title: Mechanistic Evaluation of Hydration Effects on the Human Epidermal Permeation of Salicylate Esters.
abstract: We sought to understand when and how hydration enhances the percutaneous absorption of salicylate esters. Human epidermal membrane fluxes and stratum corneum solubilities of neat and diluted solutions of three esters were determined under hydrated and dehydrated conditions. Hydration doubled the human epidermal flux seen for methyl and ethyl salicylate under dehydrated conditions and increased the flux of neat glycol salicylate 10-fold. Mechanistic analyses showed that this hydration-induced enhancement arises mainly from an increase in the stratum corneum diffusivity of the three esters. Further, we showed that unlike methyl and ethyl salicylate, glycol salicylate is hygroscopic and the ∼10-fold hydration-induced flux enhancement seen with neat glycol salicylate may be due to its ability to hydrate the stratum corneum to a greater extent. The hydration-induced enhancements in in vitro epidermal flux seen here for glycol and ethyl salicylate were similar to those reported for their percutaneous absorption rates in a comparable in vivo study, whilst somewhat higher enhancement was seen for methyl salicylate in vivo. This may be explained by a physiologically induced self enhancement of neat methyl salicylate absorption in vivo which is not applicable in vitro.
authors.affiliation: Therapeutics Research Centre, School of Medicine, University of Queensland, Translational Research Institute, Brisbane, Australia.|School of Pharmacy, Helwan University, Helwan, Egypt.
authors.forename: Shereen
authors.initials: S
authors.lastname: Yousef
authors.affiliation: Therapeutics Research Centre, School of Medicine, University of Queensland, Translational Research Institute, Brisbane, Australia.
authors.forename: Yousuf
authors.initials: Y
authors.lastname: Mohammed
authors.affiliation: Therapeutics Research Centre, School of Medicine, University of Queensland, Translational Research Institute, Brisbane, Australia.
authors.forename: Sarika
authors.initials: S
authors.lastname: Namjoshi
authors.affiliation: Therapeutics Research Centre, School of Medicine, University of Queensland, Translational Research Institute, Brisbane, Australia.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Grice
authors.affiliation: School of Pharmacy, Helwan University, Helwan, Egypt.
authors.forename: Wedad
authors.initials: W
authors.lastname: Sakran
authors.affiliation: Therapeutics Research Centre, School of Medicine, University of Queensland, Translational Research Institute, Brisbane, Australia. m.roberts@uq.edu.au.|School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, Australia. m.roberts@uq.edu.au.|Therapeutics Research Centre, The University of Queensland School of Medicine-Translational Research Institute, 37 Kent St, Woolloongabba, Brisbane, QLD, 4102, Australia. m.roberts@uq.edu.au.
authors.forename: Michael
authors.initials: M
authors.lastname: Roberts
mesh_terms: D000279:Administration, Cutaneous; D015194:Diffusion Chambers, Culture; D004817:Epidermis / Q000378:metabolism*; D004952:Esters; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008954:Models, Biological; D010539:Permeability; D012459:Salicylates / Q000737:chemistry / Q000493:pharmacokinetics*; D012869:Skin Absorption; D012995:Solubility; D012996:Solutions; D014867:Water / Q000378:metabolism*
chemical_list: D004952:Esters; D012459:Salicylates; D012996:Solutions; D014867:Water
keywords: diffusivity; hydration; in vitro human skin permeation; in vivo comparison; topical salicylate esters