Development and validation of LC-ESI-MS/MS method for analysis of moxifloxacin and levofloxacin in serum of multidrug-resistant tuberculosis patients: Potential application as therapeutic drug monitoring tool in medical diagnosis

• LC-ESI-MS/MS method was developed and validated.
• MRM method was used for detection and quantification of target analytes.
• The developed method was applied in real serum sample analysis.
• Effective determination of MFX and EFX levels in serum of MDR-TB patients was achieved.

Moxifloxacin (MFX) and levofloxacin (LFX), class of fluoroquinolone antibiotics, are the two most prescribed drugs to multidrug resistant tuberculosis (MDR-TB) patients. A single, sensitive and reliable LC-ESI-MS/MS method was developed and validated to simultaneously quantitate the levels of these drugs in human serum where enrofloxacin (EFX) was used as internal standard (IS). Quantification was achieved by multiple reaction monitoring of selected mass transitions from precursor ions to product ions m/z 402.2 → 384.2 for MFX, 362.2 → 318.2 for LFX, and 362.1 → 318.3 for EFX. Calibration curves were plotted using concentrations ranging between 0.23–1000 ng/mL for MFX and 0.13–1000 ng/mL for LFX, and the correlation coefficients (r2) were in excess of 0.999. Intra- and inert-day accuracy was ranged between 92.1–104% with mean recoveries of 96% and 95.5% for MFX and LFX, respectively and precision was <9% at all quality control concentration levels. Matrix effect analysis showed extraction efficiency of 93.0–94.6% for MFX and 90.9–99.5% for LFX. Application of the developed method to real sample analysis resulted in efficient quantification of MFX and LFX in serum samples obtained from ten MDR-TB patients. The result indicated that the method could be applied as a potential drug monitoring tool to accurately analyze MFX and LFX within a short run time.