Simultaneous determination of human plasma levels of citalopram, paroxetine, sertraline, and their metabolites by gas chromatography-mass spectrometry

Central composite design-assisted visual and non-invasive detection of sertraline by sweet lemon waste-derived core-shell AuNPs@CDs

This study reports a fast and visual detection method of antidepressant sertraline (SRT) drug by the core-shell AuNPs@CDs as the nanoprobes. The CDs has been eco-friendly synthesized from sweet lemon wastes to directly reduce Au+ to AuNPs without any external photoirradiation process or additional reductants. Optimizing key variables that impact the sensing process has been done using the central composite design (CCD) approach to simulate the assay condition before the analysis. Adding SRT with different concentrations to the nanoprobes under mildly acidic conditions presents an absorbance peak at 560 nm with purple color tonalities that differ from the behavior of alone nanoprobes (530 nm, pink color). The obtained absorption change is linearly proportional to the increase of SRT concentration from 1 μM to 35 μM with a limit of detection (LOD) value of 100 nM. The color changes with a vivid tonality from pink and purple to violet as the colorful fingerprint patterns are readily traceable by the naked eye, allowing the visual assay of SRT. The greenness of the developed approach is well evaluated by some international indexes including the complimentary green analytical procedure (ComplexGAPI) and also, the analytical greenness (AGREE) indexes. The proposed waste-derived nanoprobes based on the eco-friendly procedure not only conduct quantitative and qualitative non-invasive analysis of SRT by the naked eye but also, may widen for other applications in various fields.

[Ways to solve the problem of cross-reactions during immunochromatographic examination of biological objects]

The purpose of this review is to study the causes of cross-reactions of a number of drugs (mebeverine, phenibut, tropicamide, ramipril, metoprolol, phenylephrine, sertraline, chloropyramine and diphenhydramine) during the preliminary stage of laboratory diagnostics by immunochromatographic method and to propose a possible algorithm for solving this problem. Conducting a hair study in order to identify the fact of the use of psychoactive substances will increase the reliability of analytical diagnostics and reduce the likelihood of false positive results of the analysis. The use of a validated method of enzymatic hydrolysis of hair will eliminate unreliable results of the analysis due to the detection of the native molecule of the toxicant, increase the efficiency and accuracy of the diagnostic procedure.

Effect of Selected Antidepressants on Placental Homeostasis of Serotonin: Maternal and Fetal Perspectives

Depression is a prevalent condition affecting up to 20% of pregnant women. Hence, more than 10% are prescribed antidepressant drugs, mainly serotonin reuptake inhibitors (SSRIs) and selective serotonin and noradrenaline reuptake inhibitors (SNRIs). We hypothesize that antidepressants disturb serotonin homeostasis in the fetoplacental unit by inhibiting serotonin transporter (SERT) and organic cation transporter 3 (OCT3) in the maternal- and fetal-facing placental membranes, respectively. Paroxetine, citalopram, fluoxetine, fluvoxamine, sertraline, and venlafaxine were tested in situ (rat term placenta perfusion) and ex vivo (uptake studies in membrane vesicles isolated from healthy human term placenta). All tested antidepressants significantly inhibited SERT- and OCT3-mediated serotonin uptake in a dose-dependent manner. Calculated half-maximal inhibitory concentrations (IC₅₀) were in the range of therapeutic plasma concentrations. Using in vitro and in situ models, we further showed that the placental efflux transporters did not compromise mother-to-fetus transport of antidepressants. Collectively, we suggest that antidepressants have the potential to affect serotonin levels in the placenta or fetus when administered at therapeutic doses. Interestingly, the effect of antidepressants on serotonin homeostasis in rat placenta was sex dependent. As accurate fetal programming requires optimal serotonin levels in the fetoplacental unit throughout gestation, inhibition of SERT-/OCT3-mediated serotonin uptake may help explain the poor outcomes of antidepressant use in pregnancy.

