Determination of ertapenem in plasma and ascitic fluid by UHPLC-MS/MS in cirrhotic patients with spontaneous bacterial peritonitis

Objectives: Spontaneous bacterial peritonitis is a frequent severe complication in cirrhotic patients with ascites. Carbapenem antibiotics are currently the treatment of choice for patients with hospital-acquired or healthcare-related infections. However, there is limited evidence available on the efficacy of ertapenem in cirrhotic patients with spontaneous bacterial peritonitis. As a result, the pharmacokynetics and pharmacodynamics of this antibiotic are still unknown. The objective of this study was to develop and validate measurement procedures based on liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) to determine ertapenem concentrations in plasma and ascitic fluid.Methods: Samples were pretreated by acetronile protein-precipitation. Chromatographic separation is performed on a C18 reversed-phase Acquity (R)-UPLC (R)-BEHTM column (2.1 x 100 mm id, 1.7 mu m) using a non-linear gradient of water/acetonitrile containing 0.1 % of formic acid at a flow rate of 0.4 mL/min. Ertapenem and its internal standard (ertapenem-D4) are detected by tandem mass spectrometry using positive electrospray ionization and multiple reaction monitoring, and using 476.2 -> 346.0/432.2 as mass transition for ertapenem and 480.2 -> 350.0 for its internal standard.Results: No significant interferences or carry-over contamination were observed. Imprecisions, absolute relative bias, matrix effects and normalized recoveries were <= 14.5 %, <= 9.3 % (92.8-104.5) % and (98.8-105.8) %, respectively. Chromatographic measurement procedures were linear from (0.50-100) mg/L.Conclusions: The measurement procedures based on UHPLC-MS/MS developed and validated in this study could be useful in pharmacokynetic and pharmacodynamic studies in subjects with liver cirrhosis who develop spontaneous bacterial peritonitis treated with ertapenem.