Objectives: The antibiotic teicoplanin, used for the treatment of infections caused by Gram-positive bacteria, is highly bound to plasma proteins (percentage protein binding, %PB, around 90%) and therapeutic plasma levels of total teicoplanin are 10-100 mg/L. Because of the low free concentrations (i.e. <1-10 mg/L), current immunoassays are not able to quantify free teicoplanin concentrations, although they might be more relevant in therapeutic drug monitoring than total concentrations.
Design and methods: In this study, an ultra-high performance liquid chromatography - high resolution mass spectrometry (UHPLC-HRMS) method for the quantification of total and free teicoplanin in K2EDTA plasma samples was developed and validated. Furthermore, %PB obtained by ultrafiltration was compared with that obtained by equilibrium dialysis using spiked samples from healthy subjects. Analytes were separated using a phenylhexyl column, gradient mobile phase analysis was used, total run time was 4.5 min and teicoplanin was detected by orbitrap MS.
Results: The precision and accuracy were below 15% and within ±15%, respectively and teicoplanin was found to be stable for at least 14 days in plasma at 4 °C. The %PB of teicoplanin in spiked plasma from healthy subjects as obtained by ultrafiltration (94.1 ± 1.3%) was in good agreement with that obtained by equilibrium dialysis (93.6 ± 0.4%), whereas mean %PB of teicoplanin in samples from infected patients who received the antibiotic was 87.7 ± 4.2% (range: 79.6-95.4%).
Conclusion: A novel highly sensitive UHPLC-HRMS method was developed and validated for the quantification of total and free teicoplanin in human K2EDTA plasma samples. Amongst others, this method is suitable for therapeutic drug monitoring.
Keywords: Free fraction; High resolution mass spectrometry; Orbitrap; Teicoplanin; Ultra-high performance liquid chromatography; Ultrafiltration.
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