Therapeutic monitoring of serum digoxin for patients with heart failure using a rapid LC-MS/MS method

Objective: Here we develop a liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the determination of digoxin in serum. Design and methods: The serum samples were extracted with methyl tert-butyl ether using an isotope-labeled digoxin-d3 as internal standard. The analyte was separated on a reverse phase Capcell C18 column and detected in positive electrospray ionization multiple reaction monitoring mass spectrometry. Results: The chromatographic analysis was carried out within 3 min, but the complete analysis took longer because of the liquid-liquid extraction. The lower limit of quantification was 0.1 ng/mL for digoxin. The intra- and inter-batch precisions were less than 12%, and the bias ranged from -9.1% to 10.7%. The external quality assessment (EQA) results obtained with the LC-MS/MS method were comparable to target values. Subsequently, this method has been applied to the therapeutic monitoring of digoxin in a clinical setting. Conclusion: In this study, we have developed a rapid and reliable LC-MS/MS method for the therapeutic monitoring of digoxin in human serum. (C) 2009 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.