Quantitation of escitalopram and its metabolites by liquid chromatography-tandem mass spectrometry in psychiatric patients: New metabolic ratio establishment

Therapeutic drug monitoring (TDM) is used to determine the concentration of drug in plasma/serum to adjust the dose of the therapeutic drug. Selective and sensitive analytical methods are used to determine drug and metabolite levels for the successful application of TDM. The aim of the study was to develop and validate using LC-MS/MS to analyse quantitative assay of escitalopram (S-CT) and metabolites in human plasma samples. In order to provide a convenient and safe treatment dose, it was aimed to determine the levels of S-CT and its metabolites in the patients' plasma. A new method with short sample preparation and analysis time was developed and validated using LC-MS/MS to analyse quantitative assay of S-CT and its metabolites in plasma. Also, plasma samples of 30 patients using 20 mg S-CT between the ages of 18 and 65 years were analysed by the validated method. The mean values of S-CT, demethyl escitalopram and didemethyl escitalopram in plasma of patients were 27.59, 85.52 and 44.30 ng/mL, respectively. At the end of the analysis, the metabolic ratio of S-CT and metabolites was calculated. It is considered that the method for the quantitative analysis of S-CT and its metabolites in human plasma samples may contribute to the literature on account of its sensitive and easy application. Additionally, the use of our data by physicians will contribute to the effective drug treatment for their patients who take S-CT.

A fast, sensitive and simple method for mirtazapine quantification in human plasma by HPLC-ESI-MS/MS. Application to a comparative bioavailability study

In the present study a simple, fast, sensitive and robust method to quantify mirtazapine in human plasma using quetiapine as the internal standard (IS) is described. The analyte and the IS were extracted from human plasma by a simple protein precipitation with methanol and were analyzed by high-performance liquid chromatography coupled to an electrospray tandem triple quadrupole mass spectrometer (HPLC-ESI-MS/MS). Chromatography was performed isocratically on a C(18), 5 µm analytical column and the run time was 1.8 min. The lower limit of quantitation was 0.5 ng/mL and a linear calibration curve over the range 0.5-150 ng/mL was obtained, showing acceptable accuracy and precision. This analytical method was applied in a relative bioavailability study in order to compare a test mirtazapine 30 mg single-dose formulation vs a reference formulation in 31 volunteers of both sexes. The study was conducted in an open randomized two-period crossover design and with a 14 day washout period. Since the 90% confidence interval for C(max) , AUC(last) and AUC(0-inf) were within the 80-125% interval proposed by the Food and Drug Administration and ANVISA (Brazilian Health Surveillance Agency), it was concluded that mirtazapine 30 mg/dose is bioequivalent to the reference formulation, according to both the rate and extent of absorption.

A fully validated method for the simultaneous determination of 11 antidepressant drugs in whole blood by gas chromatography-mass spectrometry

Antidepressant drugs are widely used for the treatment of depression and other psychiatric disorders and as a result they are involved in numerous clinical and forensic cases. The aim of this study was the development, optimization and validation of a simple, specific and sensitive GC/MS method for the simultaneous determination of 11 antidepressant drugs and 4 of their metabolites (amitriptyline, citalopram, clomipramine, fluoxetine, fluvoxamine, maprotiline, desmethyl-maprotiline, mirtazapine, desmethyl-mirtazapine, nortriptyline, paroxetine, sertraline, desmethyl-sertraline, venlafaxine and desmethyl-venlafaxine) in whole blood. The combination of solid-phase extraction with derivatization using heptafluorobutyric anhydride efficiently reduced matrix effect and improved sensitivity of the method. In this assay, protriptyline was used as internal standard. Absolute recovery values for all analytes were ranged from 79.2 to 102.6%. LODs and LOQs were found to be between 0.30-1.50 μg/L and 1.00-5.00 μg/L, respectively. The calibration curves were linear (R(2)≥0.990) within the range of 5.00-1000 μg/L for all analytes. Accuracy expressed as the % E(r) was found to be between -12.3 and 12.2%. Precision expressed as the % RSD was found to be less than 11.7% for all antidepressants. The developed method proved to be suitable for routine work and it was used to successfully analyze more than 2500 clinical and forensic blood samples.

Early telephone intervention for psychiatric outpatients starting antidepressant treatment

BACKGROUND

The article addresses the hypothesis that early telephone intervention for psychiatric outpatients starting antidepressant treatment would increase compliance with pharmacological treatment and retention time in the study, and thus allow for a more favourable clinical outcome.

METHODS

The study focuses on 131 depressed outpatients who participated in a study aiming to obtain full remission. Patients who benefited from three early structured telephone interventions (n=81) were compared with participants who benefited from the usual care (n=50) with no clinical contact before the first clinical assessment at 2 weeks.

RESULTS

The intervention proved to have no significant effect on treatment adherence, attrition rate, exclusion rate for adverse events or improvement of depression severity. It was nevertheless associated with increased retention time in the present study.

CONCLUSIONS

These results suggest that motivational phone calls may reinforce adhesion in psychiatric patients and provide early opportunities to adapt treatment to individual needs.

