title: Preclinical and clinical characterization of the cutaneous bioavailability of the hydrophilic phase of a water-in-oil emulsion.
abstract: BACKGROUND
  Interactions between the stratum corneum and individual phases of an emulsion system depend on various factors, but primarily on the outer continuous phase of the system. While there is plenty of data on the lipophilic phase, only very little data exists on the actual penetration of the hydrophilic phase of water-in-oil emulsions into the stratum corneum.
  
  
  METHODS
  Against this background, two comparable water-in-oil emulsions were preclinically and clinically investigated on healthy as well as on artificially damaged skin with regard to interactions of the hydrophilic phase. In preclinical studies, following epicutaneous application on ex vivo skin, the distribution of the hydrophilic phase was quantified using fluorescence tests and analyzed according to anatomic layers. Additionally, a randomized, controlled, investigator-blinded study investigated the effects of the preparations on the barrier function of healthy and artificially damaged skin over time.
  
  
  RESULTS
  The results clearly show that water substitution using a water-in-oil emulsion can only partially be attained by the addition of hygroscopic substances (e. g. urea). These effects may primarily be explained by the occlusive properties of the lipophilic phase.
  
  
  CONCLUSIONS
  This, the use of water-in-oil emulsions may in particular be recommended for chronic barrier impairment, as long-lasting effects are not to be expected in acutely damaged skin.
authors.affiliation: Department of Dermatology and Venereology, Martin-Luther -University Halle-Wittenberg, Halle (Saale), Germany.|Institute of Applied Dermatopharmacy, Martin-Luther -University -Halle-Wittenberg, Halle (Saale), Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Wohlrab
authors.affiliation: Department of Dermatology, -Venereology and Allergology, Charité University Medicine Berlin, Berlin, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Richter
authors.affiliation: Department of Dermatology and Venereology, Martin-Luther -University Halle-Wittenberg, Halle (Saale), Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Stauder
mesh_terms: D000279:Administration, Cutaneous; D001682:Biological Availability; D004655:Emulsions / Q000493:pharmacokinetics*; D006801:Humans; D012867:Skin; D012871:Skin Diseases / Q000188:drug therapy*; D014867:Water
chemical_list: D004655:Emulsions; D014867:Water