A validated ultra-performance liquid chromatography-tandem mass spectrometry method for the quantification of polymyxin B in mouse serum and epithelial lining fluid: application to pharmacokinetic studies.

OBJECTIVES

A rapid, sensitive and robust ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed for the quantification of four major polymyxin B components (polymyxin B1, polymyxin B2, polymyxin B3 and isoleucine-polymyxin B1) in serum and epithelial lining fluid (ELF) samples.

METHODS

A Waters Acquity UPLC HSS C18 column was used with 0.1% formic acid in water/acetonitrile as mobile phases. Analysis was performed in a positive ionization mode with multiple-reactions monitoring scan type. Five percent trichloroacetic acid was used to precipitate proteins in biological samples and to increase the sensitivity of detection.

RESULTS

Our results showed a linear concentration range of 0.0065-3.2 mg/L for all the major polymyxin B components in both serum and ELF, respectively; the interday variation was <10% and the accuracy was 88%-115%. The validated method was used to characterize the pharmacokinetics (serum and ELF) of polymyxin B in mice.

CONCLUSIONS

This is the first report, to date, examining the individual pharmacokinetics of various polymyxin B components in mice. Our results revealed no considerable differences in clearances among the components. The limited exposure of polymyxin B in ELF observed was consistent with the less favourable efficacy of polymyxin B reported for the treatment of pulmonary infections. This method can be used to further examine the pharmacokinetics of polymyxin B in a variety of clinical and experimental settings.