Rev Anal Chem 30 (2011): 87–122 © 2011 by Walter de Gruyter • Berlin • Boston. DOI 10.1515/REVAC.2011.018 Analytical methods for determination of selective serotonin reuptake inhibitor antidepressants Z ü hre S¸ ent ü rk 1 , Cafer Saka 2, * and I˙ brahim Te gˇ in 3 depression is an inadequate amount of serotonin, by prevent- 1 Department of Chemistry , Faculty of Science and Letters, ing the reuptake of serotonin with the presynaptic neuron. Y ü z ü nc ü Y ı l University, Van , Turkey Serotonin plays a part in the treatment of various disorders 2 School of Health , S ı ı rt University, S ı ı rt , Turkey , such as anxiety, depression, schizophrenia, pain, hyperten- e-mail: [email protected] sion, vascular disorders, and migraine (Asberg et al. 1976 ). 3 Department of Chemistry , Faculty of Science and Letters, SSRIs specifi cally prevent the reuptake of serotonin by S ı ı rt University, S ı ı rt , Turkey increasing the level of active serotonin in synapses. They have varying degrees of selectivity for the other monoam- *Corresponding author ine transporters, with pure SSRIs having only weak affi nity for the noradrenaline and dopamine transporter. Therefore, determination of SSRI pharmaceutical or biological samples Abstract are very important in pharmacokinetic, in therapeutic drug monitoring, and in bioequivalence studies. For these reasons, Selective serotonin reuptake inhibitors (SSRIs) are commonly reliable analytical methods are needed which reliably deter- used to treat depression. SSRIs are classifi ed as fl uoxetine, mine plasma levels of SSRI drugs in order to detect changes paroxetine, escitalopram, citalopram, sertraline, and fl uvox- (either desired or otherwise) as early as possible in the plasma amine. Several methods have been published for the determi- concentrations of the drugs themselves. SSRI drugs have side nation of SSRI drugs in pharmaceuticals, biological materials effects including sexual dysfunction, gastrointestinal effects, and environmental samples. This review covers the analyti- and disruption of the central nervous system (Khawam et al. cal methods described in the literature for the determination 2006 , Barlow and Durand 2009 ). of SSRIs and their main metabolites or some compounds In recent years, advanced analytical methods have been belonging to the same SSRI group. The analytical methods developed and optimized in the fi eld of pharmaceutical anal- are generally chromatography based methods coupled to dif- ysis, with the aim of improving precision and sensitivity, in ferent detectors, electroanalytical methods, capillary zone order to accurately quantify trace concentrations of pharma- electrophoretic methods, and spectrometric methods. ceuticals present in pharmaceutical formulations and biologi- cal fl uids. Keywords: analytical methods; antidepressant; pharmaceu- In this article, a review of the analytical methods for the tical and biological samples; selective serotonin reuptake determination of SSRI drugs is presented. SSRIs are clas- inhibitors. sifi ed as fl uoxetine (FL), paroxetine (PXT), escitalopram (ESCIT), citalopram (CIT), sertraline (SER), and fl uvoxam- ine (FLU). Analytical methods described in the literature for Introduction the determination of SSRIs and its main metabolites or some compounds belonging to the same SSRI group are generally Depression is a chronic or recurrent mood disorder that chromatographic based methods coupled to different detec- affects both economic and social functions of approximately tors, electroanalytical methods, capillary zone electrophoretic 121 million people worldwide. According to the World methods, and spectrometric methods. Additionally, analytical Health Organization, depression will be the second lead- methods such as the immunoassay and titrimetry methods ing contributor to the global burden of disease. Depression have also been described in the literature for the determina- can lead to suicide. Analyses of the risks of taking selective tion of SSRIs. However, these methods are not covered in serotonin reuptake inhibitors (SSRIs) have resulted in warn- the review. Figure 1 shows the chemical structures of SSRI ings about suicidality and aggression when these medications drugs. are used with children and adolescents. The US Food and Drug Administration (FDA) indicated that there is a 1.5-fold increase of suicidality in the 18 – 24 age group. This resulted in Sample preparation a black box warning on SSRIs and other antidepressant medi- cations regarding the increased risk of suicidality in patients Several methods for sample preparation of SSRIs in phar- younger than 24 years (Levenson and Holland 2007 , Stone maceutical formulations and biological fl uids such as human and Jones 2007 , FDA 2008 , Wille et al. 2008 ). Antidepressants plasma, human urine samples, rat plasma, rat brain sam- are commonly used for the treatment of depression and obses- ples, fi sh tissue, hair samples, and human serum have been sive compulsive disorders. It is thought that one reason for described in the literature. The most common are liquid- 88 Z. S¸ ent ü rk et al.: Analytical methods for