HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY METHOD FOR ANALYZING CITALOPRAM AND DESMETHYLCITALOPRAM FROM HUMAN SERUM

This report describes a sensitive and specific method for analyzing a serotonin reuptake blocker, citalopram, and its active metabolite, des methylcitalopram, in human serum. For high-performance liquid chromato graphy (HPLC) analysis, samples and standards are prepared with ASPEC automatic sample preparator using 100 mg Bond-Elut C-18 solid-phase ex traction columns. The method is an isocratic HPLC method with a mobile phase of acetonitrile : methanol : 50 mM dipotassium hydrogenphosphat e, pH 4.7 (40:100). Detection is performed with diode array detector a t 220 nm and the peak purity analyses at 210 to 365 nm. The intraassay coefficient of variation ranges from 3.7% to 7.3%, and the interassay coefficient of variation ranges from 6.9% to 9.9% at therapeutic drug concentrations. The detection limit is 15 nmol/l. The method is suita ble for therapeutic drug monitoring in a clinical laboratory. A clear correlation, r = 0.72 (y = 0.36x + 17.94), between citalopram and its metabolite levels is observed in routine therapeutic drug monitoring s ervice. A linear correlation between serum concentration and daily dos e of citalopram in patient groups is also observed.