High-performance liquid chromatographic assay with fluorescence detection for the routine monitoring of the antidepressant mirtazapine and its demethyl metabolite in human plasma.

A validated HPLC method for the simultaneous quantitative analysis of the antidepressant mirtazapine and its demethyl metabolite in human plasma is described. The active constituents including internal standard were extracted from 1 ml of plasma with hexane and separated on a muBondapak Phenyl column with fluorescence detection. The lower limit of quantification was 0.5 ng/ml, without significant interferences with endogenous or exogenous components. Inter- and intra-assay accuracy determined at quality control levels of 2, 10 and 80 ng/ml were, respectively, 104.6-113.7% and 105.1-117.7% for mirtazapine, and 91.7-99.3% and 89.9-103.7% for demethylmirtazapine. In all cases the precision was below 6.8%.