Development and characterization of a non-enzymatic electrochemical biosensor for rapid determination of sorbent-based extracted trazodone and doxepin in complicated samples.

BACKGROUND: Given the importance of achieving optimal therapeutical concentration in patients treated with antidepressants, this study investigates a novel technique for the simultaneous determination of trazodone (TRZ) and doxepin (DOX) in human plasma and serum samples for the first time. RESULTS: To achieve simultaneous determination of two antidepressants, TRZ and DOX, a novel detection system was designed: a non-enzymatic voltammetric biosensor based on boron-reduced graphene oxide/manganese oxide nanoparticles (GCE/B-rGO/MnO NPs). The detection was accomplished after pre-concentration and extraction trace amounts of the analytes using the thin film-solid phase microextraction (TF-SPME) technique, which employed polyvinyl alcohol/polyvinyl acetate/copper oxide nanoparticles (PVA/PVAc/CuO NPs) electrospun nanofibers. The successful preparation of composite nanofibers and modified electrodes was confirmed using the evaluation of field emission-scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDX). Also, the composite nanofibers were characterized with attenuated total reflectance-Fourier transform-infrared (ATR-FT-IR) and X-ray diffraction (XRD). In the solution of TRZ and DOX, under optimum experimental conditions, the linear dynamic ranges (LDRs) were 0.1-20.0 µmol L-1 and 0.5-27.0 µmol L-1, respectively. Also, the limit of detection (LOD) values of TRZ and DOX were 0.032 and 0.150 µmol L-1. SIGNIFICANCE: PVAc acts as a cross-linking agent for PVA, and their mixture is effective for sample preparation and pre-concentration of analytes in complex matrices. Also, adding CuO NPs to this polymeric mixture enhanced the adsorption efficiency. Taking advantage of the high surface area of MnO NPs and the high electrical conductivity of B-rGO, and considering the superiority of their simultaneous utilization, the constructed electrochemical biosensor is both cost-effective and rapid. It demonstrates excellent stability, repeatability, and sensitivity for the simultaneous determination of TRZ and DOX under optimal conditions. This biosensor, the first of its kind, is specifically designed for the simultaneous determination of TRZ and DOX in human plasma and serum samples, representing a significant advancement in biosensing technology.

Polyoxomolybdate368 /polyaniline nanocomposite as a novel fiber for solid-phase microextraction of antidepressant drugs in biological samples.

A novel solid-phase microextraction fiber was synthesized by coating a stainless steel wire with polyoxomolybdate368 /polyaniline as a sorbent aimed at extraction of amitriptyline, nortriptyline, and doxepin as antidepressant drugs from urine and blood samples. The polyoxomolybdate368 /polyaniline composite coating was applied using electropolymerization process under constant potential. This composition leads to enhanced extraction efficiency of the fiber. Scanning electron microscopy images show that huge three-dimensional structures of polyoxomolybdate368 in composite induced more non-smooth and porous fiber. In order to optimize of the extraction process, a series of variables including concentration of the composite materials, coating thickness, pH, extraction time, salt addition, and stirring rate was investigated and optimum conditions were determined. Analysis of surface morphology and chemical composition was performed. High-performance liquid chromatography was used for separation and evaluation of mentioned antidepressant drugs from the matrixes. The experiments indicated a detection limits of <0.2 ng/L and a linear dynamic range of 0.3-100 ng/L (R2  > 0.994). The relative recovery values were found to be in the range of 92-98%. It was concluded that the purposed fiber is highly efficient in analyzing traces of antidepressant drugs in urine and blood.

High-throughput protein precipitation method with 96-well plate for determination of doxepin and nordoxepin in human plasma using LC-MS/MS.

