Simultaneous analysis of citalopram and desmethylcitalopram by liquid chromatography with fluorescence detection after solid-phase extraction

Objectives: To develop a HPLC method for the determination of citalopram (CIT) and desmethylcitalopram (DCIT). Methods: Solid-phase extraction followed by fluorescence detection was used to measure CIT and DCIT in deproteinized plasma. Results: The extraction recovery for both analytes was 104 +/- 3%. The calibration was linear over the concentration range of 12-1600 ng/mL for CIT and 6-800 ng/mL for DCIT. The within-run CVs were 2.5% for CIT (400 ng/mL) and 2.9% for DCIT (200 ng/mL) and the between-run CVs were 5.2% for CIT and 2.9% for DCIT, respectively. With low concentrations of CIT (50 ng/mL) and DCIT (25 ng/mL), the within-run CVs were 3.1% and 1.1% and the between-run CVs were 7.4% and 8.8%, respectively. The lower limit of quantification was 12 ng/mL for CIT and 6 ng/mL for DCIT. Conclusions: This method allows for the simultaneous determination of CIT and DCIT in plasma at therapeutic and toxic drug concentrations. (C) 2005 The Canadian Society of Clinical Chemists. All rights reserved.