ESTIMATING SKIN PERMEATION - THE VALIDATION OF 5 MATHEMATICAL SKIN PERMEATION MODELS

This study provides an analysis of the reliability of five mathematica l models, simulating permeation of substances through the skin from aq ueous solutions. An extensive database was generated, containing data on 123 measured permeation coefficients of 99 different chemicals and their physicochemical properties. In addition, in this database all re levant experimental conditions are included. The coefficients of the d ifferent skin permeation models were estimated by non-linear multiple regression, using the octanol-water partition coefficient and the mole cular weight as independent parameters. The reliability of the models was evaluated by testing variation of regression coefficients and of r esidual variance for subsets of data, randomly selected from the compl ete database. Three models were considered to provide reliable estimat ions of the skin permeation coefficient. These are based on the McKone and Howd model, the Guy and Potts model and the Robinson model. The l ast-mentioned two models were adaptations, because MW(0.5) as independ ent parameter provided a better fit than MW (MW=molecular weight) in t he original models. The McKone and Howd model and the Robinson model h ave the advantage, that they predict more precisely the skin permeatio n of highly hydrophilic and highly lipophilic chemicals compared to th e Guy and Potts model. The revised Robinson model resulted always in t he smallest residual variance.