Zhang Mei, Moore Grant A, Chin Paul K L, Everts Richard, Begg Evan J
Department of Medicine, University of Otago-Christchurch, Christchurch.
Toxicology, Department of Specialist Biochemistry, Canterbury Health Laboratories, Christchurch.
Ther Drug Monit. 2018 Dec;40(6):682-692. doi: 10.1097/FTD.0000000000000555.
Pharmacokinetic studies and therapeutic drug monitoring of antibiotics require a simple, rapid, and reliable analytical method for monitoring the concentrations in plasma, including unbound concentrations for highly protein-bound drugs. The aim of the current work was to develop and validate a liquid chromatography-tandem mass spectrometry method for the simultaneous determination of total and unbound concentrations of 3 widely used β-lactam antibiotics (cefalexin, cefazolin, and flucloxacillin) and the often coadministered drug probenecid in human plasma, suitable for pharmacokinetic studies and for routine use in ordinary, busy hospital laboratories.
Unbound drug was separated from bound drug by ultrafiltration. A simple 1-step protein precipitation was used for sample preparation. Cefalexin, cefazolin, flucloxacillin, probenecid, and their corresponding isotopically labeled internal standards were then resolved on a C18 (2) column. All the compounds were detected using electrospray ionization in the positive mode.
Standard curves were linear for all compounds over the concentration range of 0.2-100 mg/L (r > 0.99) for total drug in plasma and 0.01-10 mg/L (r > 0.99) for unbound drug in plasma ultrafiltrate. For both total and unbound drugs, bias was <±10%, and intra- and interday coefficients of variation (imprecision) were <10%. The limit of quantification was 0.2 mg/L for total plasma concentrations and 0.01 mg/L for plasma ultrafiltrate concentrations of all drugs.
The method has proven to be simple, rapid, robust, and reliable and is currently being used in clinical pharmacokinetic studies and in the routine clinical service to enhance the effective use of the β-lactam antibiotics.
抗生素的药代动力学研究和治疗药物监测需要一种简单、快速且可靠的分析方法来监测血浆浓度，包括高蛋白结合率药物的游离浓度。本研究的目的是开发并验证一种液相色谱 - 串联质谱法，用于同时测定人血浆中3种广泛使用的β - 内酰胺类抗生素（头孢氨苄、头孢唑林和氟氯西林）以及常与之联用的药物丙磺舒的总浓度和游离浓度，该方法适用于药代动力学研究以及普通繁忙医院实验室的常规使用。
通过超滤将游离药物与结合药物分离。采用简单的一步蛋白沉淀法进行样品制备。然后，头孢氨苄、头孢唑林、氟氯西林、丙磺舒及其相应的同位素标记内标在C18（2）柱上分离。所有化合物均采用正模式电喷雾电离进行检测。
血浆中总药物浓度范围为0.2 - 100 mg/L（r > 0.99），血浆超滤物中游离药物浓度范围为0.01 - 10 mg/L（r > 0.99）时，所有化合物的标准曲线均呈线性。对于总药物和游离药物，偏差均<±10%，日内和日间变异系数（不精密度）均<10%。所有药物的血浆总浓度定量限为0.2 mg/L，血浆超滤物浓度定量限为0.01 mg/L。
该方法已被证明简单、快速、稳健且可靠，目前正用于临床药代动力学研究和常规临床服务，以提高β - 内酰胺类抗生素的有效使用。
