STABILITAS DAN TRANSPOR MELEWATI MEMBRAN IMPREGNASI ISOPROPIL MIRISTAT SEDIAAN MIKROEMULSI ASKORBIL PALMITAT

Ascorbyl palmitate is a derivative of ascorbic acid which has a more lipophilic than ascorbic acid. Ascorbic acid as a hydrophilic compound, in topical formulation has low penetration through the skin. Ascorbyl palmitate has better penetration through the skin than that of ascorbic acid. Problem of ascorbic acid and its derivatives have a low stability in topical formulation. Microemulsion may increase stability of drugs and have better penetration through the skin. The objective of this research was to evaluate stability and penetration of ascorbyl palmitate in microemulsion through the isopropyl miristate impregnated membrane. Ascorbyl palmitate microemulsion was made by low energy process. Verification of analytical method was done. Physical stability of microemulsion was examined for viscosity, phase separation and homogeneity. Stress testing was also performed to the drug for hydrolisis (0.1 N HCl, water and 0.1 N NaOH) and oxidation (3% H2O2). A degradation of ascorbyl palmitate in a microemulsion that stored at temperature of 25°C and of 40°C was examined by using HPLC method. The release and transport of ascorbyl palmitate in a microemulsion was carried out using Franz cell diffusion type with methanol and phosphate buffer (pH 6.5) (50%:50%) as receptor media. Ascorbyl palmitate microemulsion changed in colour, viscosity and pH values during storage at temperature of 25°C and of 40°C. The stability of microemulsion, ascorbyl palmitate underwent degradation by route of hydrolysis at first and then followed by oxidation. Based on t1/2 and t90, chemical stability of ascorbyl palmitate increased in microemulsion formulation, better than in phosphate buffer (pH 5.4). Ascorbyl palmitate in microemulsion could diffuse through impregnated membrane, the diffusion coefficient and permeability had values which were lower than in non impregnated membrane