Garg Uttam, Scott David, Frazee Clint, Kearns Gregory, Neville Kathleen
Departments of *Pathology and Laboratory Medicine, and †Pediatrics; and Divisions of ‡Pediatric Pharmacology and Therapeutic Innovation, and §Hematology/Oncology, University of Missouri-Kansas City School of Medicine, the Children's Mercy Hospital.
Ther Drug Monit. 2015 Jun;37(3):325-30. doi: 10.1097/FTD.0000000000000145.
Hydroxyurea is used in the treatment of various malignancies and sickle cell disease. There are limited studies on the pharmacokinetics of hydroxyurea, particularly in pediatric patients. An accurate, precise, and sensitive method is needed to support such studies and to monitor therapeutic adherence. We describe a novel gas chromatography-mass spectrometry (GC-MS) method for the determination of hydroxyurea concentration in plasma using stable labeled hydroxyurea C N2 as an internal standard.
The method involved an organic extraction followed by the preparation of trimethylsilyl (TMS) derivatives of hydroxyurea for GC-MS selected ion-monitoring analysis. The following mass-to-charge (m/z) ratio ions for silated hydroxyurea and hydroxyurea C N2 were monitored: hydroxyurea-quantitative ion 277, qualifier ions 292 and 249; hydroxyurea C N2-quantitative ion 280, qualifier ion 295. This method was evaluated for reportable range, accuracy, within-run and between-run imprecisions, and limits of quantification.
The reportable range for the method was 0.1-100 mcg/mL. All results were accurate within an allowable error of 15%. Within-run and between-run imprecisions were <15%. Samples were stable for at least 4 hours at room temperature, 2 months at -20°C, and 6 months at -70°C, and after 3 freeze/thaw cycles. Extraction efficiency for 1-, 5-, 10-, and 50-mcg/mL samples averaged 2.2%, 1.8%, 1.6%, and 1.4%, respectively.
The isotope-dilution GC-MS method for analysis of hydroxyurea described here is accurate, sensitive, precise, and robust. Its characteristics make the method suitable for supporting pharmacokinetic studies and/or clinical therapeutic monitoring.
羟基脲用于治疗多种恶性肿瘤和镰状细胞病。关于羟基脲的药代动力学研究有限，尤其是在儿科患者中。需要一种准确、精密且灵敏的方法来支持此类研究并监测治疗依从性。我们描述了一种新颖的气相色谱 - 质谱联用（GC - MS）方法，该方法使用稳定同位素标记的羟基脲(^{13}C_1N_2)作为内标来测定血浆中羟基脲的浓度。
该方法包括有机萃取，随后制备羟基脲的三甲基硅烷基（TMS）衍生物用于GC - MS选择离子监测分析。监测硅烷化羟基脲和羟基脲(^{13}C_1N_2)的以下质荷比（m/z）离子：羟基脲 - 定量离子277，定性离子292和249；羟基脲(^{13}C_1N_2) - 定量离子280，定性离子295。对该方法的报告范围、准确性、批内和批间不精密度以及定量限进行了评估。
该方法的报告范围为0.1 - 100 mcg/mL。所有结果在15%的允许误差范围内准确。批内和批间不精密度均<15%。样品在室温下至少稳定4小时，在 - 20°C下稳定2个月，在 - 70°C下稳定6个月，并且经过3次冻融循环后仍稳定。1 -、5 -、10 - 和50 - mcg/mL样品的萃取效率平均分别为2.2%、1.8%、1.6%和1.4%。
本文所述的用于分析羟基脲的同位素稀释GC - MS方法准确、灵敏、精密且稳健。其特性使该方法适用于支持药代动力学研究和/或临床治疗监测。
