Injectable Controlled-Release Systems

Abstract

Injectable controlled-release systems occupy a strategic position in pharmaceutical drug delivery: they require no surgical implantation, they can be administered in an outpatient setting, and they achieve the sustained local or systemic drug concentrations that oral or intravenous administration cannot maintain without multiple daily doses. The range of injectable controlled-release technologies has expanded substantially, from the clinically established PLGA microsphere platform that has been in use for leuprolide and risperidone depots since the 1980s and 1990s respectively, to self-assembling peptide-polymer hybrids that form structured drug release matrices in situ with millisecond gelation kinetics. Comparative evidence across system types remains fragmented by indication, with no cross-system framework that addresses all four major clinical deployment contexts simultaneously. This study presents the Injectable Controlled-Release System Assessment Framework (ICRSAF), evaluating five injectable controlled-release system types -- PLGA microsphere injectables (PLGA-MS), in situ forming gel and depot systems (ISF-GD), lipid-based injectable suspensions (LIS), hydrogel nanocomposite injectables (HNI), and peptide-polymer hybrid self-assembling systems (PPH-SA) -- across four clinical contexts: oncology, chronic pain management, psychiatric and neurological care, and metabolic disease management. Performance was scored using the Release System Effectiveness Score (RSES), a weighted composite of release profile control (0.30), injection site tolerance (0.20), clinical efficacy (0.20), manufacturing reproducibility (0.15), and patient acceptance (0.15). PLGA microsphere systems achieved the highest RSES (0.882) through the best manufacturing reproducibility (0.900) and strong release profile control (0.900), supported by four decades of commercial production experience. In situ forming gel systems ranked second (0.877) with the best injection site tolerance (0.900). Hydrogel nanocomposites (0.872) achieved the study's best release profile control (0.920). Lipid suspensions (0.866) and peptide-polymer hybrids (0.863) both showed strong context-specific performance with distinct clinical advantages.