Determination of the antidepressants maprotiline and amoxapine, and their metabolites, in plasma by liquid chromatography.

Abstract

Abstract Maprotiline, amoxapine, and their metabolites were determined in plasma by three separate procedures, each of which involves a three-step extraction followed by reversed-phase separations. Amoxapine, maprotiline, and N-desmethylmaprotiline can be measured with use of a conventional C-18 column with 10% carbon load, but analyses for 7- and 8-hydroxyamoxapines require a small (5-microns) particle size, high carbon load, 20% C-18 column with 0.2 mol/L phosphate as mobile phase. Within-run and day-to-day CVs were 5% and 8%, respectively. Peak-height ratios were linearly correlated with concentrations between 0 and 400 micrograms/L. Detection limits ranged from 1 to 3 ng. Interference studies indicated that nortriptyline co-elutes with maprotiline. Assays of patients' plasma showed substantial amounts of these drugs and most of their metabolites, but only trace amounts of 7-hydroxyamoxapine.