The aim of this study was to establish a high-throughput and sensitive LC-MS/MS method for the determination of doxepin and its major active metabolite nordoxepin in human plasma. It has been designed for bioequivalence study for formulations containing 25 mg of doxepin. Doxepin and nordoxepin were extracted from human plasma samples by protein precipitation with acetonitrile by using protein precipitation 96-well plates. The analyte was separated using a Phenomenex Kinetex Biphenyl column (100 × 2.1 mm, 2.6 µm) using isocratic elution with a mobile phase of 20 mM ammonium formate (30%) and acetonitrile:methanol 3:7 v:v (70%) at a flow rate of 0.5 mL/min and an injection volume of 10 µL. The detection was performed using a triple quadrupole mass spectrometer by multiple reaction monitoring mode to monitor the precursor-to-product ion transitions of m/z 280.4 → 107.0 and 283.4 → 235.0 for doxepin and doxepin-D3, respectively, and 266.3 → 106.9 and 269.3 → 235.0 for nordoxepin and nordoxepin-D3, respectively, in positive electrospray ionization mode. The total run time was 3.5 min. The method was validated over a concentration range of 50-10,000 pg/mL using a Triple Quad 4500 MS System (Sciex) for both analytes. The developed and validated method can be successfully used to study the bioequivalence/pharmacokinetics of doxepin and nordoxepin.

Nortriptyline serum concentration as a predictor for cardiac risk in amitriptyline-treated patients.

PURPOSE: Tricyclic antidepressants have been shown to affect electrocardiogram (ECG) parameters, but there is limited evidence in relation to the serum concentrations. Therefore, we aimed to evaluate a prediction of cardiac risk in amitriptyline- and doxepin-treated patients by serum concentrations. PATIENTS AND METHODS: The association between serum concentrations of amitriptyline (n = 100) and doxepin (n = 71) and ECG parameters was retrospectively examined using linear regression analysis. Mann-Whitney U tests were applied to evaluate differences in QTc intervals in patients with serum concentrations above and below the upper limit of the therapeutic reference range, as well as the alert level of each target drug. RESULTS: The sum serum concentration of amitriptyline and the nortriptyline serum concentration were significantly associated with an increased PQ interval (p = 0.020, p = 0.007), as well as with increased QTcB (p = 0.012, p < 0.001) and QTcF intervals (p = 0.025, p < 0.001). The nortriptyline concentration was significantly associated with the QRS interval (p = 0.003). In patients with active moiety concentrations above the alert level (300 ng/ml) and nortriptyline concentrations above the reference range (170 ng/ml), the QTcB interval was significantly prolonged (p = 0.032, p = 0.007). No significant association with any ECG parameter was detected for doxepin serum concentrations. CONCLUSION: The effect of amitriptyline on ECG parameters may be explained by nortriptyline alone. Accordingly, with increasing nortriptyline concentrations, the potential risk for an atrioventricular block, a bundle branch block, and prolongation of QTc interval may increase significantly.

Construction of molecularly imprinted nanoparticles by employing ultrasound waves for selective determination of doxepin from human plasma samples: Modeling and optimization.

In this work, molecularly imprinted nanoparticles (MINPs) were applied as selective adsorbent for ultrasound-assisted micro-solid-phase extraction (UAMSPE) of doxepin (DP) from human plasma samples, which was then cleaned up, pre-concentrated and subjected to HPLC. The MINPs were synthesized based on a non-covalent approach by precipitation polymerization utilizing methacrylic acid and styrene as functional monomers, DP as template, ethylene glycol dimethacrylate as cross-linker and 2,2-azobisisobutyronitrile (AIBN) as initiator. The obtained MINPs were characterized by Fourier transform-infrared and field emission scanning electron microscopy. Factors influencing the efficiency of UAMSPE such as sonication time, volume of eluent solvent and amount of sorbent were investigated using a central composite design and the optimal points were identified as 4 min of sonication time, 380 µL of eluent solvent and 30 mg of sorbent. Under optimized conditions, the proposed method has linear responses in the range of 0.2-2000 ng mL-1 , with a satisfactory limit of detection of 0.04 ng mL-1 and limit of quantification of 0.11 ng mL-1 .

Analysis of smoking behavior on the pharmacokinetics of antidepressants and antipsychotics: evidence for the role of alternative pathways apart from CYP1A2.

