Quantification of beta-lactam antibiotics cefuroxime and flucloxacillin in human synovial fluid, using ultra-performance convergence chromatography-tandem mass spectrometry

Total hip- and knee arthroplasty generally result in successful outcomes. A small percentage of patients however suffer from periprosthetic joint infections (PJI) postoperatively, often with severe consequences. The standard treatment of chronic PJIs consists of a staged arthroplasty exchange during which antibiotic therapy plays a crucial role. For successful antibiotic treatment, adequate concentrations at the infection site are a prerequisite. Regarding the treatment of PJIs, knowledge is lacking with respect to the relationship between administered dosages and plasma- and infection site concentrations of the antibiotics. To gain insight into the antibiotic exposure at the infection site, validated analytical methods for analysis of the antibiotics in matrices at the site of the PJI are essential. We describe a validated ultra-performance convergence chromatography-tandem mass spectrometry (UPC²-MS/MS) method for quantification of the beta-lactam antibiotics cefuroxime and flucloxacillin in synovial fluid. This method was successfully validated for antibiotic quantification in synovial fluids according to the EMA guidelines and consists of a simple sample preparation. For both antibiotics, the accuracy and precision were within requirements (RSD < 15%). In addition, matrix effects and recovery were within the range of 80-120%. Carry over was less than 20% and stability in -80 °C was at least 2 months for standards and quality controls. The limits of quantification were adequate (1-100 mg/L) to cover potential cefuroxime and flucloxacillin concentrations in synovial fluid as described in literature (r > 0.995). The method has a run time of 4.5 min and 50 μL synovial fluid is needed and the validated method will be applied during a PK/PD study to determine the exposure of the study antibiotics in synovial fluid at the site of PJIs.