A liquid chromatography with tandem mass spectrometry（LC-MS/MS） method has been developed and validated for the measurement of sunitinib in rabbit plasma. After protein precipitation with acetonitrile, samples were analyzed on a Zorbax Extend-C18 column（150 mm×4.6 mm, 5μm）. The mobile phase consisted of a mixture of acetonitrile and deionized water（containing 0.05% formic acid） at a ratio of 27：73（v/v）, and the flow rate was set at 0.8 mL /min. The column temperature was maintained at 30 oC. The LC eluate was detected by an electrospray ionization（ESI） source operated in the positive ion mode, and quantification was conducted using MRM of the transitions m/z 399.24→283.01 and m/z 415.19→178.00 for sunitinib and internal standard（IS, diltiazem hydrochloride）, respectively. The calibration curve was linear in the range of 2–600 ng/m L. The lower limit of quantification was 2 ng/mL. The method also exhibited satisfactory results in terms of sensitivity, specificity, accuracy（with relative error ranging from –4.0% to 1.1%）, precision（with intra- and inter-day relative standard deviations ranging from 2.8% to 9.5%）, matrix effect, recovery as well as stability. Taken together, our newly developed method was reliable to monitor sunitinib concentrations in rabbit plasma.
Drug-loaded microspheres have been caused much attention in embotherapy in recent years. In thlS StUdy, poiyvlnyi alcohol/acrylic acid microspheres were prepared by inverse suspension polymerization method. Sunitinih malate （SU） was used as a model drug and loaded on microspheres through ion-exchange mechanism. We investigated the characterization of blank microspheres （B-Ms） and sunitinib-loaded microspheres （SU-Ms） in vitro, including morphology, size distribution, equilibrium water content （EWC）, elasticity, drug loading and drug release. The result showed that both B-Ms and SU-Ms were spherical with smooth surface. The particle size of B-Ms and SU-Ms were both suitable for embolization. Compared with that of B-Ms, the EWC of SU-Ms was decreased and the rigidity of SU-Ms was increased. Drug loading and entrapment efficiency of microspheres were mainly affected by the concentration of sunitinib solution than by the size of microspheres. SU-Ms exhibited a sustained release in phosphate buffer solution （PBS）. Thus, the SU-Ms may have potential application for arterial embolization.
