THE RELATIVE EFFECT OF AZONE(R) AND TRANSCUTOL(R) ON PERMEANT DIFFUSIVITY AND SOLUBILITY IN HUMAN STRATUM-CORNEUM

Purpose. The purpose of this work was to analyse the mechanism of the enhancement of percutaneous penetration demonstrated by the known enha ncers Atone(R) and Transcutol(R). Methods. Enhancer induced changes in the diffusivity and solubility of a model permeant (4-cyanophenol) in human stratum corneum were monitored (in-vitro) using Attenuated tota l reflectance Fourier transform infra-red (ATR-FTIR) spectroscopy and compared to the gross effects of the enhancers on flux as measured usi ng simple Franz-type diffusion cells. Results. It has been shown by bo th the well-established Franz diffusion cell technique and the use of ATR-FTIR spectroscopy that the enhancers studied both increase the flu x of cyanophenol across human skin in-vitro by a factor of approximate ly two. Furthermore, it has been demonstrated by ATR-FTIR that these e nhancers are likely to exert their effects by different mechanisms. It is probable that Atone reduces the diffusional resistance of the stra tum corneum and that Transcutol increases the solubility of the penetr ant in this barrier. Conclusions. There is increasing interest in the apparently synergistic nature in which certain enhancers appear to wor k. The exact nature of these multiplicative and/or additive effects is not known although there are numerous suggestions in the current lite rature. The application of ATR-FTIR spectroscopy to such enhancing sys tems will allow the mechanisms of the observed enhancements to be prob ed in greater depth.