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OBJECTIVE To establish an accelerated method that has good correlations with in vivo release data for quality control purposes of thymopentin-loaded poly (dl-lactide-co-glycolide) (PLGA) microspheres.METHODS In vivo thymopentin release from the microspheres was studied in Sprague-Dawley rats at first.Then the accelerated release of these depot formulations was studied in two typical release media.After that,the effects of organic solvents types,ethanol concentrations,surfactant concentrations and heating temperature were investigated and optimized in formulation 13K.Finally,the modified accelerated release method was validated in the three formulations and their correlations with in vivo release were calculated.RESULTS 20% hydro-alcoholic solutions (V/V) and 0.06% Tween80 (W/V) were selected and fixed in the accelerated release method.A gradient heating program,consisting of three stages and each stage with a different temperature (0~1 h at 40 ℃,1~6 h at 45 ℃ and 6~30 h at 50 ℃),was introduced into the accelerated release method and the correlation constant R2 of 8,13 and 28 K formulation was 0.9783,0.9886 and 0.9780,respectively.CONCLUSION By optimizing the conditions as alcohol concentration and temperature gradients,this accelerated method can be used in quality control of thymopentin-loaded PLGA microspheres.