Simultaneous Determination of Contezolid and Its Metabolite M2 in Human Plasma and Cerebrospinal Fluid by Ultra-High-Performance Liquid Chromatography – Tandem Mass Spectrometry (UHPLC-MS/MS)

This study established a simple, rapid, and sensitive ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for the simultaneous quantification of contezolid and its major metabolite M2 in human plasma and cerebrospinal fluid (CSF). We used isotope-labeled internal standards (IS) along with protein precipitation to efficiently eliminate impurities. The ion transition was m/z 409.1 → 269.1 for contezolid, m/z 414.1 → 269.0 for contezolid-d5, m/z 445.1 → 385.1 for M2, and m/z 450.2 → 390.1 for M2-d5. The flow rate was 0.4 mL/min with a run time of 2.5 min. Validation results demonstrated that the calibration range was 10–5000 ng/mL for contezolid, and 5–2500 ng/mL for M2 in plasma and CSF. Both analytes exhibit excellent linear relationships (all R2 ≥ 0.99). Intra- and inter-batch accuracy and precision for all quality control (QC) levels were within ± 15%, including the lower limit of quantification (LLOQ). The recoveries of contezolid and M2 were 92.60–100.4% and 92.26–99.61% in plasma and 93.33–99.19% and 91.31–98.21% in CSF, respectively. The matrix effects for contezolid and M2 were 97.20–110.3% and 98.27–105.47% in plasma and 105.25–112.99% and 103.35–109.84% in CSF, respectively. The coefficients of variation (CV%) were ≤ 12.58%. Conteozolid and M2 remained stable in plasma and CSF. This study has established a simple and accurate method for determining contezolid and M2 in human plasma and CSF, making it a valuable tool for monitoring the efficacy of central nervous system (CNS) drugs.