Determination of levofloxacin in human serum using liquid chromatography tandem mass spectrometry

A rapid liquid chromatography tandem-mass spectrometry method was developed for the determination of levofloxacin and its metabolite (desmethyl-levofloxacin) in human serum. Sample preparation was done using protein precipitation technique. Our method had a run time of 2.5 min and retention times of 1.6 min for all analytes. The standard curves were linear within the concentration range of 0.10 to 5.00 mg/L for levofloxacin and 0.10 to 4.99 mg/L for desmethyllevofloxacin; a correlation coefficient (R2) of 0.999 and 0.998 respectively. The lower limit of quantification for both analytes was 0.10 mg/L. Within-day precision ranged from 1.4% and 2.4% for levofloxacin, 1.5% to 5% for desmethyl-levofloxacin and between-day precision ranged from 3.6% to 4.1% for levofloxacin and 0.0% to 3.3% for desmethyl-levofloxacin; whereas, accuracy ranged from 0.1% to 12.7% for levofloxacin and 0.2% to 15.6% for desmethyl-levofloxacin. This method could be a useful asset for routine therapeutic drug monitoring of levofloxacin in multi-drug resistant tuberculosis patients.