Pore change during degradation of octreotide acetate-loaded PLGA microspheres: The effect of polymer blends

The purpose of this study was to solve the plateau phase (the stage in which the drug in the microsphere undergoes a slow release or almost no release after initial release) problem by understanding the effect of polymer blends on the internal pore changes of the microspheres. This study used PLGA 5050 4H (F-1), PLGA 5050 1A: PLGA 5050 4H = 3:7 (F-2) and PLGA 7525 1A: PLGA 5050 4H = 3:7 (F-3) as a carrier, respectively. Microspheres (MS) were obtained by O/W emulsion solvent evaporation technique and characterized by scanning electron microscopy (SEM), particle size, drug loading, fluorescence characteristics, and in vitro and in vivo release. Accelerated tests in vitro showed that the size and number of core pores significantly affected drug release in the first and second phases. After intramuscular administration, F-2 and F-3 showed effective blood concentration levels and their bioavailability was higher than that of the RLD (Sandostatin Lar). In general, our data indicate that pore formation is unevenly distributed throughout PLGA MS prepared using polymer blends, and the use of polymer blends is instructive for the development of sustained smooth release microspheres. Therefore, the octreotide MS described in this study has a good clinical application potential for the treatment of acromegaly.