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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