382 JOURNAL OF COSMETIC SCIENCE 120 lOO o• 80 ._• c. •o .•_ ,_• • 40 • 20 o 7:2:1 (5%TA,+) 7:2:1 (10%TA,+) 7:2:1 (5%TA,-) 7:2:1 (10%TA,-) i i i i 0 30 60 90 120 Time (Days) a) at 4+ 1 øC 12] 721 (5%TA.+) 721 (10%TA.+) 721(5%TA-) •m•••• 1(10%TA") b) at 30+1 øC o 3] fid fid 120 Trne(Dsys) 120 [ • 7:2:1 (5% TA,+) 7:2:1 (10%TA,+) 100 7:2:1 (5%TA,-) 7:2:1 (10%TA,-) 80 60 40 20 0 • , C) at 45+1 øC o 30 60 90 120 Time (Days) Figure 1. Comparison of the percentages of TA remaining in liposomes when kept at (a) 4 +_ 1 ø (b), 30 + 1% (c) 45 + IøC for 0, 14, 30, 60, and 90 days. Symbols are the mean values of six determinations.

TRANEXAMIC ACID LIPOSOMES 383 Table IV Leakage Rate Constants (k) and Predicted Shelf Lives (t9o) of the Entrapped TA in Liposomes •'b k (day -1) t9o (days) Formulations 4øC 30øC 45øC 4øC 30øC 45øC 7:2:1 (5% TA,+) 0.0030 0.0046 0.0055 35.1 22.8 19.0 7:2:1 (10% TA,+) 0.0030 0.0039 0.0046 35.1 26.8 22.8 7:2:1 (5% TA,-) 0.0023 0.0032 0.0039 45.6 32.6 26.8 7:2:1 (10% TA,-) 0.0016 0.0023 0.0030 65.1 45.6 35.1 Experimental data represent the mean value of six determinations. The k and t9o values were estimated using the first-order equation. Table V Degradation Rate Constants (k in day -•) of Total TA in Liposomes, and in the Pellets of Liposomes •'b k of total TA in liposome k of total TA in pellet Formulations 4øC 30øC 45øC 4øC 30øC 45øC 7:2:1 (5% TA,+) 0.0002 0.0009 0.0016 0.0030 0.0055 0.0069 7:2:1 (10% TA,+) 0.0005 0.0016 0.0014 0.0028 0.0053 0.0058 7:2:1 (5% TA,-) 0.0002 0.0007 0.0009 0.0062 0.0062 0.0023 7:2:1 (10% TA,-) 0.0014 0.0012 0.0012 0.0023 0.0018 0.0035 Experimental data represent the mean value of six determinations. The k and t9o values were estimated using the first-order equation. Table VI Release Rate Constants (k) of TA and the Total Amount of TA Released From Liposomes and Solution During 24 Hours at 37øC •'b Formulation Release rate constant (%/h •/2) Total release of TA (%) 7:2:1 (5% TA,+) 6.12 + 0.06 28.05 + 1.45 7:2:1 (10% TA,+) 8.13 + 0.05 36.20 + 1.24 7:2:1 (5% TA,-) 6.29 + 0.07 29.22 + 1.71 7:2:1 (10% TA,-) 8.27 + 0.04 37.93 -+ 1.04 5% TA solution 18.89 + 0.21 81.69 + 5.03 10% TA solution 19.77 + 0.20 87.32 + 4.90 Experimental data represent the mean value of six determinations. The values were estimated using the Higuchi model equation. were observed in all liposome formulations following storage at 4 ø, 30 ø, and 45øC for 90 days, indicating the high physical stability of these liposome systems (Table II). These formulations may have stable electrically double layers of the multilamellar vesicles, within the pH range of 6.9 to 7.9. Following storage at 30 ø and 45øC for 90 days, the positively charged liposomes with the entrapped TA demonstrated a more marked increase in the turbidity of the supermatant, compared to the negatively charged liposomes with the entrapped TA (Table II). Thus, charges appeared to affect the physical stability of the liposomes. In all stability studies, better correlations (r 2 = 0.91) were obtained when the observed