Determination of colistin A and colistin B in human plasma by UPLC-ESI high resolution tandem MS: application to a pharmacokinetic study.

The resistance of gram-negative bacteria to most available antibiotics and the lack of new antimicrobial agents have prompted the re-emergence of colistin (CS) as potent treatment against most gram-negative microorganisms. Optimal dosing with CS suffers from poor pharmacokinetic characterization mainly due to the analytical challenge of assaying CS in biological fluids and the limited information on quantitative analysis of CS in plasma using high resolution mass spectrometry (MS). Hence, a rapid, simple and accurate analytical method based on ultra performance liquid chromatography (UPLC) combined with electrospray ionization (ESI) tandem mass spectrometry (MS/MS) on a hybrid quadrupole time of flight (QTOF) instrument has been developed and fully validated for the quantification of CS in human plasma.