CLINICAL IMPLICATION

These results suggest that motivational phone calls may reinforce adhesion in psychiatric patients and provide early opportunities to adapt treatment to individual needs.

Effects of the serotonin 1A, 2A, 2C, 3A, and 3B and serotonin transporter gene polymorphisms on the occurrence of paroxetine discontinuation syndrome

Paroxetine discontinuation symptoms can at times be severe enough to reduce the quality of life. However, it is currently not possible to predict the occurrence of discontinuation syndrome before the initiation or discontinuation of paroxetine treatment. In this study, we investigated the effects of genetic polymorphisms in the serotonin 1A, 2A, 2C, 3A, and 3B receptor, the serotonin transporter, and the cytochrome P450 2D6 (CYP2D6) genes on the occurrence of paroxetine discontinuation syndrome. A consecutive series of 56 Japanese patients who had a diagnosis of major depressive or anxiety disorder according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, were treated with paroxetine. Paroxetine discontinuation syndrome was found in 35.7% of the patients by direct interview. Patients who stopped taking paroxetine abruptly experienced paroxetine discontinuation syndrome significantly more often than patients who had a tapering off of the dosage of medication. Patients who had the -1019C allele experienced paroxetine discontinuation syndrome more frequently than patients who had the -1019G homozygote (nominal P = 0.0423) of the serotonin 1A receptor gene. However, this result did not remain significant after the Bonferroni correction for multiple comparisons. The findings suggest that the abrupt stoppage of medication is a major risk factor for the occurrence of paroxetine discontinuation syndrome and that C(-1019)G polymorphism of the serotonin 1A receptor gene may be related to the occurrence of the syndrome.

Simple spectrophotometric method for determination of paroxetine in tablets using 1,2-naphthoquinone-4-sulphonate as a chromogenic reagent

Simple and rapid spectrophotometric method has been developed and validated for the determination of paroxetine (PRX) in tablets. The proposed method was based on nucleophilic substitution reaction of PRX with 1,2-naphthoquinone-4-sulphonate (NQS) in an alkaline medium to form an orange-colored product of maximum absorption peak (λ_max) at 488 nm. The stoichiometry and kinetics of the reaction were studied, and the reaction mechanism was postulated. Under the optimized reaction conditions, Beer's law correlating the absorbance (A) with PRX concentration (C) was obeyed in the range of 1–8 μg mL⁻¹. The regression equation for the calibration data was: A = 0.0031 + 0.1609 C, with good correlation coefficients (0.9992). The molar absorptivity (ε) was 5.9 × 10⁵ L mol⁻¹ 1 cm⁻¹. The limits of detection and quantitation were 0.3 and 0.8 μg mL⁻¹, respectively. The precision of the method was satisfactory; the values of relative standard deviations did not exceed 2%. The proposed method was successfully applied to the determination of PRX in its pharmaceutical tablets with good accuracy and precisions; the label claim percentage was 97.17 ± 1.06 %. The results obtained by the proposed method were comparable with those obtained by the official method.

CYP2D6 and ABCB1 genetic variability: influence on paroxetine plasma level and therapeutic response

Paroxetine is characterized by large interindividual pharmacokinetic variability and heterogeneous response patterns. The present study investigates plasma concentration and therapeutic response to paroxetine for the influence of age, sex, and CYP2D6 and ABCB1 polymorphisms, the latter gene encoding for the permeability glycoprotein. Genotyping for CYP2D6 (alleles *3, *4, *5, *6, and *xN) and ABCB1 polymorphisms (61A>G, 2677G>T, and 3435C>T) was performed in 71 depressed patients who started 20 mg paroxetine per day and had plasma concentration measured after 2 weeks at a fixed dose. A dose increase to 30 mg per day was possible starting at week 2. For 63 patients, severity of depression (Montgomery-Asberg Depression Rating Scale) was assessed at weeks 0, 2, and 4 and every 2 weeks thereafter until discontinuation. Persistent response was defined as 50% improvement from baseline score sustained from the first occurrence to study end point. Paroxetine concentration significantly differed between female and male patients (median, 28 versus 16 ng/mL; P = 0.001). Differences were not significant between CYP2D6 heterozygous and homozygous extensive metabolizers (median, 27 versus 22 ng/mL; P = 0.074) and between ABCB1 genotypes (P > 0.10). When considered in a multivariate model, CYP2D6 heterozygous extensive metabolizer phenotype (P = 0.062) and female gender (P = 0.001) predicted 1.3-fold and 1.6-fold higher paroxetine concentration, respectively, but fraction of explained variability was modest (21%). Frequency of persistent response at study end point did not significantly differ according to CYP2D6 heterozygous extensive metabolizer versus homozygous extensive metabolizer phenotype and ABCB1 polymorphisms in univariate analyses. After adjusting for age, sex, paroxetine concentration at week 2, and daily dose at study end point, ABCB1 genotype contributed to improving the model significantly for 61A>G (P = 0.043), but not 2677G>T (P = 0.068) and 3435C>T (P = 0.11). None of two poor metabolizers and four ultrarapid metabolizers showed persistent response to paroxetine. The hypothesis that permeability glycoprotein activity might be a relevant predictor of therapeutic response deserves to be further investigated while controlling for pharmacokinetic variability.

