Development of a Method of Liquid Chromatography Coupled with Tandem Mass Spectrometry for Simultaneous Determination of Linezolid and Tedizolid in Human Plasma

It is important to select appropriate antibiotics for infection control. Linezolid and tedizolid are newly developed and synthesized oxazolidinone antibacterial agents. It has been pointed out that there is a relationship between a high plasma concentration of the target drug and incidence of adverse effects, although it has been reported that neither linezolid nor tedizolid requires dose adjustment according to renal function. Due to the high incidence of adverse effects, both are often switched. Precise plasma concentration control by therapeutic drug monitoring (TDM) is desirable for reducing the adverse effects of both drugs and obtaining a better therapeutic effect. In this study, we aimed to establish a method for simultaneous quantification of linezolid and tedizolid in human plasma using LC coupled with tandem mass spectrometry. Sample preparation was performed by a simple operation with acetonitrile. Linezolid and tedizolid were separated by an octadecylsilyl column using a gradient elution of acetonitrile in aqueous 0.1% formic acid solution and were detected in the positive ion electrospray mode with multiple reaction monitoring. Quantification of linezolid and tedizolid ranged from 0.5 to 50 and 0.5 to 20µg/mL, respectively. The intra-day and inter-day precision and accuracy of data were assessed and found to be acceptable. The developed method was successfully applied to measurement of the concentrations of linezolid and tedizolid. This simple method, which can simultaneously quantify both drug concentrations for daily TDM, could contribute to safer treatment of patients.