Smoking is common among psychiatric patients and has been shown to accelerate the metabolism of different drugs. We aimed to determine the effect of smoking on the serum concentrations of psychopharmacological drugs in a naturalistic clinical setting. Dose-corrected, steady-state serum concentrations of individual patients were analyzed retrospectively by linear regression including age, sex, and smoking for amitriptyline (n=503), doxepin (n=198), mirtazapine (n=572), venlafaxine (n=534), clozapine (n=106), quetiapine (n=182), and risperidone (n=136). Serum levels of amitriptyline (P=0.038), clozapine (P=0.02), and mirtazapine (P=0.002) were significantly lower in smokers compared with nonsmokers after correction for age and sex. In addition, the ratios of nortriptyline/amitriptyline (P=0.001) and nordoxepin/doxepin (P=0.014) were significantly higher in smokers compared with nonsmokers. Smoking may not only induce CYP1A2, but may possibly also affect CYP2C19. Furthermore, CYP3A4, UGT1A3, and UGT1A4 might be induced by tobacco smoke. Hence, a different dosing strategy is required among smoking and nonsmoking patients. Nevertheless, the clinical relevance of the results remained unclear.

Antidepressant polypharmacy and the potential of pharmacokinetic interactions: Doxepin but not mirtazapine causes clinically relevant changes in venlafaxine metabolism.

BACKGROUND: To uncover pharmacokinetic interactions between venlafaxine and doxepin or mirtazapine in a naturalistic sample. METHODS: A therapeutic drug monitoring database containing plasma concentrations of venlafaxine (VEN) and its active metabolite O-desmethylvenlafaxine (ODVEN) was analyzed. We included 1067 of 1594 patients in the analysis. Three study groups were considered; a group of patients under venlafaxine without confounding medications, V0 (n = 905), a group of patients co-medicated with doxepin, VDOX (n = 25) and a second group, co-medicated with mirtazapine, VMIR, n = 137. Plasma concentrations of VEN, ODVEN and the clinically relevant active moiety, sum of venlafaxine and O-desmethylvenlafaxine (ODVEN) (AM), as well as dose-adjusted plasma concentrations (C/D) were compared. RESULTS: Median concentrations in the doxepin group showed 57.7% and 194.4% higher values for AM and VEN respectively; these differences were statistically significant (p < 0.001 for AM and p = 0.002 for VEN). Similar differences were detected for C/D concentrations of active moiety and VEN (p < 0.001 and p = 0.001) with higher values also in the doxepin group. The ratios ODVEN/VEN were lower in the doxepin group (p < 0.001). A co-medication with mirtazapine did not cause any changes in venlafaxine metabolism. CONCLUSIONS: Higher concentrations for VEN and AM imply an inhibiting effect of doxepin on the metabolism of venlafaxine, although the huge variability of concentrations has to be taken into account. It is recommended to monitor plasma concentrations in combination treatment to avoid problems in safety and efficacy. LIMITATIONS: Despite the large size of our study sample, the naturalistic nature of this data may arise some concerns of information bias potentially resulting from non-standardized data recording.

Polythiophene/graphene oxide nanostructured electrodeposited coating for on-line electrochemically controlled in-tube solid-phase microextraction.

In this work, a novel polythiophene/graphene oxide (PTh/GO) nanostructured coating was introduced for on-line electrochemically-controlled in-tube solid phase microextraction of amitriptyline (AMI) and doxepin (DOX) as antidepressant drugs. The PTh/GO coating was prepared on the inner surface of a stainless steel tube by a facile in-situ electro-deposition method and it was used as a working electrode for electrochemically control in-tube solid phase microextraction. In the PTh/GO coating, GO acts as an anion dopant and sorbent. The PTh/GO coating, compared to PTh and GO coatings, exhibited enhanced long lifetime, good mechanical stability and a large specific surface area. Regarding the in-tube SPME, some important factors such as the extraction and desorption voltage, extraction and desorption times and flow rates of the sample solution and eluent, which could affect the extraction and separation efficiency of the analytes, were optimized. Total analysis time of this method including the online extraction and desorption time was about 21min for each sample. AMI and DOX were extracted, separated and determined with limits of detection as small as 0.3µgL-1 and 0.5µgL-1, respectively. This method showed good linearity in the range of 0.7-200µgL-1, 2.3-200µgL-1 and 2.9-200µgL-1 for AMI, and in the range 0.9-200µgL-1, 2.5-200µgL-1 and 3.0-200µgL-1 for DOX in water, urine and plasma samples, respectively; the coefficients of determination were also equal to or higher than 0.9976. The inter- and intra-assay precisions (RSD%, n=3) were in the range of 2.8-3.4% and 2.9-3.9% at the three concentration levels of 5, 25 and 50µgL-1, respectively. Finally, under the optimal conditions, the method was applied for the analysis of the drugs in human urine and plasma pretreated samples and good results were obtained.

