266 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table I Amount of Percutaneous Absorption of LAEO Four Hours After Application Intravital Fecal and Expiratory LAEO Amount Urinary Excretion Excretion Percent Absorbed Lauryl Alcohol 17.7 + 1.9 1.2 + 0.2 27.2 + 1.0 LAEO-1 22.9 + 1.9 17.1 + 0.7 16.1 + 1.8 -- LAEO-2.6 15.6 _+ 0.6 40.8 _+ 3.2 4.8 _+ 0.5 -- LAEO-6.4 10.4 _+ 0.3 16.4 _+ 2.4 1.0 _+ 0.2 -- LAEO-10 2.1 _+ 0.1 2.5 + 0.4 0.3 + 0.02 46.1 + 0.9 56.1 _ 4.2 61.2 + 2.8 27.8 + 2.8 4.9 _ 0.4 Applied dose: 1.38 •mole/25 •1 ethanol (1.0 •Ci). Dorsal skin of hairless mouse: 2.9 cm 2. The values are expressed as percent of the applied quantity. LAEO. Table II shows the amount of the percutaneous absorption, the amount remaining in the applied skin, and the sum of these or recovery rate in this experimental system. Table II Recovery Rate in This Experimental System Percent Retained Sample Name Percent Absorbed by the Excised Skin Percent Recovery Lauryl Alcohol 46.1 _+ 0.9 52.9 + 2.0 98.5 -+ 1.5 LAEO-1 56.1 + 4.2 43.5 -+ 6.0 99.3 -+ 2.2 -- LAEO-2.6 61.2 + 2.8 40.5 _+ 2.8 101.3 + 2.6 -- LAEO-6.4 27.8 + 2.8 71.8 + 2.0 99.7 + 1.4 -- LAEO-10 4.9 -+ 0.4 95.7 + 0.9 100.6 _+ 1.2 Applied dose: 1.38/xmole/25/xl ethanol (1.0/xCi). Dorsal skin of hairless mouse: 2.9 cm 2. The values are expressed as percent of the applied quantity. It can be seen from the recovery pattern that the method used allows reliable and reproducible measurement of percutaneous absorption. The data clearly show that LAEO-1 and LAEO-2.6 penetrate the skin readily, while LAEO-10 is barely absorbed. MEASUREMENT OF PERCUTANEOUS ABSORPTION RATE OF LAEO In order to obtain the rate of percutaneous absorption of LAEO, changes in absorption with time for the various LAEO were determined (Figure 2). Each exhibited linearity after a slight time lag. The rates obtained from the slopes of these lines are shown in Table III. Lauryl alcohol was the fastest followed by LAEO-2.6 and LAEO-1. LAEO-10 had a slower rate by one order of magnitude. MEASUREMENT OF PERCUTANEOUS ABSORPTION RATE FROM EXPIRATORY EXCRETION We also followed the percutaneous absorption rate from expiratory excretion by measuring •4CO2 in the expired air over a period of time after percutaneous absorption of •4C-LAEO. The time rate of change of the percent •4CO2 expired for each LAEO is

PERCUTANEOUS ABSORPTION OF SURFACTANTS 267 50 q0 • 30 • 20 z lO LAURYL ALCOHOL TiME (HOURS) 50 q0 3O 2O 10 LAEO-1 ej i i i 2 TiME (HOURS) 50 q0 3O 2O 10 LAEO-•.6 LAEO-10 I [ I 0 i 2 3 0 8 12 16 TIME (HOURS) T[ME (HOURS) Figure 2. Percutaneous absorption curves of LAEOs. Applied dose: 1.38/amole/25 tzl ethanol (1.0 tzCi). Dorsal skin of hairless mouse: 2.9 cm 2. Each point is the mean of 3 animals. Table III Rates of Percutaneous Absorption of LAEOs LAEO Rate of Percutaneous Absorption (/amole/cm 2 ß hrs) Lauryl Alcohol 12.2 x 10 -2 LAEO-I_._ 9.77 x 10 -2 LAEO-2.__6 9.78 x 10 -2 LAEO-10 0.75 x 10 -2 Applied dose: 1.38 tzmole/25 tzl ethanol. Dorsal skin of hairless mouse: 29 cm 2.