ABSTRACT
INTRODUCTION The prediction of skin absorption remains a major goal in a number of fields including topical drug discovery, the cosmetic and cosmeceutical industries, and risk assessment for dermal exposure to toxic substances. There are obvious advantages in developing reliable predictive techniques that can eliminate or reduce the need for extensive and expensive experimental studies. Since the early recognition that the lipid-rich stratum corneum (SC) formed the major barrier to skin penetration by exogenous substances (1) and that physicochemical properties could determine the rate of penetration (2), much work has been done on identifying the relevant physicochemical properties. The outcome of such work has usually been in the form of algorithms known as quantitative structure-activity relationships (QSARs) or quantitative structurepermeability relationships (QSPRs) to predict skin transport. Recent reviews on QSAR/QSPR use in regulatory risk assessment (3) and general skin permeability (4) have highlighted the limitations that remain with the technique.
