Preparation and Physicochemical Evaluation of Injectable Sustained-Release Risperidone by Lipid Liquid Crystal Vehicle

Introduction: Risperidone is a highly effective medicine in patients with mental disorders. Since maintaining blood concentrations of risperidone within the therapeutic index is pivotal during treatment, these patients should receive medication daily and continuously. Method: In this study, an optimal lipid liquid crystal was designed according to the maximum release for 60 days based on different ratios of phosphatidylcholine (PC) to sorbitan monooleate (PC:SMO), tween 80 (w/w%), and tocopherol acetate (w/w%) using Design Expert software with the Central Composite Design (CCD) method. Release evaluations were conducted in vitro to compare the effects of lipid liquid crystal and Risperdal CONSTA®. The structure evaluation was also tested using polarized electron microscopy and in vitro assessment via cell culture. Results: The optimal formulation was selected based on the maximum release (100%) of the drug obtained within 2 months with a PC: SMO ratio of 58.6%, tween 0.82% (w/w), and tocopherol acetate 3.6% (w/w). A hexagonal mesophase with a dihedral structure was observed in the liquid crystal structure. No toxicity was observed in the cell culture test. Conclusion: The comparison of the results of in vitro studies of the liquid crystal formulation containing risperidone and the commercial formulation, Risperdal CONSTA®, showed that the liquid crystal system provides better and more uniform drug release for 60 days. Therefore, it can increase patient compliance and ease the problems of oral administration