A mathematical approach to predicting the percutaneous absorption enhancing effect of sodium lauryl sulphate

A study has been made of the effect of sodium lauryl sulphate (SLS) at several concentrations from 0.24 to 5% (w/w) on skin permeability. Seven model drugs were selected for this study on the basis of their lipophilicity as represented by their log P-oct values (from -0.95 to 4.2). Skin pre-treatment with aqueous solutions of SLS does not increase the permeability coefficient of the most lipophilic compounds (log P-oct greater than or equal to 3). For the other compounds assayed the increase in the permeability coefficients depends on the concentration of SLS used in the skin pre-treatment, and on the lipophilicity of the compounds tested. The correlation between the inverse of SLS efficacy as an enhancer (1/ER) and the lipophilicity (log P-oct) of the model permeants was established via a hyperbolic equation. This model makes it possible to predict the percutaneous absorption enhancing effect of SLS, expected for a compound of specific lipophilicity, according to the concentration used in skin pre-treatment. An excellent accuracy (r(2) > 0.94) for the linear relationship between the experimental (n = 15) and theoretical (ER) values predicted by the equation was obtained. The model proposed was also useful for experimental data obtained previously using Azone(R) and compounds with the same range of lipophilicity. (C) 2003 Elsevier B.V. All rights reserved.