The Correlation between Transepidermal Water Loss and Percutaneous Absorption

Abstract

The extensive procedures required to measure percutaneous absorption versus transepidermal water loss (TEWL) make it ideal to find a correlation or make a comparison between the two measurements to more easily assess skin barrier function and should aid in the understanding and development of penetration enhancers. Penetration enhancers augment penetration of a drug into or through the skin and demonstrate a synergistic relationship when used together. However, experiments investigating a quantitative and/or qualitative correlation between the two indicators (TEWL and percutaneous absorption) have resulted in controversy. In a review by Levin and Maibach in 2005, 9 studies investigating the correlation between TEWL and percutaneous absorption were examined. Of the 9 studies reviewed, a majority demonstrated a significant quantitative correlation, and a few found no quantitative correlation. At that time it was thought that the correlation between TEWL and percutaneous absorption may not hold for in vitro experimentation models, extremely lipophilic compounds, or possibly experiments performed on animal skin. Since then, several published studies have investigated the relationship between TEWL and percutaneous absorption using a very lipophilic compound, in vitro models, and animal skin. Most of these studies demonstrated a significant quantitative correlation. This paper serves as an updated review of some of the major studies investigating the correlation between TEWL and percutaneous absorption.