1 3 DOI 10.1007/s10337-017-3240-3 Chromatographia ORIGINAL Simultaneous Quantification of Antidepressants and Metabolites in Urine and Plasma Samples by GC–MS for Therapeutic Drug Monitoring Tiago Rosado 1 · Alexandra Gonçalves 1 · Ana Martinho 1 · Gilberto Alves 1,2 · Ana Paula Duarte 1 · Fernanda Domingues 1 · Samuel Silvestre 1,2 · Luiza Breitenfeld Granadeiro 1 · Víctor Oliveira 3 · Carlos Leitão 3 · Eugenia Gallardo 1 Received: 6 July 2016 / Revised: 13 November 2016 / Accepted: 9 January 2017 © Springer-Verlag Berlin Heidelberg 2017 Keywords Antidepressant drug · Metabolite · Biological sample · GC/MS · SPE Introduction Depression is a chronic or recurrent severe mental illness that impairs both social and occupational functions of an individual, and can eventually lead to suicidal behavior [1, 2]. It is characterized by a persistent and unreactive low mood and by a marked loss of interest and desire, regularly accompanied by sleep disturbance, fatigue, inappropriate guilt, and dark thoughts of death [3, 4]. To treat this disor- der, medication and psychological therapies are both effec- tive, but antidepressant drugs (ADs) are the most common treatment for moderate to severe major depression [3, 5]. They have all been prescribed over the past several dec- ades to treat major depressive disorder [6]. Tricyclic anti- depressants were used initially, between 1960 and 1980, for the treatment of depression; however, the introduction of numerous “new” ADs, called second generation [1], has replaced classical ADs as first-line choices in depres- sion treatment due to similar efficacy and fewer side effects [7, 8]. Today, psychiatric medication is prescribed in sev- eral combinations, leading to potential drug interactions, while the dose is essentially based on trial and error [1]. For these reasons, and because those drugs show large indi- vidual differences in clearance, while therapeutic windows are relatively small, therapeutic drug monitoring (TDM) of ADs could be of interest for monitoring patient com- pliance [1, 9]. TDM of psychotropic medicines is a mul- tidisciplinary area that allows several professional classes (pharmacologists, clinicians, and laboratory specialists) to co-operatively optimize medical treatment for a psychiat- ric disorder, personalizing drug dosages [8, 10–13], also Abstract The aim of this work was the optimization and method validation for antidepressants (fluoxetine, venla- faxine, amitriptyline, mianserin, trimipramine, nortrip- tyline, mirtazapine, sertraline, dothiepin, citalopram, and paroxetine) and their metabolites in urine and plasma sam- ples using gas chromatography–mass spectrometry (GC– MS). The antidepressants were extracted with a Strata™ X solid-phase extraction (SPE) cartridge prior to analysis. The method presented linearity within the studied ranges in both samples with quantification limits varying from 1 to 15 ng mL -1 and determination coefficients (R 2 ) higher than 0.99 for all analytes in all runs. The limits of detec- tion ranged from 1 to 5 ng mL -1 for the compounds under study. The recovery for urine samples ranged from 40 to 89% and for plasma samples varied from 68 to 98%. Pre- cision and accuracy analysis showed acceptable coeffi- cients of variation and relative error, fulfilling the criteria normally accepted in bioanalytical method validation. The method developed proved to be suitable for screening of the studied drugs in urine and plasma samples, proving to be sensitive and presenting appropriate selectivity and sensi- tivity, allowing detection of small amounts of the analytes. * Eugenia Gallardo egallardo@fcsaude.ubi.pt 1 CICS-UBI, Centro de Investigação em Ciências da Saúde, Universidade da Beira Interior, Av. Infante D. Henrique, 6201-506 Covilhã, Portugal 2 CNC, Centro de Neurociências e Biologia Celular, Universidade de Coimbra, Rua Larga Faculdade de Medicina, Pólo I, 1º andar, 3004-504 Coimbra, Portugal 3 Departamento de Psiquiatria e Saúde Mental, Centro Hospitalar Cova da Beira, E.P.E., 6201-551 Covilhã, Portugal