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Thus it is conceivable that the fast initial drug release during in vitro dissolution tests takes place by drug release of the outer noncrystalline layers of the particles. The following sustained drug release can be assigned to the predisolone release of the inner crystalline particle layers.

Background: There is a basic necessity to understand the mechanisms of the protective effects of emulsions. This would promote the development of protective cosmetics and therefore improve the prevention and treatment of occupational skin diseases. However, for such studies, no reliable skin model is available. Objective: An in vitro skin model test was developed to evaluate the protective mechanism of cosmetic ingredients. Methods: The efficacy of three products was assessed by an in vivo test (Repetitive Occlusive Irritation Test) and then 3-dimensional skin model tests were carried out. Results: In vivo test results demonstrate that the best protection against sodium dodecyl sulphate is offered by a multiple emulsion. In the case of a skin model test, sodium dodecyl sulphate led to cell damage, an increase in pro-inflammatory markers and some barrier lipids. The multiple emulsion increased the content of skin lipids, without inducing irritation or cell death. Conclusion: Skin models react similarly to sodium dodecyl sulphate compared to human skin and therefore they are suitable to study barrier repair after sodium dodecyl sulphate damage. It is likely that the superior protective effect of the multiple emulsion in vivo is based on the increased amount of skin barrier lipids.

Skin models support the understanding of the interaction of irritants and pre-work creams. Because they are in vitro models, there are no limitations regarding the selection of irritants, which offers numerous opportunities to test a broad range of workplace irritants.