New spectrofluorimetric method with enhanced sensitivity for determination of paroxetine in dosage forms and plasma

New simple spectrofluorimetric method with enhanced sensitivity has been developed and validated for the determination of the antidepressant paroxetine (PXT) in its dosage forms and plasma. The method was based on nucleophilic substitution reaction of PXT with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole in an alkaline medium (pH 8) to form a highly fluorescent derivative that was measured at 545 nm after excitation at 490 nm. The factors affecting the reaction was carefully studied and optimized. The kinetics of the reaction was investigated, and the reaction mechanism was presented. Under the optimized conditions, linear relationship with good correlation coefficient (0.9993) was found between the fluorescence intensity and PXT concentration in the range of 80-800 ng ml(-1). The limits of detection and quantitation for the method were 25 and 77 ng ml(-1), respectively. The precision of the method was satisfactory; the values of relative standard deviations did not exceed 3%. The proposed method was successfully applied to the determination of PXT in its pharmaceutical tablets with good accuracy; the recovery values were 100.2 +/- 1.61%. The results obtained by the proposed method were comparable with those obtained by the official method. The proposed method is superior to the previously reported spectrofluorimetric method for determination of PXT in terms of its higher sensitivity and wider linear range. The high sensitivity of the method allowed its successful application to the analysis of PXT in spiked human plasma. The proposed method is practical and valuable for its routine application in quality control and clinical laboratories for analysis of PXT.

Genetic polymorphisms in the 5-hydroxytryptamine type 3B receptor gene and paroxetine-induced nausea

Selective serotonin reuptake inhibitor (SSRI)-induced nausea can be severe enough to lead to early treatment discontinuation. However, it is currently not possible to predict the occurrence of nausea before the initiation of SSRI treatment. In this study, we investigated the effect of genetic polymorphisms in the 5-hydroxytryptamine type 2A, 3A, and 3B (5-HT3B) receptors, 5-HT transporter, and CYP2D6 genes on the incidence of paroxetine-induced nausea. A consecutive series of 72 Japanese patients with depressive or anxiety disorders were treated with paroxetine. Paroxetine-induced nausea was assessed by a pharmacist and was observed in 29.2% of the patients. A significant (nominal p=0.00286) association was found between the incidence of nausea and the -100_-102AAG insertion/deletion polymorphism of the 5-HT3B receptor gene. No significant associations were observed between the other genetic polymorphisms and the incidence of nausea. The -100_-102AAG deletion variant of the 5-HT3B receptor gene may affect paroxetine-induced nausea.

Comparison of electron and chemical ionization modes by validation of a quantitative gas chromatographic-mass spectrometric assay of new generation antidepressants and their active metabolites in plasma

A gas chromatographic-mass spectrometric method (GC-MS) for the simultaneous determination of the 'new' antidepressants (mirtazapine, viloxazine, venlafaxine, trazodone, citalopram, mianserin, reboxetine, fluoxetine, fluvoxamine, sertraline, maprotiline, melitracen, paroxetine) and their active metabolites (desmethylmirtazapine, O-desmethylvenlafaxine, m-chlorophenylpiperazine, desmethylcitalopram, didesmethylcitalopram, desmethylmianserin, desmethylfluoxetine, desmethylsertraline, desmethylmaprotiline) in plasma using different ionization modes was developed and validated. Sample preparation consisted of a strong cation exchange mechanism and derivatisation with heptafluorobutyrylimidazole. The GC separation was performed in 24.8 min. Identification and quantification were based on selected ion monitoring in electron (EI) and chemical ionization (CI) modes. Calibration by linear and quadratic regression for electron and chemical ionization, respectively, utilized deuterated internal standards and a weighing factor 1/x(2). Limits of quantitation were established between 5 and 12.5 ng/ml in EI and positive ionization CI (PICI), and 1 and 6.25 ng/ml in negative ionization CI (NICI). During validation stability, sensitivity, precision, accuracy, recovery, and selectivity were evaluated for each ionization mode and were demonstrated to be acceptable for most compounds. While it is clear that not all compounds can be quantitated either due to chromatographic (trazodone) or derivatisation problems (O-desmethylvenlafaxine), this method can quantitate most new antidepressants (ADs) in the therapeutic range using EI. PICI and NICI lead to higher selectivity. Moreover, NICI is of interest for small sample volumes and high sensitivity requirements. This paper draws the attention to the pros and cons of the different ionization modes in the GC-MS analysis of these antidepressants in plasma.

