ABSTRACT
Meropenem is a broad-spectrum antibiotic, often used for the empirical treatment of infections in critically ill patients with acute kidney injury. Meropenem has clinically insignificant protein binding and, as a carbapenem antibiotic, shows time-dependent bacterial killing, meaning that the unbound or free antibiotic concentration in blood should be maintained above the minimal inhibitory concentration of the pathogen for at least 40 % of the dosing interval. We developed and validated simple chromatographic methods by ultra-performance liquid chromatography-tandem mass spectrometry to measure plasma, filtrate-dialysate, and urine concentrations of meropenem. Chromatographic separation was achieved using an Acquity(®) UPLC(®) BEH(TM) (2.1 × 100 mm id, 1.7 µm) reverse-phase C(18) column, with a water/acetonitrile linear gradient containing 0.1 % formic acid at a 0.4-mL/min flow rate. Meropenem and its internal standard (ertapenem) were detected by electrospray ionization mass spectrometry in positive ion multiple reaction monitoring mode. The limits of quantification were 0.27, 0.24, and 1.22 mg/L, and linearity was observed between 0.27-150, 0.24-150, and 1.22-2,000 mg/L for plasma, filtrate-dialysate, and urine samples, respectively. Coefficients of variation and relative biases were less than 13.5 and 8.0 % for all biological fluids. Recovery values were greater than 68.3 %. Evaluation of the matrix effect showed ion suppression for meropenem and ertapenem. No carry-over was observed. The validated methods are useful for both therapeutic drug monitoring and pharmacokinetic studies. It could be applied to daily clinical laboratory practice to measure the concentration of meropenem in plasma, filtrate-dialysate, and urine.