Electromembrane surrounded solid phase microextraction: a novel approach for efficient extraction from complicated matrices.

In the present work, electromembrane surrounded solid phase microextraction (EM-SPME) is introduced for the first time. The organic liquid membrane, which consists of 2-nitrophenyl octyl ether (NPOE), was immobilized in the pores of a hollow fiber (HF) and the basic analytes migrated in an electrical field from aqueous sample solution through the liquid membrane and into aqueous acceptor phase and then they were adsorbed on the solid sorbent, which acts as the cathode. Effective parameters such as composition of organic liquid membrane, pH of donor and acceptor phases, applied voltage and extraction time were optimized for extraction of amitriptyline (AMI) and doxepin (DOX) as model analytes and figures of merit of the method were investigated in pure water, human plasma, and urine samples. To extract the model analytes from 24 mL neutral sample solution across organic liquid membrane and into aqueous acceptor phase, 120 V electrical potential was applied for 20 min and finally the drugs were adsorbed on a carbonaceous cathode. Regardless of high sample cleanup, which make the proposed method suitable for the analysis of drugs from complicated matrices, extraction efficiencies in the range of 3.1-11.5% and good detection limits (less than 5 ngmL(-1)) with admissible repeatability and reproducibility (intra- and inter-assay precisions ranged between 4.0-8.5% and 7.5-12.2%, respectively) were obtained from different extraction media. Linearity of the method was studied in the range of 2.0-500.0 ngmL(-1) and 5.0-500.0 ngmL(-1) for AMI and DOX, respectively and coefficient of determination higher than 0.9947 were achieved. Finally, the proposed method was applied for the analysis of AMI and DOX in real samples.

Fatal doxepin intoxication--suicide or slow gradual intoxication?

The differentiation of intoxication courses is one of the most difficult challenges for forensic pathologists and toxicologists. The case of a 52-year-old female inpatient of a psychiatric clinic with multiple medications who died from doxepin intoxication is reported. Concentrations of doxepin metabolites and isomers, pharmacokinetic modelling and genotyping of the doxepin-metabolizing cytochrome P450 (CYP) enzymes led to the following conclusion: the lethal doxepin concentration of 2100 ng/mL was more likely to have been reached due to drug interactions and genetic peculiarities leading to a reduction of the metabolic capacity and not by an acute (suicidal) overdose.

Doxepin concentrations in plasma and cerebrospinal fluid.

Doxepin--like other antidepressant drugs (ADs)--shows a variable antidepressant effect in clinical practice. The cause for this variability is as yet unclear; however, pharmacokinetic factors such as the variable permeability of doxepin into the cerebrospinal fluid (CSF), may contribute to the difference in therapeutic efficacy. We measured and correlated the concentration of doxepin and its active metabolite nordoxepin in both the plasma and CSF. Plasma and CSF samples were taken simultaneously from 21 patients who were treated with doxepin due to different clinical indications. The plasma concentration of both doxepin and nordoxepin correlated significantly with the oral dosage of doxepin (doxepin: r = +0.66, p < 0.001; nordoxepin: r = +0.78, p < 0.0001; Spearman's correlation). Furthermore, we found significant correlations between the plasma and CSF concentrations of both doxepin (r = +0.71; p < 0.001; Pearson's correlation) and nordoxepin (r = +0.74; p < 0.001). These highly significant correlations between the plasma and CSF concentrations indicate a constant CSF permeability of doxepin and its active metabolite nordoxepin.

