DETERMINATION OF CAPECITABINE-AN ANTICANCER DRUG IN DRIED BLOOD SPOT BY LC-ESI-MS/MS Original Article

Objective: Capecitabine (Cape), the first oral prodrug which belongs to the group of fluoro pyrimidines is the most frequently prescribed anticancer drug for the treatment of metastatic breast and colorectal cancers. The article describes a selective and robust method for determination of Cape in dried blood spots (DBS) by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Methods: Cape fortified DBS was punched and extracted with ethyl acetate using capecitabine-d11 as the internal standard (IS). Chromatographic separation of Cape and IS from endogenous matrix was performed on Phenomenex Gemini C18 (150 × 4.6 mm, 5µm) column under isocratic condition using acetonitrile: 2 mmol ammonium formate (pH 3.0, adjusted with 0.1 % formic acid) (80:20, v/v) as the mobile phase. Detection and quantification were carried on a triple quadrupole mass spectrometer, using electro spray ionization technique in the positive ionization mode. Results: The method was established over a concentration range of 10-10000 ng/ml. Accuracy, precision, selectivity, recovery, matrix effect and stability of the analyte were also estimated and the results were within the acceptance criteria. Further, precise results were obtained using an optimum spot volume of 10 µl with good spot homogeneity. Blood samples with hematocrit values varying from 24 % to 45 % gave acceptable results with good accuracy and precision. Conclusion: The efficiency of dried blood spot sample preparation, short analysis time and high selectivity permits estimation of Cape in a small blood volume. The validation results suggest that the method is precise, accurate, and reproducible and can be useful in therapeutic drug monitoring of Cape.