of a model lipophilic drug, flurbiprofen (FP), that permeated through skin was determined from 12 different kinds of ester oils (Qoil) and an in silico model was developed for predicting the skin permeation of FP from these ester oils. Thus, the obtained Qoil values were well predicted with the FP solubility in the oils (Soil), the amount of FP uptake into the stratum corneum (SCoil) and molecular descriptors of dipolarity/polarizability (π2 H) and molecular density. This model suggests that the thermodynamic activities of FP both in the formulations and skin are the key factors for predicting the skin permeation of FP from the ester oils. In addition, a high linear relationship was observed in the double-logarithm plots between the Qoil and the cumulative amount of FP permeated through skin from 20% ester oil in water emulsion (Qemul20%). Furthermore, the skin permeations of FP from 5 and 10% ester oil in water emulsions, Qemul5% and Qemul10%, respectively, were also predicted by the horizontal translation of the y-axis intercept of the liner equation for the relation between the Qoil and Qemul20%. These prediction methods must be helpful for designing topical oily and/or o/w emulsion formulations having suitable and high skin permeation rate of lipophilic drugs.