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Abstract

A diffusion model for the skin penetration of drug in the finite-dose system was developed considering the skin to be composed of two layers, the outermost layer (stratum corneum) and the lower layer (viable epidermis and dermis). Based on this skin model, the Laplace transforms of the equations for the drug amounts in the receptor, the vehicle, and the skin were derived. The penetration profiles of 6-mercaptopurine (6-MP) through the intact and stripped guinea pig skin were obtained from in vitro diffusion experiments. The computer fitting of those profiles to the Laplace-transformed equations by a nonlinear least-squares program based on a fast inverse Laplace transform algorithm [MULTI-(FILT)] gave parameters such as diffusion coefficients of 6-MP and thicknesses of both layers. The mean transit time (MTT) for each diffusion process was defined based on statistical moment concept and calculated using the obtained parameters. Under the present condition, the process to move from the vehicle to the stratum corneum is demonstrated to have the longest mean time in overall processes of 6-MP penetration.

Permeation Pathway of Macromolecules and Nanospheres through Skin

“…23) To clarify the differences of skin permeation profiles between hairless rat skin and LSE-high, the partition parameter and diffusion parameter were compared. Table 4 shows the partition and diffusion parameters, which were calculated from curve-fitting the time course of the cumulative amount of FL and FD-4 permeating hairless rat skin and LSE-high.…”

Solute-Vehicle-Skin Interactions in Percutaneous Absorption: The Principles and the People

“…Others, as summarised in our work [8], have also argued that the skin barrier has an overall polarity so that maximum solubility and penetration will occur when the solute has a similar polarity. In yet another interpretation, the non-appendageal skin barrier can be seen as a series of barriers (lipid-corneocyte-lipid [9]; stratum corneum-viable epidermis-unstirred water/dermis [10,11,12]). Each of the above models predicts a convex or parabolic relationship between the epidermal flux for a series of different solutes from saturated solutions in a particular vehicle and the log P of the solute.…”