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

Abstract

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 ≥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 ® and compounds with the same range of lipophilicity.