A novel tetrandrine-loaded chitosan microsphere: characterization and in vivo evaluation

In this study, novel tetrandrine-loaded chitosan microspheres were prepared by the emulsion cross-linking method. The systems were then characterized for physicochemical properties and in vitro drug release. In addition, the pharmacokinetics and tissue distribution of microspheres were further verified in animal models. Particle-size distribution indicated that the size of microspheres was within the range of 7–15 μm, with a median diameter of 12.4 μm. The drug loading and entrapment efficiency of the formulation were 34.6%±12.5% and 87.3%±9.7% (mean ± SD), respectively. In vitro release showed a typical sustained and long-term drug release behavior. The Higuchi equation was the model that fit best with release data. Maintaining a relatively constant plasma concentration in the long-term drug treatment is an outstanding pharmacokinetic advantage of tetrandrine microspheres in vivo. Moreover, compared with tetrandrine solution, tetrandrine microspheres produced a lower drug concentration in the heart, liver, and kidneys. This indicated that the microspheres used in this study were preferable for targeting lung tissue versus other tissues. No damage to the tissues of the lung was found in histopathological examination.