Drug Release Kinetics from Nondegradable Hydrophobic Polymers Can Be Modulated and Predicted by the Glass Transition Temperature.

Controlling drug release kinetics within a desired therapeutic window is the central task when designing polymeric drug delivery systems. Complex polymer chemistries have often been explored to control water penetration, polymer degradation rate, or the mesh network size of delivery systems. Here, a simple parameter for controlling the release rate and duration of nondegradable hydrophobic polymers is discovered. A systematic study involving 59 polymers and multiple drugs demonstrates that the glass transition temperature, Tg , is a critical factor that dictates drug release kinetics from nondegradable hydrophobic polymers. Drug release rate exhibits a unique and simple linear correlation of (T - Tg )0.5 despite variability of polymer structure and type. An empirical model established based on the special correlation can accurately simulate and predict drug release kinetics from polymers saving substantial time typically required to test long-acting drug delivery systems.