Flow-through versus static in vitro percutaneous penetration at 50 years: Possible relevance for bioequivalence

Abstract

Objective: Compare the relevance of flow-through versus static diffusion cells data as relates to bioequivalence. Methods: Search was conducted on PubMed and Google Scholar. Keywords utilized: static cells, flow-through cells, percutaneous permeation, percutaneous absorption, dermal absorption, and types of permeation. Results: Fifteen articles were identified with no consistent significant differences between flow-through and static diffusion cells identified; any differences could exist for two main reasons. (1) Sampling time differences and (2) physical chemistry (lipophilic vs hydrophilic) of the penetrant examined. Conclusion: Even though there was no consistent significant difference observed, labs have generally adapted to the method they regularly use, which is usually stated in their respective articles. Well-designed multicentered prospective comparative experiments should clarify potential advantages and disadvantages for each. For flow-through systems, the flow rate that most approximates to comparable in vivo data for animals and humans may be preferable.