title: LC-MS-MS determination of exemestane in human plasma with heated nebulizer interface following solid-phase extraction in the 96 well plate format.
abstract: A sensitive, specific and rapid analytical method for the quantitation of exemestane (EXE) in human plasma has been developed. EXE, 6-methylen-androsta-1,4-diene-3,17-dione, is an orally active irreversible steroidal aromatase inhibitor used for the therapy of metastatic postmenopausal breast cancer, with estrogen-dependent pathological conditions. The method involves extraction of EXE from human plasma by solid phase extraction using C2 endcapped sorbent in the 96 well plate format (50 mg/2 ml). After conditioning of the sorbent with 1 ml of acetonitrile (x2) the plates were rinsed with 1 ml of water (x2). The prepared samples (0.5 ml plasma, spiked with [13C3] EXE as internal standard (IS) and diluted with 0.5 ml water) were loaded and drawn through the plate with a minimum of vacuum. The plates were then washed with 1 ml acetonitrile:water (10:90) followed by a drying step for 30 min at full vacuum. Elution was by 0.15 ml of 0.1% trifluoracetic acid in acetonitrile (x2) under a minimum of vacuum. Aliquots of 80 microl were finally injected into the LC-MS-MS system. A Zorbax SB C8 column (4.6 x 150 mm, 5 microm) was used to perform the chromatographic separation; the mobile phase was 100% acetonitrile. MS detection used the heated nebulizer interface, with multiple reaction monitoring (MRM) (297-->121 m/z for EXE and 300-->123 m/z for IS) operated in positive ion mode. A weighed linear regression analysis (weighing factor 1/x2) was used to calculate EXE concentration in standard and unknown samples. The method was fully validated in the concentration range 0.05-25 ng ml(-1).
authors.affiliation: Pharmacia and Upjohn, Drug Metabolism Research, Milan, Italy.
authors.forename: V
authors.initials: V
authors.lastname: Cenacchi
authors.forename: S
authors.initials: S
authors.lastname: Barattè
authors.forename: P
authors.initials: P
authors.lastname: Cicioni
authors.forename: E
authors.initials: E
authors.lastname: Frigerio
authors.forename: J
authors.initials: J
authors.lastname: Long
authors.forename: C
authors.initials: C
authors.lastname: James
mesh_terms: D000730:Androstadienes / Q000097:blood*; D000970:Antineoplastic Agents / Q000097:blood*; D002853:Chromatography, Liquid / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D013058:Mass Spectrometry / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results
chemical_list: D000730:Androstadienes; D000970:Antineoplastic Agents; C056516:exemestane