Investigation of Transfollicular Caffeine Penetration Using Microdialysis on Ex Vivo Porcine Ear Skin

The study conducted in December 2020 developed an ex vivo method to measure the penetration of caffeine through porcine ear skin, focusing on the role of hair follicles. Using microdialysis and selective follicular closure, it was found that caffeine penetrated rapidly in areas with open follicles, with the highest median concentration reached at 35 minutes, while closed follicles showed significantly reduced penetration. After 22 hours, caffeine levels equalized across all skin areas. The study confirmed that hair follicles are a significant pathway for the permeation of topically applied substances and that the mechanical impact of varnish used for follicular closure did not affect the results. The probability of the microdialysis membrane hitting a hair follicle was 4%, and the study's findings are consistent with previous research, suggesting that combining microdialysis with other techniques could provide a more complete understanding of penetration pathways and kinetics.