370 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS REFERENCES (1) Graber, M. B., Domsky, I. I., and Cinn, M. E., A TLC method for identification of germicides in personal care products, JAOCS, 46, 529-31 (1969). (2) Bravo, R., Ordenes, H., and Hern•mdez, F., Paper and plate chromatographic methods for the determination of dichlorophene and hexachlorophene when present together, J. Chromatogr., 7, 60 (1962). (3) Schwartz, H., Zur Analyse antimikrobiell wirksamer Waschmittelzusiitze, Fette, Seifen, Anstrichm., 71, 223-6 (1969). (4) K6nig, H., Trennung und Identifizierung yon Bactericiden auf der Basis yon halo- genierten Aromaten durch Diinnschicht-Chromatographie, Z. Anal. Chem., 246, 247-51 (1969). (5) Kadeskind, Valmalle, C., and Wolff, J.P., Identification et dosage des bact.•ricides dans les savons de toilette, Rev. Ft. Corps Gras, 19, 297-306 (1972). (6) Felton, H., Performance of components of a high-pressure liquid chromatography sys- tem, J. Chrornatogr. Sci., 7, 13-6 (1969).

I. Soc. Cosmet. Chem., 24, 371-384 (May 23, 1973) Physicochemical Properties and Percutaneous Absorption of Drugs* ERIC J. LIEN, Ph.D., and GEORGE L. TONG, Pharm. D.* Presented May 25, 1972, Seminar Lo, Angeles, Calif. Synopsis-With the EXTRATHERMODYNAMIC APPROACH it was found that for many series of DRUGS, PERCUTANEOUS ABSORPTION through intact skin is highly dependent upon the lipophilic character as measured by log (partition coefficient) from octanol/water, ether/water, and other suitable solvent systems. This lends support to the "barrier effect" of the stratum corneum of the epidermis against penetration by sub- stances with inadequate lip old solubility. COMPUTERIZED MULTIPLE REGRESSION ANALYSIS showed that the addition of other steric or electronic terms, such as molar refraction, Taft's polar substituent constant (½*), molecular weight, and solubility in water, significantly improved the cor- relations in some cases. The approach used would enable a cosmetic chemist to predict the relative degree of drug absorption through skin from the PHYSICOCHEMICAL CONSTANTS of series of compounds and the absorption data of a few parent molecules. INTRODUCTION Since all cosmetic preparations are intended for local application, rapid ab- sorption of the active ingredients through the skin into blood circulation is, in many cases, undesirable. However, for some medicated preparations, such as creams containing hormones or vitamins and antiperspirant products, absorp- tion into the skin is necessary for achieving the desired beneficial effect locally. In any event, it is very important for a cosmetic chemist to be able to predict the extent to which a cosmetic material or drug will be absorbed through the skin or into the skin. As a matter of fact, the need for "quantitative measure of permeability" was clearly emphasized in a 1959 seminar ( 1 ). Several useful generalizations concerning the percutaneous absorption of different types of chemicals have been well documented (2, 3). Unfortunately, *This study was supported in part by General Research Support Grant 5 SO1 RR- 05702-02 from the General Research Support Branch, National Institutes of Health. tSchool of Pharmacy, University of Southern California, University Park, Los Angeles, Calif. 90007. Inquiries should be addressed to E. J. Lien. 371