Reliable HPLC method for therapeutic drug monitoring of frequently prescribed tricyclic and nontricyclic antidepressants

A new high-performance liquid chromatography method is presented for the determination of 10 frequently prescribed tricyclic and nontricyclic antidepressants: imipramine, amitriptyline, clomipramine, fluoxetine, sertraline, paroxetine, citalopram, mirtazapine, moclobemide and duloxetine. The simple and accurate sample preparation step, consisted of liquid:liquid extraction with recoveries ranging between 72% and 86%, except for moclobemide (59%). Separation was obtained using a reverse phase Select B column under isocratic conditions with UV detection (230 nm). The mobile phase consisted of 35% of a mixture of acetonitrile/methanol (92:8, v/v) and 65% of 0.25 mol L(-1) sodium acetate buffer, pH 4.5. The standard curves were linear over a working range of 2.5-1000 ng mL(-1) for moclobemide, 5-2000 ng mL(-1) for citalopram, duloxetine, fluoxetine, 10-2000 ng mL(-1) for sertraline, imipramine, paroxetine, mirtazapine and clomipramine. The intra-assay and inter-assay precision and accuracy were studied at three concentrations (50, 200, and 500 ng mL(-1)). The intra-assay coefficients of variation (CVs) for all compounds were less than 8.8%, and all inter-CVs were less than 10%. Limits of quantification were 2.5 ng mL(-1) for moclobemide, 5 ng mL(-1) for citalopram, duloxetine and amitriptyline, and 10 ng mL(-1) for mirtazapine, paroxetine, imipramine, fluoxetine, sertraline, and clomipramine. No interference of the drugs normally associated with antidepressants was observed. The method has been successfully applied to the analysis of real samples, for the drug monitoring of ten frequently prescribed tricyclic and non-tricyclic antidepressant drugs.

High-throughput on-line solid-phase extraction–liquid chromatography–tandem mass spectrometry method for the simultaneous analysis of 14 antidepressants and their metabolites in plasma

A rapid, sensitive and fully automated on-line solid-phase extraction-liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS) method was developed and validated for the direct analysis of 14 antidepressants and their metabolites in plasma. Integration of the sample extraction and LC separation into a single system permitted direct injection of the plasma without prior sample pre-treatment. The applied gradient ensured the elution of all the examined drugs within 14 min and produced chromatographic peaks of acceptable symmetry. The total process time was 20 min and only 50 microL of plasma was required. Selectivity of the method was achieved by a combination of retention time and two precursor-product ion transitions for the non-deuterated compounds. The use of SPE was demonstrated to be highly effective and led to significant decreases in the interferences present in the matrix. Extraction was found to be both reproducible and efficient with recoveries >99% for all the analytes. The method showed excellent intra-assay and inter-assay precision (relative standard deviation (RSD) and bias <20%) for quality control (QC) samples spiked at a concentration of 40, 200 and 800 microg/L and the r2>0.99 over the range investigated (10-1000 microg/L). Limits of quantification (LOQs) were estimated to be 10 microg/L. Furthermore, the processed samples were demonstrated to be stable for at least 48 h, except for clomipramine and norclomipramine, where a slight negative trend was observed, but did not compromise the quantification. The method was subsequently applied to authentic samples previously screened by a routine HPLC method with diode array detection (DAD).

Determination of sertraline andN-desmethylsertraline in human plasma by CE with LIF detection

A method has been developed for the analysis of the antidepressant drug sertraline together with its main metabolite N-desmethylsertraline (DMS) in human plasma. It is based on CE with LIF detection (lambda = 488 nm). A SPE procedure is employed for biological sample pretreatment, followed by a derivatization step with FITC; reboxetine was the internal standard. The effect of CD, acetone and N-methyl-D-glucamine (GLC) as constituents of the BGE for analyte separation was investigated. The final BGE consisted of 20 mM carbonate buffer, pH 9.0, with 2.5 mM heptakis(2,6-di-O-methyl)-beta-CD, 50 mM GLC and 20% v/v acetone. With 30 kV applied voltage, the electrophoretic run is completed in 7.5 min. Linearity was observed in the plasma concentration range from 3.0 to 500 ng/mL for sertraline and 4.0 to 500 ng/mL for DMS. Extraction yield was >97.1%, precision - expressed as RSD% - was <3.7, accuracy (recovery) was >95.6%. Due to its sensitivity and selectivity, the method was suited for the analysis of plasma samples from patients undergoing therapy with sertraline.

