Percutaneous absorption of organic solvents. III. On the penetration rates of hydrophobic solvents through the excised rat skin.

The penetration rates of 10 hydrophobic solvents through the excised abdominal rat skin were quantitatively determined by using the in vitro method reported previously. The hydrophobic solvents studied were benzene, toluene, ethylbenzene, o-xylene, styrene, n-pentane, 2-methylpentane, n-hexane, n-heptane and n-octane. There was a great diversity in the ability of the hydrophobic solvents to penetrate through the excised rat skin, but a good correlation between the penetration rates and the solubility of the solvents in water was observed. The log-log plot of the penetration rate versus the solubility in water showed a linear relationship ; log y=1.41 log x-0.297, r =0.981, where y is the penetration rate (n moles/min/cm2 of skin) and x is the solubility of the solvent in water (mM at 25•Ž). The solubility in water was found to be a reliable index of the skin penetration rate for the hydrophobic solvents.