44 JOURNAL OF COSMETIC SCIENCE 12• 10 t I 84 i T IPM solution Emulsion ß Stratum Comeurn '• a!pha-TAc in viable skin [] alpha-T in viable skin []Total amount permeated Figure 5. Permeation profile at six hours. Values are percentage of applied dose, mean _+ SEM (n = 4). 10- '- c• 4 •' 2 0 3' -•_•:.• 1 IPM solution Emulsion ß Stratum Corneum [] alpha-TAc in viable skin []alpha-T in viable skin Total amount permeated Figure 6. Permeation profile at 12 hours. Values are percentage of applied dose, mean + SEM (n = 4). solution, the amount at 24 hours was significantly higher than that at two and six hours. The total amount permeated in this case probably reaches a plateau at six hours and does not significantly increase after that. Total ot-TAc and ot-T permeated in viable skin was significantly higher in the ot-TAc emulsion at 24 hours and six hours than at two hours. The emulsion had higher amounts of metabolite at 12 hours, although at the end of the study period (24 hours), there was no significant difference between the two formula- tions in terms of the amount of metabolite ot-T formed in viable skin. Figure 8 shows the total ot-TAc and ot-T in viable skin. The figure depicts the gradual increase in deposition of both compounds into viable skin with time, as shown by its linear profile. The extent of metabolism (EX, %) has been calculated in the viable skin and total skin

PERMEATION AND METABOLISM OF ot-T and ot-TAc 45 25- 20q 15• 0 IPM solution Emulsion ß Stratum Corneum [] alpha-TAc in viable skin [] alpha-T in viable skin [] Total amount permeated Figure 7. Permeation profile at 24 hours. Values are percentage of applied dose, mean + SEM (n = 4). • aipha-TAc IPM solution ß alpha-TAc emulsion 8 •6 •4 2 0 t , 0 10 20 30 Time (hrs) Figure 8. Total c•-TAc and c•-T permeated into viable skin. Values are percentage of applied dose, mean + SEM(n = 4). as shown in equations 1 and 2. Equation 1 refers to the extent of metabolism in viable skin only, whereas equation 2 represents the extent of metabolism in the viable skin and stratum corneum (represented as total skin in the equation). T A(vs) EX(vs) AT ATAc x 100 (1) (vs) + (vs) T A(vs) EX(TOTALSKiN ) AT AT^c ATAc X 100 (2) (vs) + (vs) + • •(•c) A is the amount of tx-T or tx-TAc as microgram of drug. The subscript (vs) refers to the viable skin, whereas the subscript (sc) refers to stratum corneum. The superscript refers to either tx-T or tx-TAc. For example, the numerator refers to the amount of tx-T in micrograms present in viable skin. In this study EX(vov^•SKiN ) is always less than