Abstract

Entrapment efficiency and particle size distribution are important properties affecting pharmacokinetics of liposomes upon intravenous administration. Several factors such as composition of lipids, methods of preparation etc affect these properties of liposomes. A 24 complete factorial design with replicated center point was used to quantitate the effect of four factors viz. concentration of cholesterol, phospholipid composition, concentration of stearyl arnine and shaking time on the entrapment efficiency of pentoxifylline and particle size distribution of liposomes prepared by thin film hydration method. A mathematical model containing only significant factors affecting each response was predicted using multiple linear regression and ANOVA. Stearyl amine had negative effect on the entrapment efficiency i.e. increase in concentration of stearyl amine did not cause increase in the entrapment efficiency. Particle size distribution was affected by shaking time and phospholipid composition. In addition to main factors, two way and three way interactions also had a significant effect on all the measured responses. A new formulation based on combination of factors between the experimental levels was prepared and evaluated for allresponses. Experimental values were found to be in good agreement with the predicted values.