Simultaneous measurement of piperacillin, tazobactam and meropenem in patient samples using LC-MS/MS to support β-lactam therapeutic drug monitoring.

Background

accurate therapeutic drug monitoring (TDM) of β-lactam antibiotics such as meropenem and piperacillin-tazobactam is essential in critically ill patients, where profound pharmacokinetic variability may lead to subtherapeutic exposure or toxicity. Practical, high-throughput analytical workflows are needed to support timely dose optimisation in routine clinical settings.

Methods

we developed and fully validated a unified LC-MS/MS method for the simultaneous quantification of meropenem, piperacillin, and tazobactam in human serum. Samples were prepared by protein precipitation and analysed on a C18 column using a water/methanol gradient with 0.1% formic acid. Detection was performed by multiple reaction monitoring with isotopically labelled internal standards.

Results

the assay demonstrated excellent linearity (R2 > 0.998), high sensitivity (LLOQ 0.02 mg L-1), and robust intra- and inter-day precision (<10%), with a 10 min run time and no detectable carry-over. The method demonstrates high analytical sensitivity, with a lower limit of quantification (LLOQ) of 0.02 mg L-1 for all analytes, which is among the lowest reported for simultaneous quantification of meropenem, piperacillin, and tazobactam. Application to >40 clinical samples from critically ill patients revealed wide concentration ranges (meropenem 0.2-270 mg L-1; piperacillin 1-580 mg L-1; tazobactam 0.1-60 mg L-1), with unbound fractions consistent with published data.

Conclusions

this streamlined, low-volume LC-MS/MS workflow enables rapid, accurate quantification of key β-lactam antibiotics and supports routine TDM in critically ill and paediatric populations, facilitating more individualised antimicrobial dosing in clinical practice. Since our method already accommodates β-lactams and a β-lactamase inhibitor with highly heterogeneous physicochemical properties, it provides a robust basis for extending the approach to additional antibiotics within a multi-analyte framework.