Enhancement of in vitro skin permeation of verapamil

A number of compounds including aliphatic esters, alkanols and amides were investigated for their ability to enhance the in vitro permeation rate of verapamil across hairless mouse skin. While several of them did enhance the permeation rate, the best results were obtained with the lauric acid derivatives. On analysis of the permeation rate data it was found that while most of the compounds increased the solubility of verapamil in skin and hence its partition coefficient from the delivery system, the lauric acid derivatives also increased its diffusivity in skin. Permeation of verapamil from delivery systems containing these lauric derivatives was further investigated through delipidized and stripped skin. It was found that most of these derivatives enhanced the permeation of verapamil across both whole and delipidized skin, indicating that in addition to their action on the skin lipids, they must also have some effect on the proteins in the stratum corneum.