Simultaneous Determination of Clomipramine and Its Demethylated Metabolite in Plasma and Erythrocytes by High-Performance Liquid Chromatography

Clomipramine and its N-demethylated metabolite, N-demethyl-clomipramine were determined simultaneously in plasma or in erythrocytes by a simple hexane-diethyl ether-step extraction procedure followed by reversed-phase liquid chromatography. Baseline separation was achieved by a 5-mu m cyanopropylsilane column. The mobile phase consisted of 10mM phosphate buffer-methanol-acetonitrile (25:15:60, v/v/v), at a flow rate of 1.2 ml/min. The eluant was monitored by a UV detector operating at 220 nm. The inter- and intra assay coefficients of variation were within 3.6 and 6.0 % for clomipramine and 4.1 and 6.5 % for N-demethyl clomipramine, respectively. The lowest limit of detection of clomipramine and N-demethylated clomipramine was 5 ng/ml. The method is sensitive, specific and allows for routine analysis in therapeutic controls of patients treated by this antidepressant