Department of Laboratory Medicine, Division of Clinical Pharmacology, Karolinska Institutet; and.
Medical Diagnostics Karolinska, Medical Unit of Clinical Pharmacology, Karolinska University Hospital, Stockholm, Sweden.
Ther Drug Monit. 2023 Feb 1;45(1):45-54. doi: 10.1097/FTD.0000000000001016.
Ultrafiltration (UF) is a conventional method for isolating the protein-unbound plasma fractions of therapeutic drugs. However, the ideal UF conditions for specific compounds remain largely unexplored. By comparing UF-derived unbound concentrations with the corresponding results obtained using a reference method, the authors sought to identify appropriate UF conditions for cefotaxime, cloxacillin, flucloxacillin, and piperacillin.
In vitro microdialysis (MD) with a no-net-flux approach was used as a reference method for plasma protein separation, for which UF performance was assessed. Four levels of relative centrifugal force (2500-11,290 g ) and 2 levels of temperature (37 vs. 22°C) during 10 minutes of UF centrifugation were evaluated. Ultrafiltrates and reference microdialysates were analyzed using liquid chromatography-tandem mass spectrometry to obtain unbound concentrations. After identifying the appropriate UF conditions in the spiked plasma samples, exploratory analyses of clinical samples (n = 10 per analyte) were performed.
Of the evaluated UF alternatives, the best overall agreement with the MD-derived reference concentrations was obtained with 11,290 g UF performed at 22°C. For cloxacillin specifically, 37°C UF yielded better agreement than 22°C UF at 11,290 g. Clinical sample analyses indicated minimal differences between 22°C and 37°C at 11,290 g UF for cefotaxime and piperacillin. However, consistently lower levels of unbound cloxacillin (median: -23%, IQR: -19% to -24%) and flucloxacillin (median: -27%, IQR: -21 to -34%) were observed after UF at 22°C versus 37°C.
For the evaluated UF device, 10 minutes of 11,290 g UF at 22°C is appropriate for flucloxacillin, cefotaxime, and piperacillin, and can arguably be justified for cloxacillin as well for laboratory practice purposes. Maintenance of 37°C during high-centrifugal UF may lead to overestimation, particularly for unbound flucloxacillin.
超滤（UF）是一种分离治疗药物蛋白结合物的常规方法。然而，对于特定化合物的理想 UF 条件仍在很大程度上未被探索。作者通过比较 UF 衍生的游离浓度与使用参考方法获得的相应结果，旨在确定头孢噻肟、氯唑西林、氟氯西林和哌拉西林的合适 UF 条件。
使用无净流量微透析（MD）作为血浆蛋白分离的参考方法，评估 UF 性能。评估了 UF 离心 10 分钟时 4 个相对离心力（2500-11290g）和 2 个温度（37°C 与 22°C）水平。使用液相色谱-串联质谱法分析超滤滤出液和参考微透析液，以获得游离浓度。在确定了加标血浆样品中的合适 UF 条件后，对 10 个每个分析物的临床样品进行了探索性分析。
在所评估的 UF 替代方法中，与 MD 衍生的参考浓度最佳的整体一致性是在 22°C 下使用 11290g UF 获得的。具体而言，对于氯唑西林，在 11290g 时，37°C UF 比 22°C UF 产生更好的一致性。对于头孢噻肟和哌拉西林，在 11290g UF 时，22°C 和 37°C 之间的临床样品分析表明游离氯唑西林和氟氯西林的水平差异较小（中位数：-23%，IQR：-19%至-24%）和氟氯西林（中位数：-27%，IQR：-21%至-34%）在 22°C 下 UF 时观察到一致较低的水平。
对于评估的 UF 装置，在 22°C 下进行 10 分钟的 11290g UF 适用于氟氯西林、头孢噻肟和哌拉西林，并且从实验室实践的角度来看，也可以适用于氯唑西林。在高离心 UF 期间保持 37°C 可能导致过度估计，特别是对于游离氟氯西林。
