Measurement, analysis and prediction of topical UV filter bioavailability

Area of Science:

• Dermatology
• Pharmaceutics
• Physical Chemistry

Background:

• Sunscreen bioavailability is crucial for efficacy.
• Understanding topical delivery mechanisms requires objective quantification.
• Vehicle composition significantly impacts active ingredient penetration.

Purpose of the Study:

• To quantify and predict the bioavailability of three sunscreen agents (benzophenone-3, 2-ethylhexylsalicylate, 2-ethylhexyl-4-methoxycinnamate).
• To evaluate the impact of petrolatum and emulsion-based vehicles on sunscreen penetration.
• To validate a dermatopharmacokinetic method for assessing topical delivery.

Main Methods:

• Human volunteers (n=4) were treated with sunscreen formulations.
• Stratum corneum (SC) penetration was assessed using tape-stripping.
• Sunscreen agent concentrations in SC layers were quantified.
• Data were fitted to Fick's second law of diffusion.

Main Results:

• Permeability coefficients were lower for petrolatum than emulsion-based formulations.
• A robust methodology was confirmed by linear correlation between 7-min and 30-min absorption.
• Deconvolution of permeability coefficients provided insights into vehicle effects.

Conclusions:

• Vehicle formulation critically influences topical bioavailability of sunscreen agents.
• The developed dermatopharmacokinetic method reliably predicts and quantifies skin penetration.
• This approach aids in understanding bioequivalence and optimizing topical product design.