Abstract This investigation aimed to develop polycaprolactone (PCL) microspheres, which provide better control of valsartan release. Central composite experimental design (2‐factor, 3‐level) was used to study the effect of two independent variables, namely drug amount (X1) and organic phase volume (X2), on encapsulation efficiency (Y1) and particle size (Y2). The drug‐containing microspheres were prepared by a single emulsion solvent evaporation method and characterized by various techniques including high performance liquid chromatography, thermal analysis, X‐ray diffraction analysis, scanning electron microscopy, and particle size analysis. The optimum conditions found by the quadratic models were yielded microspheres with an encapsulation efficiency of about 79 and a particle size of 51 μm. The optimal formulation improved drug release in simulated gastric fluid for the first 2 h, while it provided a sustained release, in phosphate buffered saline (pH 6.8). The formulations prepared with a lower organic phase volume (4 ml) have reduced the burst effect and therefore provided better control of valsartan release. Mathematical modeling studies showed that the encapsulated drug release was governed by Fickian‐diffusion mechanism.
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