Species differences in percutaneous absorption of nicorandil

The species difference in skin permeability, Kp, of nicorandil was determined by using excised skin samples from hairless mouse, hairless rat, guinea-pig, dog, pig, and human. The Kp value of nicorandil in hairless mice was the greatest among the six species, and those in pigs and humans were in good agreement. To clarify the reasons for the species difference, various skin characteristics in each species were measured. It was suggested that the difference of skin surface lipids in each species affected the partitioning of nicorandil from vehicle to stratum corneum, and that such a difference would be a main factor for the species difference in nicorandil permeability. Since pig and human skins had similar surface lipids, barrier thickness, and morphological aspects, percutaneous absorption studies using excised pig skin samples would be useful for the estimation of in vitro human skin permeation behavior.