Liquid Chromatography-Tandem Mass Spectrometry to Monitor Unbound and Total Ceftriaxone in Serum of Critically Ill Patients.

Abstract

Ceftriaxone is recommended for empiric antimicrobial therapy in patients with sepsis. Therapeutic Drug Monitoring (TDM) guided dose optimisation could elucidate pharmacokinetic variabilities, improving treatment efficacy. However, detailed data on Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS) for unbound ceftriaxone quantification in serum are scarce. The authors aimed to develop a reliable UPLC-MS/MS method for serum ceftriaxone quantification and exhibit its application potential in routine hospital settings. In this observational, single centre study, UPLC-MS/MS method validation included specificity, carry-over, linearity, repeatability, intermediate precision, accuracy, the limit of quantification, and plasma protein binding. Unbound and total ceftriaxone were quantified in the serum of 5 critically ill patients. Pharmacokinetic/Pharmacodynamic (PK/PD) target attainment calculations were performed for both unbound and total ceftriaxone. The PK/PD target for unbound ceftriaxone in serum was set at 4 times the non-species related minimum inhibitory concentration breakpoint of 1 mg/L for at least 60% of the dosing interval. The UPLC-MS/MS method revealed acceptable limits for clinical samples, with coefficients of variation < 15.0% for concentrations between 0.2 - 400.0 mg/L. Ceftriaxone eluted at 1.94 min and ceftazidime, as internal standard, eluted at 1.42 min. Patients demonstrated a median unbound ceftriaxone fraction of 29.1% (IQR: 15.2 - 52.2). Day 1 of ceftriaxone treatment presented a median PK/PD target attainment of 100.0% (IQR: 81.1 - 100.0) for unbound ceftriaxone in serum, while for calculations based on total concentrations, this figure was 23.9% (IQR: 10.5 - 80.6). The described UPLC-MS/MS method enables reliable and rapid ceftriaxone quantification in the serum of critically ill patients. Method feasibility was exhibited for TDM purposes in routine clinical practice.