High-performance liquid chromatography with fluorescence detection method for measuring colistin in human serum and its application in critically ill patients treated with colistin methanesulfonate sodium

AbstractColistin, in the form of colistin methanesulfonate sodium (CMS), has a narrow therapeutic window, and colistin levels must be monitored during treatment. The aim of this study was to develop and validate a high-performance liquid chromatography-fluorescence detection (HPLC-FLD) method for measuring colistin in human serum. Colistin was extracted from human serum using trichloroacetic acid and methanol for protein precipitation, followed by in-solid phase extraction derivatization with 9-fluorenylmethyl chloroformate. HPLC-FLD system using a reverse-phase HPLC C18 column and a mobile phase consisting of acetonitrile, tetrahydrofuran, and water (80%:4%:16%) were used for the quantification of colistin A, colistin B, and polymyxin B (internal standard) in human serum. The extraction recoveries were between 71% and 103%. Linear calibration curves were obtained for colistin in concentrations from 0.3 to 8.0 μg/mL, with good fit (r2 = 0.9993). The lower limit of quantitation was 0.3 μg/mL. The intra- and inter-day precision of the assay was 0.5–5% and 3.5–9.4%, respectively. The accuracy ranged from 98% to 100%. This validated method was successfully applied to the analysis of serum-receiving CMS in critically ill patients. This method will be useful to assist colistin dosage adjustment based on individual blood colistin levels for optimization of colistin therapy.Keywords: Colistin methanesulfonate sodiumcolistincritically ill patientsHPLC-FLDTDM AcknowledgementThe authors would like to thank the Director General of Health Malaysia for his permission to publish this article. We would also like to acknowledge the recruited patients and family, nurses, and staff members of the intensive care unit of Hospital Raja Perempuan Zainab II, Kota Bahru for their cooperation in conducting the research. The authors would also like to acknowledge staff members of Laboratory Department of Pharmacology, School of Medical Sciences, Universiti Sains Malaysia for their support and help.Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThis study was supported by USM Bridging Grant No: 304.PPSP.6316240 and GIPS-PhD Grant No: 311/PPSP/4404810. The first author was supported by Malaysia Ministry of Health, Hadiah Latihan Persekutuan (HLP). Institute of Postgraduate Studies, Universiti Sains Malaysia