SPE UPLC MS/MS assay for determination of letrozole in human plasma and its application to bioequivalence study in healthy postmenopausal Indian women
A rapid and sensitive ultra performance liquid chromatography tandem mass spectrometry (UPLC MS/MS) method is described for determination of letrozole in human plasma. Following solid phase extraction (SPE) of letrozole and letrozole d4 on Orochem DVB LP cartridges, chromatography was performed on Acquity UPLC BEH C18 (50 mmx2.1 mm, 1.7 um) column using methanol 0.1% formic acid in water (85:15, v/v) as the mobile phase. Detection was carried out on a triple quadrupole mass spectrometer with an electrospray source, operated under positive ionization mode. Quantitation of letrozole and letrozole d4 was done using multiple reaction monitoring (MRM) following the transitions at m/z 286.2 217.0 and m/z 290.2 221.0, respectively. The calibration plots were linear through the concentration range of 0.10 100 ng/mL (r2>=0.9990) using 100 uL human plasma. The extraction recovery of letrozole ranged from 94.3% to 96.2% and the intra batch and inter batch precision was =5.2% The method was successfully applied to a bioequivalence study of letrozole after oral administration of 2.5 mg tablet formulation to 16 healthy postmenopausal Indian women. The assay reproducibility was also established through incurred sample reanalysis (ISR) of 74 subject samples.
Journal of pharmaceutical analysis