A Rapid and Simple HPLC-MS/MS Method for the Quantitative Determination of Colistin for Therapeutic Drug Monitoring in Clinical Practice

Colistin is the last-line option for the treatment of multidrug-resistant gram-negative bacterial infections with narrow therapeutic window. It is essential to ensure its efficacy and safety by therapeutic drug monitoring (TDM). Quantitative determination of colistin is difficult due to its complex ingredients. Previous determination methods demand intricate sample pre-treatment which are not only time-consuming but also costly, and is difficult to apply in clinical practice. Therefore, in order to carry out quantitative determination of colistin accurately and quickly, we establish a rapid high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) with simple sample pre-treatment process. The sample was purified by acetonitrile to remove the plasma protein. Then purified colistin was effectively separated from terfenadine, an internal standard (IS) using Phenomenex Kinetex C18 column (50.0×2.1mm, 5µm) with acetonitrile and water mobile phase at a flow rate of 0.5 mL/min and 40°C column temperature. Colistin and IS were monitored in positive ion mode. Our method expressed good linearity in 50.0~6000 ng/mL of colistin B and 28.31~3397.51 ng/mL of colistin A in plasma. Methodology validations, including selectivity, precision, accuracy, recovery, stability, matrix effect, and dilution integrity met acceptance criteria of of the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH).