j. Cosmet. Sci., 53, 375-386 (November/December 2002) Stability and release of topical tranexamic acid liposome formulations A. MANOSROI, K. PODJANASOONTHON, and J. MANOSROI, Pharmaceutical-Cosmetic Raw Materials and Natural Products Research and Development Center, Institute •br Science and Technology Research and Development, Faculty of Pharmacy, Chiang Mai University, Chiang Mai 50200, Thailand. Accepted •br publication April 29, 2002. Synopsis Tranexamic acid (TA) has been claimed to have whitening effects. The effects of TA contents (5% and 10%) and charges on the stability and release of TA entrapped in hydrogenated soya phosphatidylcholine/ cholesterol/charged lipid {dicetyl phosphate (-) or stearylamine (+)} liposomes at molar ratios of 7:2:1(-) and 7:2:1 (+) were investigated. The TA contents were determined spectrophotometrically at 415 nm, following derivatization with 2,4,6-trinitrobenzosulfonic acid. Stability and leakage of TA from liposomes were characterized at 4 ø, 30 ø and 45øC for 90 days. The leakage rates of TA in negative liposomes were lower than those in positive liposomes. The TA in all liposome formulations was relatively stable, as 90% of total drug remained after up to two months. The release of TA from liposomes was examined using vertical Franz diffusion cells at 37øC for 24 h. The release rates of TA from all liposome formulations were - 3 times lower than those from solutions. Charges appeared to affect the physical stability, leakage, and shelf life of TA in liposomes, whereas TA concentrations seemed to affect the release of TA. The 7:2:1 (10% TA,-) liposome was the best formulation, due to its small size, low leakage, high stability, and prolonged and sustained release profile. INTRODUCTION Liposomes are excellent novel formulations as drug and cosmetic carriers, owing to their biodegradability, biocompatibility, low toxicity, and ability to entrap lipophilic and hydrophilic drugs (1,2). In addition, liposomes may enhance the penetration of drugs into the skin with a slow release and have a moisturizing effect (3). The tissue distri- bution and release of drugs from liposomes may be affected by particle size, composition of the lipid, and surface charges of the liposomes (4). In scintigraphic studies, liposomes carrying radionuclides within the aqueous space have potential diagnostic imaging applications (2). Gamma-emitting radionuclides, such as 99mTc, •In and 67Ga have Address all correspondence to A. Manosroi. 375

376 JOURNAL OF COSMETIC SCIENCE been encapsulated in liposomes for imaging agents (5-7). Some clinical trials for tumor imaging using labeled liposomes have already been initiated (7-9). Tranexamic acid (TA) is a hydrophilic drug used as an antifibrinolytic agent (10-15). It is a trans-4-aminomethyl cyclohexane carboxylic acid (CsH•5NO2, mw 157.21) (16). It has been claimed that TA has anti-inflammatory (16) and whitening effects for topical use (17). The current commercially available preparations of TA are tablets and injec- tions (18). We have previously developed liposome formulations for TA from various lipid compositions, containing neutral or positively or negatively charged lipids, which may potentially reduce the irritation and allergy caused by TA and improve the mois- turizing effect (19). It was found that the charged liposome composed of hydrogenated soya phosphatidylcholine/cholesterol/stearylamine (+) or dicetyl phosphate (-) at a molar ratio of 7:2:1 for TA demonstrated 13-16% of drug entrapment. Thus, these liposome formulations were selected for further stability and release studies. It is expected that the developed liposome formulations can be applied for the future development of TA, not only as a sustained release preparation but for topical whitening cosmetics as well. The present study reports the characterization of stability and release of TA from various multilamellar liposome formulations, prepared by a chloroform film method with soni- cation. The release rates of TA from liposomes were compared with those of free TA from solutions (5% and 10% in deionized water). Various factors (TA content and charges of liposomes) that may affect the stability and release properties of TA are discussed. EXPERIMENTAL MATERIALS TA was obtained commercially from Asahi Chemical Industry Co., Ltd. (Japan). Hy- drogenated soya phosphatidylcholine (Emulmetik 90 ©) (HSC) was kindly donated by JJ-Degussa (T) Ltd., Bangkok. Cholesterol (CHL), dicetyl phosphate (DCP), stearyl- amine (SA), 2,4,6-trinitrobenzosulfonic acid, and boric acid were purchased from Sigma Chemical Company (St. Louis, MO). Triton-X 100 was obtained from BDH Ltd. (Poole, England). Chloroform and potassium dihydrogen orthophosphate were of analytical reagent grade. PREPARATION OF LIPOSOMES Liposome dispersion samples were prepared by a chloroform film method with sonica- tion as previously described (19). The lipids used were neutral (HSC and CHL) and charged lipids (SA for positively charged lipids and DCP for negatively charged lipids), with a total lipid concentration of 25 mg/ml. Liposome formulations composed of HSC/CHL/SA = 7:2:1(+) and HSC/CHL/DCP = 7:2:1(-) at molar ratios, with the entrapped TA (5% and 10% solutions in DI water), were prepared. For each lot, an amount of 60 ml of each liposome dispersion sample was prepared. The liposome dispersion samples were kept at 4 ø + løC and protected from light prior to use.