The effects of depilatory agents as penetration enhancers on human stratum corneum structures.

The depilatory cream thioglycolate has been shown to be an effective enhancer for transdermal drug delivery. However the mechanism remains unknown. In addition, it may also increase the risk of permeation of exogenous toxic agents across skin in depilatory cream users. The aim of this study was to characterize its effect on the transepidermal route and the associated structural alterations. Fresh human skin was treated with a depilatory cream for 10 minutes and then permeated with fluorescent model drugs. The penetration of model drugs was then imaged and quantified. The structural alternations of stratum corneum were assessed by multi-photon imaging, histology, Nile red staining, and electron microscopy. Our results show that penetration of both hydrophilic and hydrophobic model drugs across stratum corneum was enhanced. Disruption of cellular integrity and focal detachment of superficial corneocytes was observed in multi-photon imaging. In addition, nile red staining showed disorganized lipid distribution. Finally, ultrastructural analysis revealed disruption of intracellular keratin matrix, protein cell envelope, and regular lamellar intercellular lipid packing. Because intracellular and intercellular structures were altered, our results suggest that depilatory agents enhance transepidermal drug delivery by reducing resistance in both transcellular and intercellular routes of stratum corneum.