Percutaneous absorption of sunscreens in vitro: Interspecies comparison, skin models and reproducibility aspects

Appropriate evaluation of sunscreens is required to provide better knowledg e of their safety and efficacy. One of the most important elements of this evaluation is the assessment of percutaneous absorption. In vitro methods a re largely used for such assessments, and the accuracy of the measurements generated with these methods depends on the use of a proper methodology. Th is study was designed to evaluate an in vitro protocol for investigating th e percutaneous absorption of two sunscreens under standardized experimental conditions. Octyl methoxycinnamate and benzophenone 4 were each incorporat ed in a typical oil-in-water emulsion and tested separately. Salicylic acid was tested as a reference compound. In vitro percutaneous absorption was e valuated using two species, the pig and human, and two models, full-thickne ss and split-thickness skin. The reproducibility of study results was evalu ated by comparing the data generated by two industrial laboratories, L'Orea l and Hoffmann-La Roche. The correlation of quantitative data between pig s kin and human skin was very good, and the split-thickness skin model seemed to be more appropriate for measuring the absorption of sunscreens. Results obtained for salicylic acid demonstrated the relevance of the protocol in terms of prediction of in vivo percutaneous absorption. Finally, the compar ison of pig skin data between the two laboratories demonstrated a good corr elation and underlined the need for a standardized in vitro procedure. Copy right (C) 2000 S, Karger AG, Basel.