Time course of response to paroxetine: influence of plasma level

Early improvement of depression severity is considered an important therapeutic goal, predictive of later remission. The present study aimed at testing the hypothesis that plasma concentration might influence the time course of response to paroxetine. Eighty-four patients with a severe depressive episode started paroxetine 20 mg/day, with a possible dose adjustment to 30 mg/day after 2 weeks. Severity of depression (Montgomery-Asberg Depression Rating Scale) was assessed at weeks 0, 2 and 4 for all patients, and every 2 weeks thereafter until discontinuation. Median duration on paroxetine was 6 weeks (range 4-18 weeks). Plasma concentration was measured at steady-state after 2 weeks at 20 mg/day. In a first stage, pattern analysis led to distinguish patients with non-response, non-persistent response, early persistent response (obtained at week 2) and delayed persistent response (week 4 or later). Comparison of patients with (n=29, 34.5%) and without persistent response (n=55, 65.5%) did not reveal any significant difference, whereas focus on patients with persistent response indicated that shorter time to response was significantly associated with shorter duration of current episode (r(S)=0.54, p=0.003) and higher plasma level (r(S)=-0.47, p=0.011). In a second stage, a sigmoid mixed effects model was developed that adequately fitted depression severity versus time profiles among patients with persistent response (n=157 data for 29 patients). Estimated median time to response was 3.2 weeks (range 0.9-6.6). Higher paroxetine concentration, younger age and shorter episode duration were confirmed as significant determinants of a shorter time to response (likelihood ratio tests, p<0.005). The present study supports the hypothesis that higher paroxetine concentration might contribute to hasten relief of depressive symptoms in severely depressed patients.

Determination of the antidepressant paroxetine and its three main metabolites in human plasma by liquid chromatography with fluorescence detection

A high-performance liquid chromatographic method has been developed for the determination in human plasma of the specific serotonin reuptake inhibitor (SSRI) antidepressant paroxetine and its three main metabolites (M1, M2, M3). Fluorescence detection was used, exciting at lambda = 294 nm and monitoring emission at lambda = 330 nm for paroxetine (lambda(exc) = 280 nm, lambda(em) = 330 nm for M1 and M2; lambda(exc) = 268 nm, lambda(em) = 290 nm for M3). Separation was obtained on a reversed-phase C18 column using a mobile phase composed of 66.7% aqueous phosphate at pH 2.5 and 33.3% acetonitrile. Imipramine (lambda(exc) = 252 nm, lambda(em) = 390 nm) was used as the internal standard. A careful pre-treatment of plasma samples was developed, using solid-phase extraction with C8 cartridges (50 mg, 1 mL). The calibration curves were linear over a working range of 2.5-100 ng mL(-1) for paroxetine and of 5-100 ng mL(-1) for all metabolites. The limit of detection (LOD) was 1.2 ng mL(-1) for PRX and 2.0 ng mL(-1) for the metabolites. The method was applied with success to plasma samples from depressed patients undergoing treatment with paroxetine. Hence, the method seems to be suitable for the therapeutic drug monitoring of paroxetine and its main metabolites in depressed patients' plasma.

Screening of citalopram, fluoxetine and their metabolites in human urine samples by gas chromatography–mass spectrometry

Capillary gas chromatography with mass spectrometry detection in SIM mode (GC-MS-SIM) has been used for the analysis of citalopram (CIT), fluoxetine (FLX), and all of their metabolites in urine samples. The instrumental parameters affecting GC separation and MS-SIM detection were investigated. A validation procedure was performed on urine matrix and a simultaneous robustness/ruggedness evaluation is also presented in this paper. An optimized solid-phase extraction (SPE) has been applied, reaching in this way to limits of detection (LODs) between 0.7 ng L(-1) (CIT) and 33.6 microg L(-1) (CIT-PA). A pharmacokinetic screening in clinical urine samples has been also carried out.

