Therapeutic monitoring of tricyclic antidepressants in plasma by gas chromatography.

We describe a comprehensive gas chromatographic analysis for therapeutic concentrations of amitriptyline, nortriptyline, imipramine, desipramine, doxepin, and desmethyldoxepin in plasma, with use of a nitrogen detector. All these drugs are extracted and chromatographed under identical conditions. Each tertiary amine tricyclic is well resolved from its secondary amine metabolite on a mixed-phase column and the concentrations of both are determined simultaneously, without derivatization. The lower limit of sensitivity is 10 microgram/liter of plasma (2-ml sample). Analytical recoveries of the tertiary and secondary amines are 100 and 80%, respectively. Between-run CV's for all of the drugs ranged between 5 and 7%.