Simultaneous Determination of Imatinib and its Active Metabolite by UPLC-MS/MS in Rat Plasma and its Application to a Pharmacokinetic Study

A rapid and sensitive ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was developed for the determination of concentration of imatinib and its active metabolite N-desmethyl imatinib in rat plasma. The imatinib and its active metabolite and the internal standard (carbamazepine) were separated on an Acquity UPLC BEH C18 chromatography column (2.1 mm x 50 mm, 1.7 mu m) using gradient elution with a mobile phase of acetonitrile and 0.1% formic acid in water at a flow rate of 0.4 mL/min. The detection was performed on a triple quadrupole tandem mass spectrometer by multiple reaction monitoring (MRM) mode to monitor the precursor-to-product ion transitions of m/z 494.2 -> 394.2 for imatinib, m/z 480.2 -> 394.2 for N-desmethyl imatinib and m/z 237.1 -> 194.2 for carbamazepine (IS) using a positive electrospray ionization interface. The method was validated for 1.0-2000 ng/mL for imatinib and 0.5-200 ng/mL for N-desmethyl imatinib using 100 mu L of plasma sample. Total time for each chromatograph was 3.0 min. The intra- and inter-day precision and accuracy of the quality control samples at low, medium, and high concentration levels exhibited relative standard deviations (RSD) < 9.7% and the accuracy values ranged from -11.1% to 9.3%. The method was successfully applied to a pharmacokinetic study of imatinib and N-desmethyl imatinib in rats after oral administration of imatinib.