LC-MS/MS method for simultaneous quantification of antibiotics in dialysis effluent and human serum for routine therapeutic drug monitoring.

Accurate drug dosing in critically ill patients, especially those undergoing continuous renal replacement therapy (CRRT), poses significant challenges due to altered pharmacokinetics. These changes increase the risk of treatment failure, toxicity, and resistance, emphasizing the need for precise and timely therapeutic drug monitoring (TDM) and improved analytical techniques. Therefore, this study aimed to develop and validate a multiplex LC-MS/MS method for the routine quantification of 4 antibiotics (cefepime, levofloxacin, meropenem, and piperacillin) and a β-lactamase inhibitor (tazobactam) in human serum and CRRT effluent. Effluent and serum samples were prepared via protein precipitation, and quantification was performed using LC-MS/MS, utilizing a gradient of aqueous (water, acetonitrile, formic acid) and organic (acetonitrile, 2-propanol) phases, with a total run time of 6.5 min. The method employed identical calibration and quality control sets for both serum and effluent. Calibration curves were linear across compound-specific ranges. The method met the validation criteria, showing reproducibility with CV ≤ 10.6%, a mean recovery of 102.2% in serum and 99.1% in effluent, and an accuracy ranging from 94.7% to 98.9% in serum and 99.5% to 103.0% in effluent. Carry-over effects observed for levofloxacin and piperacillin and compounds' stability were effectively managed through proper sample handling procedures. The developed method confirms its suitability for routine clinical application, providing a reliable tool for antibiotics TDM in critically ill patients. Additionally, measuring drug concentrations in CRRT effluent offers valuable insights into drug clearance and pharmacokinetics, which could ultimately lead to better patient management and more tailored, effective treatments in the future.