Mechanistic model for transdermal transport including iontophoresis

A mechanistic model is presented to describe the transdermal transfer of drugs. In the model, flux is divided into the contributions through the lipid matrix and through aqueous pores. During iontophoresis, only flux through aqueous pores is enhanced because the relative permittivity of the lipid matrix is too low to allow the existence of free ions which could work as current carriers. The transfer through the lipid matrix is assumed to take place in three steps: (i) partition at the skin/reservoir interface; (ii) diffusion through the lipid matrix; (iii) desorption at the stratum corneum/epidermis interface. Simulations to the present model agree with experimental results in the literature.