LAUSR

Abstract Characterizing the release mechanism of microspheres in vitro and in vivo can establish a more convincing in vitro–in vivo correlation. In this paper, long-acting donepezil microspheres were prepared using the emulsion solvent evaporation technique. Subsequently, the release kinetics of the drug, as well as the mechanistic indicators of the release, such as glass transition temperature, mass loss, water uptake, and microsphere swelling, were directly measured and analyzed in vitro and in vivo. Drug release from microspheres was significantly accelerated in vivo compared with incubation in vitro. The mass loss data indicated that the microsphere exhibits diffusion and erosion via jointly controlled release both in vivo and in vitro, but the control of erosion on release is enhanced in vivo. The microspheres absorb water more quickly in vivo compared with incubation in vitro. The study showed that there are some unknown substances or biochemical reactions in the in vivo environment that cause the microspheres to absorb water quickly and accelerate the degradation of the polymer.