Determination of Paroxetine in Human Plasma by High-Performance Liquid Chromatography Using 7,7,8,8-Tetracyanoquinodimethane as the Derivatization Reagent

A selective and sensitive reversed-phase HPLC method was developed for the determination of the antidepressant paroxetine in plasma. The method is based on the purple chromogen formed by a displacement reaction of paroxetine with 7,7,8,8-tetracyanoquinodimethane (TCNQ) in acetonitrile at 80 degrees C for 20 minutes. For the assay, the drug was extracted from 1 mL of plasma with chloroform and, after sample alkalinization, derivatized with TCNQ; then the reaction mixture was directly injected into a C18 column. Desipramine was used as internal standard. The mobile phase was acetonitrile-water (70:30) at a flow-rate of 1.0 mL/min, and the derivatives were eluted at 13.1 and 15.5 minutes for paroxetine and desipramine, respectively, and detected at 567 nm. Calibration curve was found linear over the range of 20-400 ng/mL, and the detection limit was 2 ng/mL at a signal-to-noise ratio of 3/1. Recoveries determined for 3 concentrations range between 81.3% and 88.1%. Intraday and interday relative standard deviation values were found to be within 3.8%-13.5% and 8.2%-14.6%, respectively. With this developed method, a pharmacokinetic study was performed for paroxetine.

A Fully Automated Turbulent-Flow Liquid Chromatography-Tandem Mass Spectrometry Technique for Monitoring Antidepressants in Human Serum

Antidepressants belong to a variety of chemical and pharmacologic classes. Most require therapeutic drug monitoring, at least in certain circumstances, such as unexplained inefficacy or suspected toxicity. Several types of chromatographic methods have generally been used. This paper presents a fully automated, sensitive, and specific method for the therapeutic drug monitoring of 13 antidepressants of all classes (amoxapine, amitriptyline, citalopram, clomipramine, dothiepin, doxepin, fluoxetine, imipramine, maprotiline, mianserin, paroxetine, sertraline, trimipramine) and some of their respective active metabolites (nortriptyline, monodesmethylcitalopram, desmethylclomipramine, desipramine, norfluoxetine, desmethylmianserin, N-desmethylsertraline), based on the innovative turbulent-flow liquid chromatography (TFC) technology, coupled to tandem-mass spectrometry (MS/MS). The antidepressants were divided in two groups depending on their chromatographic properties, so that two injections would be necessary to screen all compounds (which is infrequent for therapeutic drug monitoring). Calibration curves ranged from 10 to 500 ng/mL. No significant memory effect was observed after the injection of a blank serum sample spiked at 500 ng/mL. The intra-assay and inter-assay precision CVs ranged from 0.4% to 12% and from 1% to 16%, respectively. The method was further validated by blindly analyzing Heathcontrol-Therapeutic Drugs Scheme samples (Cardiff Bioanalytical Services Ltd.) containing several antidepressants.

Development and validation of a liquid chromatographic/tandem mass spectrometric method for the determination of sertraline in human plasma

A sensitive and rapid liquid chromatographic/tandem mass spectrometric method was developed and validated for the determination of sertraline in human plasma. The analyte and internal standard (IS, diphenhydramine) were extracted with 3 mL of diethyl ether/dichloromethane (2:1, v/v) from 0.25 mL plasma, then separated on a Zorbax Eclipse XDB C18 column using methanol/water/formic acid (75:25:0.1, v/v/v) as the mobile phase. The triple quadrupole mass spectrometry was applied via an atmospheric pressure chemical ionization (APCI) source for detection. The fragmentation pattern of the protonated sertraline was elucidated with the aid of product mass spectra of isotopologous peaks. Quantification was performed using selected reaction monitoring of the transitions of m/z 306 --> 159 for sertraline and m/z 256 --> 167 for the IS. The method was linear over the concentration range of 0.10-100 ng/mL. The intra-day and inter-day precisions, expressed by relative standard deviation, were both less than 6.7%. Assay accuracies were within +/-6.9% as terms of relative error. The lower limit of quantification (LLOQ) was identifiable and reproducible at 0.10 ng/mL with a precision of 8.3% and an accuracy of 9.6%. The validated method has been successfully applied for the pharmacokinetic study and bioequivalence evaluation of sertraline in 18 healthy volunteers after a single oral administration of 50 mg sertraline hydrochloride tablets.

