LC-MS/MS method for nine different antibiotics.

• HPLC–MS/MS method for the quantification of nine diverse antibiotics. • Includes trimethoprim-sulfamethoxazole, ciprofloxacin, ertapenem and five cephalosporins. • Unbound ertapenem and cefazolin can be measured after ultracentrifugation. • Extensive stability data are presented. • The method was implemented in routine TDM and in a clinical study. TDM of antibiotics can bring benefits to patients and healthcare systems by providing better treatment and saving healthcare resources. We aimed to develop a multi-analyte method for several diverse antibiotics using LC-MS/MS. Sample preparation consisted of protein precipitation with methanol, dilution and online extraction using a Turboflow Cyclone column. Separation was performed on a Synergi 4 µm Max RP column and deuterated forms of three antibiotics were used as internal standards. We present a LC-MS/MS method for the quantitative determination of nine antibiotics, including five cephalosporins, the carbapenem ertapenem, the fluoroquinolone ciprofloxacin as well as the combination drug trimethoprim-sulfamethoxazole from plasma. Additionally, unbound ertapenem and cefazolin were analyzed in plasma water after ultrafiltration using plasma calibrators. Results from routine TDM show the applicability of the method. The presented method is precise and accurate and was introduced in a university hospital, permitting fast TDM of all nine analytes. It was also used in a clinical study for measuring cefazolin free and total concentrations. [ABSTRACT FROM AUTHOR]