32765 Regional variation in percutaneous absorption in in vitro human models: A systematic review

Abstract

Percutaneous absorption is of importance given its role in topical medicaments, transdermal drug systems, and dermatotoxicology. Many factors influence percutaneous absorption, including anatomical location. Hence, this study summarizes the existing data on regional variation in percutaneous absorption in in vitro human models. PubMed, Embase, and Web of Science were explored, and literature containing quantitative data on regional differences in percutaneous absorption in humans in vitro, was collected. Eight relevant articles were identified, which together, explored 15 anatomic regions. Four studies compared percutaneous absorption between scalp and abdominal skin, and all concluded that the former was more permeable. Within those 4 studies, 10 penetrants of varying physical/chemical properties were tested, suggesting that anatomical location has a greater effect on percutaneous absorption than the penetrants’ properties. Additionally, torso was less absorptive than scrotum in both studies in which these sites were compared. In conclusion, the scrotum and scalp appear to be highly vulnerable to percutaneous absorption when compared with other regions such as the abdomen. This is thought to be largely due to the high hair follicle density in these areas, allowing for greater penetration through the appendageal pathway. However, there is a paucity of conclusive data regarding the absorptivity of other anatomical locations. Experimentation testing and ranking the vulnerability of different anatomical locations is of vital importance given its relevance in decontamination and transdermal drug delivery protocols, and understanding the mechanisms and degree of these variances should aid our pharmacologic/toxicologic judgments.