Percutaneous penetration paradigms: the contribution of Jonathan Hadgraft.

This paper addresses the application of physical chemistry towards understanding the processes of percutaneous penetration. Over the years, this approach has been used by the subject of this review to advance our knowledge of the skin and to interpret, model and predict dermal delivery. The basic laws of diffusion provide a framework for the comprehension of skin permeability and, as a corollary, how the barrier function can be modulated. The importance of understanding the physicochemical properties of potential skin permeants is highlighted. Rational formulation strategies for passive skin delivery are outlined. However, the overriding emphasis is that multidisciplinary approaches must be used to advance the field. This is exemplified in the work and references cited.