Method Development and Validation for the Determination of Linezolid Drug in Human Plasma by Reversed-Phase High-Performance Liquid Chromatography

Objective: Linezolid is a significant antibiotic used against severe infections initiated by multi-resistant bacterial pathogens. Aims: The aim of this study is to develop and validate a simple, selective and accurate highperformance liquid chromatographic HPLC method for the analysis of linezolid LZD. Methods: Linezolid extraction from plasma is obtained using methanol. Chromatographic separation is achieved isocratically on a C18 column [Zorbax C18, 5 μm particle size, 150 mm* 4.6 mm] making use of a mobile phase of acetonitrile / 0.05 M phosphate buffer, pH = 4.5 (30: 70 v/v) at a flow rate of 1.2 mL/min with photodiode array detector DAD, at a wavelength of 256 nm. Results: The retention time of linezolid was 2.5 min. The analytical method was linear (r² > 0.998) over the calibration range of 0.30 to 50.0 μg/mL. The extraction recoveries of linezolid range from 71.03 to 91.93 %. The limit of quantification and the limit of detection were 0.112 μg and 0.037 μg, respectively. The RSDs for intraday and interday assays were < 7.77 and 4.32 %, respectively. The intraday and interday accuracies were in the range 80.6-112 % and 77.44- 104.85 %, respectively. Conclusion: The applied method is precise, accurate and appropriate for pharmacokinetic studies and therapeutic drug monitoring of linezolid in routine clinical practice.