ABSTRACT
A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantification of gefitinib in dried blood spots (DBSs). Gefitinib was extracted with methanol from DBS of 3â¯mm in diameter and detected using a triple quadrupole mass spectrometer. The method was validated by evaluating its precision, accuracy, selectivity, carryover, matrix effect, recovery, and stability. For clinical validation, paired finger-prick DBS and plasma concentrations were compared for 10 patients with non-small cell lung cancer (NSCLC) taking gefitinib. The calibration linear range was 37.5-2400â¯ng/mL (coefficient of determination [R2]â¯=â¯0.99), encompassing the therapeutic concentrations of gefitinib. The accuracy and precision were within 15% of the quality control (QC) concentrations of 80, 200, and 2000â¯ng/mL. The lower limit of quantification was determined to be 40â¯ng/mL. Gefitinib was stable in DBSs for up to 5â¯months at room temperature and -20⯰C, and at 40⯰C for 24â¯h. A good correlation was observed between the gefitinib levels measured by the DBS method and plasma concentrations (R2â¯=â¯0.99). This method provides a simple, fast, and accurate approach to the quantitative analysis of gefitinib in finger-prick DBSs. The method would be useful for minimally invasive evaluation of the clinical gefitinib blood concentration.