In Vitro Testing of Sunscreens for Dermal Absorption: Method Comparison and Rank Order Correlation with In Vivo...

Area of Science:

• Dermal toxicology
• Cosmetic science
• Pharmacokinetics

Background:

• Evaluating sunscreen UV filter dermal absorption is crucial for safety assessments.
• In vitro permeation tests (IVPT) are needed to predict in vivo skin absorption.
• Existing IVPT methods require validation for bio-predictability.

Purpose of the Study:

• To compare two IVPT methods for evaluating dermal absorption of UV filters.
• To correlate in vitro absorption data with in vivo absorption data.
• To identify the most bio-predictable IVPT method for sunscreen UV filters.

Main Methods:

• Compared single finite dose vs. infinite dose application in IVPT.
• Compared heat-separated human epidermis vs. dermatomed skin models.
• Evaluated dermal absorption of six UV filters in commercial sunscreens using IVPT and in vivo studies.

Main Results:

• Both in vivo and in vitro studies showed UV filter absorption after single application.
• The IVPT method using a single finite dose and heat-separated human epidermis correlated well with in vivo clinical data.
• Rank orders for cumulative in vitro skin permeation and in vivo AUC were comparable for several UV filters (oxybenzone, homosalate, octisalate, octinoxate).

Conclusions:

• The validated IVPT method using a single finite dose and heat-separated human epidermis provides bio-predictable results for sunscreen UV filter dermal absorption.
• This method can be used to rank UV filters based on their absorption potential.
• Further optimization of IVPT parameters may improve predictions for UV filters with low skin permeation.