Dermal absorption and pharmacokinetics of isopropanol in the male and female F-344 rat.

Isopropanol (IPA), as a 70% aqueous solution, was applied under occluded conditions to the shaved backs of male and female Fischer F-344 rats for a period of 4 hr. Maximum analyzed blood concentrations of IPA were attained at 4 hr and decreased steadily following removal of the test material. Blood concentrations were below the limit of quantification at 8 hr. Acetone (ACE) blood levels rose steadily during the 4-hr exposures and continued to rise following removal of the test material, reaching peak analyzed levels at 4.5 hr (male) and 5 hr (females). ACE blood concentrations were below the limit of quantification at 24 hr. Basic pharmacokinetic parameters were similar for male and female rats with mean, first-order elimination half-lives for IPA and ACE of 0.8 to 0.9 hr and 2.1 to 2.2 hr, respectively. Following iv administration of [ 14 C]IPA, 50–55% of the dose was eliminated as 14 CO 2 with lesser amounts recovered as expired volatiles or in urine. Total recoveries following iv administration were 83% for both males and females. Following a 4-hr dermal exposure to [ 14 C]IPA (70% aqueous solution), 84–86% of the dose was recovered from the application site. Dermal absorption rates were calculated by two independent methods. The values obtained were 0.78 ± 0.03 and 0.85 ± 0.04 mg/cm 2 /hr for males and 0.77 ± 0.13 and 0.78 ± 0.16 mg/cm 2 /hr for females. Calculated permeability coefficients of 1.37 to 1.50 x 10 -3 cm/hr for males and 1.35 to 1.37 x 10 -3 cm/hr for females indicate that in the rat, IPA is rapidly absorbed dermally when applied under occluded conditions.