Author(s): Abhishek Gandhi, Swati Guttikar and Priti Trivedi*
A simple, sensitive and specific liquid chromatography–tandem mass spectrometry method was developed and validated for quantification of exemestane.Exemestane is an irreversible, steroidal aromatase inactivator and it is indicated for adjuvant treatment of postmenopausal women with estrogen-receptor positive early breast cancer.The analyte and internal standard (IS)(exemestane-D2) were extracted by liquid-liquid extraction withethyl acetate: n-Hexane (80:20v/v) solvent mixture. The chromatographic separation was performed on a reverse phase Kinetex 2.6µ C18, 50 × 4.6 mm column with a mobile phase of 0.01% (v/v) acetic acid in water andacetonitrilein gradient composition.Exemestane was quantitated in positive ionization by multiple-reaction-monitoring with a mass spectrometer. The mass transitions m/z 297.4 → 121.2 and m/z 299.4 → 123.2 were used to measure exemestane and exemestane-D2 respectively.The assay exhibited a linear dynamic range of 0.100–40.0 ng/ml for exemestane in human plasma. The lower limit of quantitation achieved was 0.100ng/mL for exemestanewith a relative standard deviation of less than 20%. Acceptable precision and accuracies were obtained for concentrations over the standard curve ranges.A run time of 8.0 minutes for each sample made it possible to analyze more than 100 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic and bioequivalence studies.