Green Approach to Enhance Dissolution of Gliclazide: Thermoresponsive Solid Dispersion Based on Poloxamer 188/Propylene Glycol/Labrasol Ternary System

Background/Objectives: Gliclazide’s limited water solubility restricts its absorption across the gastrointestinal tract and compromises its therapeutic performance. This study developed a thermoresponsive solid dispersion based on the inverted thermoresponsive behavior of poloxamer 188 in propylene glycol. Methods: A solubility study was conducted to select components for the thermoresponsive solid dispersion. An I-optimal mixture design was used to optimize the concentrations of the thermoresponsive solid dispersion components (poloxamer 188, propylene glycol, and labrasol). FTIR and XRD were used to investigate the mechanism underlying the inverted thermoresponsive behavior. Finally, the influence of the thermoresponsive solid dispersion on gliclazide dissolution was evaluated through in vitro dissolution testing. Results: Surfactant screening identified labrasol as the optimal surfactant owing to a superior increase in gliclazide solubility compared to propylene glycol alone (2.29-fold). The optimized thermoresponsive solid dispersion (poloxamer 188, propylene glycol, and labrasol at 13.89, 21.43, and 64.68% w/w, respectively) achieved a drug solubility of 10.68 mg/g and a phase transition temperature of 36 °C. XRD and FTIR confirmed that hydrogen bonding is responsible for the system’s conversion between the solid and liquid states. Compared with raw gliclazide, the optimized formulation demonstrated an 8.4-fold increase in the initial dissolution rate and significantly improved dissolution efficiency from 21.77 ± 4.74% to 74.85 ± 2.33%. Conclusions: The present thermoresponsive solid dispersion provides a green alternative to conventional solid dispersion techniques. It avoids reliance on organic solvents, processing that demands high energy input, and additional post-processing operations.