IN VITRO INTERACTION OF VEHICLES 257 140 120 - 100 - 81)- 20- I I I I 6 8 10 12 14 16 Hydrocarbon chain length Figure 2. Effect of chain length of the hydrocarbons on the calculated steady-state flux at saturation (J*) of caffeine through female dorsal hairless mouse skin. REFERENCES (1) B. Idson, Vehicle effects in percutaneous absorption, Drug. Metab. Rev., 14, 207-222 (1983). (2) M. S. Roberts and R. A. Anderson, The percutaneous absorption ofphenolic compounds: The effect of vehicle on the penetration of phenol, J. Pharm. Pharmacol., 27, 599-605 (1975). (3) H. Schaefer, G. Stuttgen, A. Zesch, W. Schalla, and J. Gazith, Quantitative determination of percutaneous absorption of radiolabeled drugs in vitro and in vivo by human skin, Curr. Probl. Dermatol., 7, 80-94 (1978). (4) R. L. Bronaugh and R. F. Stewart, Method for in vitro percutaneous absorption studies. IV. The flow-through diffusion cell, J. Pharm. Sci., 74, 64-67 (1985). (5) R. L. Bronaugh, R. F. Stewart, E. R. Congdon, and A. L. Giles Jr., Method for in vitro percutaneous absorption studies. I. comparison with in vivo results, Toxicol. Appl. Pharmacol., 62, 474-480 (1982). (6) W. J. Addicks, N. D. Weiner, R. L. Curl, and G. L. Flynn, "Drug Delivery From Topical For- mulations: Theoretical Prediction and Experimental Assessment," in Topical Drug Delivery Formula- tions, D. W. Osborne and A. H. Amann, Eds. (Marcel Dekker, New York, 1990), p. 239. (7) K. Knutson, R. O. Potts, D. B. Guzek, G. M. Golden, J. E. McKie, W. J. Lambert, and W. I. Higuchi, Macro- and molecular physical-chemical considerations in understanding drug transport in the stratum corneum, J. Control. Rel., 2, 67-87 (1985). (8) T. Kai, V. Mak, R. O. Potts, and R. H. Guy, Mechanism of skin penetration enhancement: Effect of n-alkanols on the permeability barrier. Presented at the 15th International Symposium on Con- trolled Release of Bioactive Materials, Abstract 124, Basel, Switzerland, 1988. (9) J. R. Evans and C. Hughes, In vitro methodology for investigating quantitative relationships between skin permeation and compound structure, J. Pharm. Pharmacol., 38, 68P (1986).

258 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (10) C. W. Barrett, J. W. Hadgraft, G. A. Caron, and I. Sarkany, The effect of particle size and vehicle on the percutaneous absorption of fluocinolone acetonide, Brit. J. Dermatol., 77, 576-578 (1965). (11) M. J. Busse, P. Hunt, K. A. Lees, P. N. D. Maggs, and T. M. McCarthy, Release of betamethasone derivatives from ointments--In vivo and in vitro studies, Brit. J. Dermatol., 81, (Suppl. 4), 103-111 (1969). (12) J. S. Turi, D. Danielson, and J. W. Woltersom, Effect of polyoxypropylene 15 stearyl ether and propylene glycol on percutaneous penetration rate of diflorasone diacetate, J. Pharm. Sci., 68, 275- 280 (1979). (13) N. V. Sheth, D. J. Freeman, W. I. Higuchi, and S. L. Spruance, The influence ofazone, propylene glycol and polyethylene glycol on in vitro skin penetration of trifluorothymidine, Int. J. Pharm., 28, 201-209 (1986). (14) B. Mollgaard and A. Hoelgaard, Permeation of estradiol through the skin--Effect of vehicles, Int. J. Pharm., 15, 185-197 (1983). (15) A. J. Aguiar and M. A. Weiner, Percutaneous absorption studies of chloramphenicol solutions, J. Pharm. Sci., 58, 210-215 (1969). (16) H. Komatsu and M. Suzuki, Percutaneous absorption of butylparaben through guinea pig skin in vitro, J. Pharm. $ci., 68, 596-598 (1979). (17) J. N. Twist and J. L. Zatz, The effect of solvents on solute penetration through fuzzy rat skin in vitro, J. $oc. Cosmet. Chem., 40, 231-242 (1989). (18) J. Ostrenga, C. Steinmetz, B. Poulsen, and S. Yett, Significance of vehicle composition. II. Predic- tion of optimal vehicle composition, J. Pharm. Sci., 60, 1180-1183 (1971). (19) B. Mollgaard and A. Hoelgaard, Vehicle effect on topical drug delivery. II. Concurrent skin transport of drugs and vehicle components, Acta Pharm. Suec., 20, 443-450 (1983).