Stability and release of topical tranexamic acid liposome formulations

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 4degrees, 30degrees and 45degreesC 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 37degreesC for 24 h. The release rates of TA from all liposome formulations were similar to 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.