A Novel LC-MS/MS Method for the Analysis of Antibiotics in Plasma for Clinical Research

Importance of the Topic

Reliable analysis of antibiotics in plasma is critical for understanding their pharmacokinetics and pharmacodynamics in clinical research. Multiplexed assays enable efficient monitoring of multiple drugs simultaneously.

Study Objectives and Overview

This work aimed to develop and validate a rapid LC-MS/MS method capable of quantifying a broad panel of 17 antibiotics in human plasma across varied concentration ranges.
The panel includes antibiotics with calibration ranges as follows:

• Azithromycin: 5–500 ng/mL
• Ciprofloxacin, Clindamycin: 0.1–10 μg/mL
• Ampicillin, Cefotaxime, Chloramphenicol, Linezolid: 0.5–50 μg/mL
• Cefazolin, Cefepime, Ceftazidime, Cefuroxime, Flucloxacillin, Meropenem, Sulbactam: 1–100 μg/mL
• Daptomycin, Piperacillin: 2–200 μg/mL

Methodology and Instrumentation

Sample preparation involved protein precipitation of 50 μL plasma with methanol containing internal standards. Chromatographic separation was achieved using a water/methanol/ammonia gradient on a BEH C18 column in a 5-minute run with polarity switching mass spectrometric detection.

Used Instrumentation

• Waters ACQUITY UPLC I-Class FTN system
• Waters ACQUITY UPLC BEH C18 column (2.1 × 1.7 μm, 100 mm)
• Waters Xevo TQD triple quadrupole mass spectrometer

Main Results and Discussion

No carryover was observed at the highest calibrator concentrations. The method achieved lower limits of quantification with ≤20% coefficient of variation and ≤15% bias. Intra- and inter-day precision (n=25) were ≤12.5% RSD. Calibration curves provided first or second order polynomial fits with correlation coefficients ≥0.995. Post-column infusion experiments demonstrated minimal matrix effects, and internal standards compensated for residual suppression or enhancement.

Benefits and Practical Applications

• Multiplexed quantification of multiple antibiotics in a single 5-minute run
• High precision and accuracy across a wide concentration range
• Robust performance against matrix effects and potential interferences

Future Trends and Applications

Expanding the panel to include additional antimicrobials, integrating automated sample preparation, and implementing high-throughput designs can accelerate clinical pharmacology studies and therapeutic drug monitoring.

Conclusion

The presented LC-MS/MS method offers a fast, precise, and robust solution for multiplexed antibiotic analysis in plasma, supporting advanced clinical research on drug behavior and dosing strategies.

References

Ballantyne D. A Novel LC-MS/MS Method for the Analysis of Antibiotics in Plasma for Clinical Research. Waters.