PERCUTANEOUS ABSORPTION OF DRUGS 373 (cm/hr), where C was the molar concentration measured or required to cause a standard biological response, and Kp was the permeability constant. For the detailed procedure of the absorption study the original references should be consulted. The absorption data and the physicochemical constants used in the regression analysis are assembled in Tables I-VI. The general Table II In Vitro Permeability of Nonelectrolytes through Rabbit Whole Skin and Rabbit Dermis Log P Whole Skin Dermis Compound Log MW Log MRa a (Octanol/ Log Kp (cm/hr) Log K• (cm/hr) Water) Obsd b Calcd c Diff Obsd b Calcd a Diff Ethyl iodide 2.19 1.39 2.00 Methanol 1.51 0.91 --0.66 Ethanol 1.6'6 1.11 --0.16 * Thiourea 1.88 1.14 -- 1.70 Glycerol 1.96 1.29 --2.56 Urea 1.78 1.32 --2.79 Glucose 2.26 1.58 --3.29 --2.26 --2.26 0.00 ......... --2.59 --2.70 0.11 --0.93 --0.97 0.04 --2.57 --2.63 0.06 --1.07 --1.05 --0.02 --3.76 --3.42 --0.34 --1.17 --1.18 0.01 --3.63 --3.82 0.19 --1.26 --1.23 --0.03 --3.84 --3.75 --0.09 -- 1.14 -- 1.12 --0.02 --4.27 --4.35 0.08 --1.37 --1.40 0.03 Calculated from the molecular refractivities given in ref. 11. From ref. 12. Calculated from eq 9. Calculated from eq 12. Experimentally determined values from ref. 13. Calculated value. Table III In Vitro Permeability of Aliphatic Alcohols through Human Epidermis Compound Log Ko • Log P Log K. Log Kp (cm/hr) (Octanol/Water) Obsd * Calcd a Dif[ Water ...... --0.52 --3.00 ...... Methanol --2.10 --0.66 c --0.22 --3.00 --3.24 0.24 Ethanol --1.52 --0.16 • --0.22 --3.00 --2.97 --0.03 n-Propanol --0.77 0.34 • 0.30 --2.85 --2.70 --0.15 n-Butanol --0.30 0.84 • 0.40 --2.60 --2.43 --0.17 n-Pentanol 0.70 1.34 t 0.70 --2.22 --2.16 --0.06 n-Hexanol 1.06 1.84 t 1.00 --1.89 --1.88 --0.01 n-Heptanol 1.79 2.34 t 1.48 --1.49 --1.61 0.12 n-Octanol 2.34 2.84 • 1.70 --1.28 --1.34 0.06 Ko = olive oil/water partition coefficient from ref. 14. K. ----- stratum eorneum/water partition eoefiieient from ref. 14. From ref. 14. Calculated from eq 14. Experimentally determined value from ref. 13. Calculated value.

374 JOUBNAL OF THE SOCIETY OF COSMETIC CHEMISTS