determination of SSRIs H N O NHCH3 O O O CF3 F Fluoxetine Paroxetine H CF NH 3 CH3 NH Cl N 2 O OCH3 H Cl Sertraline Fluxamine CN CH 3 H3C O N CH 3 N F H3C O F N Citalopram Escitalopram Figure 1 Chemical structures of SSRIs. liquid extraction (LLE) and solid phase extraction (SPE) with the multiple reaction monitoring (MRM) for the simultane- C18 and C8 columns. However, these methods present some ous determination of some drugs, including CIT, FL, FLU disadvantages and are laboriously time-consuming and use norfl uoxetine, and PXT in serum of 0.1 ml, which requires expensive solvents. Solid-phase microextraction (SPME), protein precipitation using acetonitrile/methanol. Acids such stir bar sorptive extraction (SBSE), protein precipitation and as trichloroacetic acid can also be used for protein precipita- direct injection of biological samples without sample prepa- tion prior to analysis of SSRI samples. Deproteinization using ration supported liquid membrane extraction (SLM), liquid- trichloroacetic acid 10 % (w/v) for the determination of FLU solid extraction (LSE), liquid phase microextraction (LPME), in plasma with recovery levels of 57.54 % has been reported pressurized liquid extraction (PLE) have also been employed (Fernandes et al. 2006 ). This method demonstrated the effec- for SSRI determination. These methods show some disadvan- tiveness of simple precipitation of proteinaceous material tages being laborious and time-consuming. using an organic solvent. Protein precipitation Liquid-liquid extraction (LLE) Protein precipitation is the simplest means of bioanalytical LLE has been exploited as an extraction procedure for SSRIs sample pretreatment. It only involves the addition of a pre- from complex matrices. In a method published on the deter- cipitating solvent, subsequent homogenizing and centrifu- mination of SSRIs, human plasma or serum samples were gation. Deproteinization is rarely used in the extraction of prepared using a three-step LLE (Ulrich 2003 ). Massaroti SSRIs from biological matrices. Reubsaet and Bjergaard et al. ( 2005 ) presented a high-performance liquid chroma- (2004) used a protein precipitation method for screening of tography coupled with tandem mass spectrometry (LC-MS/ more than 70 central nervous system-stimulating drugs in MS) method for PXT quantifi cation in human EDTA plasma human plasma, including CIT, PXT, and SER. Acetonitrile based on LLE using a mixture of ethyl acetate/hexane (50:50, was used to precipitate the proteins. Kirchherr and Kuhn - v/v) with retention times of 1.6 and 1.7 for PXT and FL, Velten (2006) developed another high-performance liquid respectively. Several papers have reported extraction with chromatography-mass spectrometry (HPLC-MS) method in acetonitrile methanol or prior to clean-up of the extracts by Z. S¸ ent ü rk et al.: Analytical methods for determination of SSRIs 89 LLE with hexane. In some cases, this procedure was followed 300 µ l human plasma by using a SPE procedure with mixed- by SPE. SLM extraction and/or enrichment for selective sepa- mode cation exchange cartridges. The SPE cartridges were ration and concentration of various metal ions from aqueous activated by passing 1 ml of methanol through the cartridge dilute solutions is similar to LLE. SLM uses the relatively three times, and then conditioned by passing 1 ml of a pH small volume of organic components in the membrane and 6.0, 25 m m phosphate buffer three times. CIT was used as simultaneous extraction and re-extraction. An automated the internal standard. Linearity ranged in the plasma over the sample pretreatment of human blood plasma for liquid chro- 5.0 – 160.0 ng/ml for each FLU isomer. Precision was better matographic determination of three antidepressant drugs than 4.0 % . (dibenzepine, reboxetine, fl uvoxamine), based on SLM for In recent years, much attention has been focused on the unsurpassed sample clean-up and analyte enrichment has development of on-line techniques. For such on-line sys- been developed by Barri and J onss ö n (2004) . The entire ana- tems, SPE is generally preferred over LLE as the isolation lytical procedure revealed good linearity and low detection technique, because it is less laborious, uses smaller amounts limits of 5, 15, and 20 ng/ml for dibenzepine, reboxetine, and of organic solvent, yields better analyte enrichment and is fl uvoxamine, respectively. easier to couple on-line to the chromatographic technique to be used. As compared to off-line SPE, on-line SPE offers Solid-phase extraction (SPE) a series of advantages such as analysis of the total amount of analytes extracted, small sample volumes are suffi cient SPE is a separation process that is dissolved or suspended in to obtain enough sensitivity, matrix effects, ionic suppres- a liquid mixture. SPE uses the affi nity of solutes dissolved or sion or enhancement in MS spectrometry, less fl exibility, suspended in a liquid for a solid through which the sample is and most systems do not allow the combined use of differ- passed to separate a mixture into desired and undesired com- ent cartridges, automatization and minimal sample handling ponents.