Determination of Sunitinib and Its Plasma Protein Binding Rate in Human Plasma by HPLC

OBJECTIVE To establish HPLC method combined with equilibrium dialysis or ultrafiltration for the determination of sunitinib and its plasma protein binding rate in human plasma. METHODS The HPLC analysis of sunitinib was achieved on Waters XBridge^TM C₁₈ (4.6 mm×250 mm, 5 µm) with a mobile phase composing of methanol-0.02 mol·L^-1 sodium dihydrogen phosphate (70:30) at a flow rate of 1.0 mL·min^-1, and the detection wavelength was 310 nm. RESULTS The calibration curve for plasma sunitinib was linear in the range of 0.057 5-34.5 μg·mL^-1, and the lower limit of quantification was 0.057 5 μg·mL^-1. At three different concentrations, the plasma protein binding rates were (84.1±2.1)%, (81.0±1.8)%, (80.6±1.6)% by equilibrium dialysis, respectively, and were (80.8±1.7)%, (84.2±2.0)%, (82.6±2.2)% accordingly by ultrafiltration. Both results were quite similar. CONCLUSION The HPLC method is simple, rapid, sensitive, and can effectively meet the needs of further analysis. And sunitinib has high plasma protein binding rate, which is independent of its plasma concentration.