Sucrose acetate isobutyrate as an in situ forming system for sustained risperidone release

The objective of this study was to develop sustained-release sucrose acetate isobutyrate (SAIB) in situ formulations of risperidone for parenteral delivery. The formulations contained SAIB, solvent (anhydrous ethanol, ethyl lactate, or N-methyl-2-pyrrolidone), and additives such as polylactic acid (PLA). In vitro release profiles of risperidone from the SAIB formulations, which followed the Higuchii square root law, were obtained. An increase in SAIB content from 75% to 85% resulted in a reduction in the initial burst and the rate of risperidone release. The initial drug release could be increased by reducing the pH of the release medium and the release rate could be increased by an increase in drug loading. The burst release fell significantly from 20.0% to 3.5% following the inclusion of 10% (w/w) PLA in the formulations. In the case of this high viscosity depot system containing SAIB, anhydrous ethanol, PLA, and 25 mg/g risperidone, the in vivo biocompatible test results obtained support the use of SAIB as an injectable risperidone sustained-release formulation.