The characterisation of selected antidepressant drugs using electrospray ionisation with ion trap mass spectrometry and with quadrupole time-of-flight mass spectrometry and their determination by high-performance liquid chromatography/electrospray ionisation tandem mass spectrometry

The electrospray ionisation ion trap tandem mass spectrometry (ESI-MS(n)) of selected antidepressant drugs, i.e., citalopram, fluoxetine, mirtazapine, paroxetine, sertraline, and venlafaxine, has been investigated. Sequential product ion fragmentation experiments (MS(n)) have been performed in order to elucidate the degradation pathways for the [M+H](+) ions and their predominant product ions. These MS(n) experiments show certain characteristic fragmentations in that functional groups are generally cleaved from the ring systems as molecules such as H(2)O, amines and phenols. When an aromatic entity is present in a drug molecule together with a nitrogen-containing saturated ring structure as with mirtazapine, fragmentation initially occurs at the latter ring with the former being predictably resistant to fragmentation. Also, when an amine-containing drug molecule such as fluoxetine also contains a functional group, which liberates a phenol with a significantly lower DeltaH(f) (0) value than that of the corresponding amine, the phenol is preferentially liberated. The structures of product ions proposed for ESI-MS(n) can be supported by electrospray ionisation quadrupole-time-of-flight tandem mass spectrometry (ESI-QToF-MS/MS). These molecules can be identified and determined in mixtures at low ng/mL concentrations by the application of high-performance liquid chromatography/electrospray ionisation tandem mass spectrometry (HPLC/ESI-MS(2)), which can also be used for their analysis in hair samples.

Sensitive capillary GC-MS-SIM determination of selective serotonin reuptake inhibitors: Reliability evaluation by validation and robustness study

A simple, fast, selective and very sensitive capillary GC-MS method for the simultaneous determination of five antidepressant drugs is described. Fluoxetine, fluvoxamine, citalopram, sertraline and paroxetine belong to the newest and most important drug group termed selective serotonin reuptake inhibitors. Imipramine was used in this method as an internal standard for quantification. Optimum parameters for GC separation were investigated, i.e., flow rate, column head pressure, injector temperature, injection splitless conditions and oven temperature program. MS detection was performed in SIM mode to increase the sensitivity. Stability of the solutions, linear concentration range, accuracy, precision, LOD, LOQ (3.6-41.5 mg/L) and specificity were examined in the presence of excipients for checking the reliability of this method. The robustness was evaluated with a matrix of 15 experiments (seven factors and three levels) using Plackett-Burman fractional factorial experimental design, and Youden and Steiner statistical treatment. The method was applied to the analysis of these antidepressants in nearly all their pharmaceutical formulations, obtaining recoveries between 98.1% and 102.7% with regard to the claimed values.

Spectrofluorimetric Determination of Paroxetine Hydrochloride in Its Formulations and Human Plasma

A sensitive spectrofluorimetric procedure for the determination of paroxetine-HCl in pharmaceutical formulations and human plasma has been described. The native fluorescence of the drug has been studied under different conditions. Maximum fluorescence intensity was obtained in methanol at 340 nm using 290 nm for excitation. Different surfactants showed negative effect on the fluorescence intensity of paroxetine-HCl. Regression analysis of Beer's plot showed good correlation (r=0.9999) between fluorescence intensity and concentration over the range of 0.05-0.40 microg ml-1 with lower limit of detection (LOD) of 0.015 microg ml-1. The drug was successfully determined in its tablets with average % recovery of 98.00+/-0.99% which was in accordance with those given by a compendial method. The method was also applied to the determination of paroxetine-HCl in spiked human plasma with average recovery of 77.70+/-1.06%.

Development of a solid phase extraction for 13 'new' generation antidepressants and their active metabolites for gas chromatographic-mass spectrometric analysis

A solid phase extraction procedure (SPE) for 13 'new' antidepressants (venlafaxine, fluoxetine, viloxazine, fluvoxamine, mianserin, mirtazapine, melitracen, reboxetine, citalopram, maprotiline, sertraline, paroxetine and trazodone) together with eight of their metabolites (O-desmethylvenlafaxine, norfluoxetine, desmethylmianserine, desmethylmirtazapine, desmethylcitalopram, didesmethylcitalopram, desmethylsertraline and m-chlorophenylpiperazine) from plasma is optimized using HPLC-DAD as monitoring system. Special attention has been paid to the choice of washing and eluting solvent, resulting in a highly concentrated, clean and moisture free extract, also suitable for GC-MS. A total number of 10 sorbents (apolar, polymeric, ion-exchange and mixed mode) was evaluated. Based on recovery, reproducibility and absence of interfering substances the strong cation exchanger gave the best results. Recoveries were determined at low and high therapeutic and toxic levels and ranged between 70 and 109% for all compounds, except for trazodone (39%).