An ultra-high pressure liquid chromatography high-resolution mass spectrometric (UHPLC-HRMS) method was developed for the simultaneous and sensitive quantification of 10 β-lactam antibiotics (cefepime, meropenem, amoxicillin, cefazolin, benzylpenicillin, ceftazidime, piperacillin, flucloxacillin, cefuroxime and aztreonam), linezolid and β-lactamase inhibitors tazobactam and clavulanic acid in human plasma. Validation according to the EMA guidelines showed excellent withinand between-run accuracy and precision (i.e. between 1.1 and 8.5%) and high sensitivity (i.e. lower limit of quantification between 0.25 and 1 mg/L). The UHPLC-HRMS method enables a short turnaround time and high sensitivity and needs only a small amount of plasma, allowing appropriate routine therapeutic drug monitoring.The short turnaround time is obtained by speeding up the protocol on multiple levels, i.e. fast and workload-efficient sample preparation (i.e. protein precipitation and dilution), short (4 min) instrument run time, simultaneous measurement of all relevant β-lactam antibiotics used in the intensive care unit and the use of the same instrument, column and mobile phases as for the other routine methods in our laboratory.
K E Y W O R D Sβ-lactam antibiotics, HRMS, therapeutic drug monitoring
| INTRODUCTIONSevere infection and associated septic shock persist as significant healthcare concerns as they are the most common cause of mortality in critically ill patients worldwide (Vincent et al., 2009). Since adequate and early administration of antibiotics remains the mainstay of therapy for the treatment of severe infections, there is a high level of consumption of antibiotics in intensive care units (ICU) (Dellinger et al., 2013). A single-day point prevalence study showed that 71% of the ICU patients received antimicrobial therapy (Vincent et al., 2009). However, in specific patient populations like critically ill patients, cystic fibrosis patients, elderly patients, neonates, etc., the pharmacokinetics of these antibiotics may be profoundly disturbed owing to pathophysiological changes in distribution and elimination (Roberts et al., 2014;Taccone et al., 2010;Theuretzbacher, 2012). Consequently, an empirical fixed dose approach, in which every patient is treated according to the same dosing scheme, appears to be inadequate and can lead to excessive drug exposure with an increased risk of toxicity or inadequate drug exposure with clinical failure and/or antimicrobial resistance (Roberts & Lipman, 2006). Optimizing antibiotic dosing may be a key intervention, not only to improve clinical outcome and minimize toxicity, but also to prolong the clinical lifespan of the currently available antibiotics by limiting the emergence of