Preparation of ropivacaine hydrochloride multivesicular liposomes and release in vitro

Aim ：To prepare ropivacaine hydrochloride multivesicular liposomes，and to study the physicochemical properties and drug release behavior in vitro. Methods ：Ropivacaine hydrochloride multivesicular liposomes were prepared by the multiple emulsion method.Single factor experiments were utilized to study the factors which affect the encapsulation efficiency of multivesicular liposomes.The formulation and pharmaceutical process were optimized by Box-Behnken experimental design，with the factors of encapsulation efficiency as the criteria.Three batches of the optimized multivesicular liposomes were prepared， and the encapsulation efficiency and in vitro release behavior were studied. Results ：The particle size of the optimized multivesicular liposomes was uniform and 85% of them were well distributed in the range of 7-30 μm.The encapsulation efficiency was up to 90% when the ratios of lipid to drug，phospholipids to cholesterol and the amount of triolein was 1.328∶1(w/w)，1.5∶1(w/w) and 6 mmol/L，respectively.The release profile in vitro fitted to a first-order kinetics with the period of release up to 48 h in PBS buffer under 37 °C. Conclusion ：Ropivacaine hydrochloride multivesicular liposomes showed high encapsulation efficiency and significant sustained-release feature.