The comparative histology of porcine and guinea pig skin with respect to iontophoretic drug delivery.

The anatomy of pig skin, neonatal pig skin, and hairless guinea pig skin was investigated with respect to iontophoretic drug transport. Fixed sections of skin were stained with hematoxylin and eosin, and the morphology of the skin appendages was examined. Quantitative measurements of the hair follicle density, diameter and lumen area were obtained, and the effective surface areas available for low resistance iontophoretic transport were calculated. The clustering and density of the follicles of neonatal porcine skin and hairless guinea pig skin suggest that linear mass transport may dominate iontophoretic flux. In contrast, the morphology and density of the hair follicles of porcine skin suggests that a radial mass transport mechanism may dominate iontophoretic transdermal drug delivery.