Comparison of percutaneous penetration in vitro using clofibric acid esters and amides as novel enhancers in two species: mouse and guinea pig

A series of clofibric acid esters and amides has been assessed as dermal penetration enhancers towards hydrocortisone-21-acetate, a model drug. In vitro percutaneous absorption experiments on three skin sources (athymic nude mouse, hairless mouse, and hairless guinea pig) showed several compounds to be effective penetration enhancers, the octyl amide providing an approximately 20-fold increase in 24 h diffusion cell receptor drug concentration and 5.7 fold in total steroid skin retention in nude mouse. Azone produced significantly higher (p <0.05) permeation rates than the octyl amide enhancer, but there was a smaller increase in 24 h receptor concentrations, and Azone steroid skin concentrations were significantly less (p < 0.05) than those for the amide. There was no significant difference (p < 0.05) between enhancement in hairless and athymic nude mouse, however, hairless guinea pig skin showed decreased enhancer effectiveness.