A high-performance liquid chromatography method with photodiode-array UV detection for therapeutic drug monitoring of the nontricyclic antidepressant drugs

A new rapid and sensitive high-performance liquid chromatography method has been developed for the screening and determination in human plasma of the 11 most commonly prescribed nontricyclic antidepressants and two metabolites: fluoxetine, norfluoxetine, sertraline, paroxetine, citalopram, fluvoxamine, moclobemide, mirtazapine, milnacipram, toloxatone, venlafaxine, desmethyl venlafaxine, and viloxazine. It involves liquid-liquid extraction procedures followed by liquid chromatography coupled to photodiode-array UV detection with three fixed wavelengths (220, 240, and 290 mn). Compounds were separated on a 5-mum Hypurity C-18 (ThermoHypersil) analytic column (250 x 4.6 mm W.) using a gradient of acetonitrile-phosphate buffer pH 3.8 at a flow rate of 1.0 mL/min. The total analysis time was only 18 min per sample. Extraction recoveries were in the 74-109% range for 11 compounds but were of only 59% for moclobemide and less than 10% for toloxatone. Calibration curves were linear in the 25 to 1000 ng/mL range for all compounds, all of them with coefficients of determination (r(2) values) greater than or equal to 0.999. Limits of detection (LODs) ranged from 2.5 to 5 ng/mL except for toloxatone (10 ng/mL). Intraassay and interassay precision and accuracy were studied at two concentration levels (50 and 500 ng/mL). The intraassay coefficients of variation (CVs) for all compounds were less than or equal to 7.6%, and all interassay CVs were below 11.5% except for mitnacipram (14.8%). The intraassay and interassay accuracies for all compounds were found to be within 88.4% and 105.9% at 50 ng/mL and within 87.2% and 100.5% at 500 ng/mL. The performance of the method allows the therapeutic drug monitoring of the most prescribed nontricyclic antidepressant drugs as well as its use in toxicologic screening.