Solvent-exchange-based in situ forming implants: advances and challenges as long-lasting formulations

Solvent-based ISFIs represent an important strategy for achieving long-lasting effects with a single administration independent of patient compliance. Their main impact has been in mental and substance use disorders, but they are also useful for local effects. To date, one formulation has been approved for periodontitis, though applications in ocular diseases and osteoarthritis are anticipated. A key formulation challenge is to reduce the initial drug release. Most marketed formulations are based on PLGA/PLA dissolved in NMP. Recently, DMSO and PEGylated-based-ISFIs have been approved, which generally provide better drug release control and will likely lead to the development of new formulations.