Preclinical and clinical characterization of the cutaneous bioavailability of the hydrophilic phase of a water-in-oil emulsion

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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.

Patients and 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.

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