[Determination of doxepin in whole blood by SPE-LC-MS/MS].

OBJECTIVE: To develop a method of SPE-LC-MS/MS for the determination of doxepin in whole blood. METHODS: After solid phase extraction, the samples were identified by LC-MS/MS. Positive ion electrospray ionization mode and multiple reaction monitoring (MRM) mode was selected. Amitriptyline was used as internal standard. The m/z of doxepin: 280-->107, 280-->235 and 280-->220. The m/z of amitriptyline: 278-->233. The retaining time of doxepin and amitriptyline were 15.15 and 16.94 min, respectively. RESULTS: The calibration curve was linear among the concentration of doxepin range from 0.005 to 1.00 microg/mL. The linear correlation equation was y = 3.2047x + 0.0339, the correlation coefficient was 0.9996. The detection limit of doxepin was 0.001 microg/mL and average recovery rate was 78.0%-82.9%. The relative standard precision for within-day and between-day were less than 2.55% and 5.90%, respectively. CONCLUSION: The method is effective, simple, reliable and can be used in the determination of doxepin in whole blood.

Hypothermia in a combined intoxication with doxepin and moclobemide in an adolescent.

OBJECTIVE: Intoxication with antidepressants, frequently encountered in pediatric emergency medicine, can often lead to life threatening situations. While hyperthermia, hypertonicity and rigidity are symptoms indicative of a serotonin syndrome triggered by an intoxication with serotonin reuptake inhibitors or monoamine oxidase inhibitors, cardiotoxicity, coma and ECG changes are typical of an intoxication with tricyclic antidepressants. CASE REPORT: Hypothermia (instead of the expected hyperthermia) is described for the first time as a persistent symptom during the course of a combined moclobemide-doxepin intoxication in an attempted suicide of a 16-year-old adolescent. DISCUSSION: The administration of serotonin reuptake inhibitors alone or in combination with other medication which increases the level of 5-hydroxytryptamine, i.e. serotonin, in the synaptic cleft mainly leads to hyperthermia. According to a recent study, however, the application of a selective 5-HT(1a) agonist to transgenic mice with a prominent overexpression of the 5-HT(1a) receptor lead to immobility and hypothermia. These findings might help to explain the hypothermia observed in the case of the intoxicated 16-year-old. CONCLUSION: Intoxication with antidepressants should not be excluded a priori in a hypothermic patient who displays other clinical signs of the said intoxication.

The evaluation of doxepin concentrations in postmortem blood as optional cause of death.

The problems concerning an unstable data basis with regard to lethal Doxepin concentrations have been manifested based on a case about a 39-year-old man, who was found dead in his apartment with strangulation marks on his neck, for which a lethal Doxepin intoxication entered the differential diagnosis discussion. For a long time it has been known that postmortem redistribution leads to a falsely inflated concentration as measured in cardiac blood, while the concentrations in peripheral postmortem blood change comparatively little. Despite this, most of the current literature relies on published case report, which fails to mention the location of blood sampling, whereby it is fairly safe to assume that a central sample is intended. Only 9 cases of an isolated lethal Doxepin intoxication have been found, in which the concentrations in blood samples from peripheral vessels had been measured. These values lie between 1.5 and 7.0 mg/L, which is in the lowest quarter of the span of lethal concentrations mentioned in literature without specific mention of the location of the blood sample.

A fatal doxepin poisoning associated with a defective CYP2D6 genotype.

It has been suggested that the polymorphism of the CYP2D6 gene can contribute to occurrence of fatal adverse effects. We therefore investigated postmortem toxicology cases of fatal drug poisonings related to CYP2D6 substrates, with the manner of death denoted as accidental or undetermined. CYP2D6 genotypes were determined in 11 consecutive cases with samples available for DNA analysis. A case of fatal doxepin poisoning with an undetermined manner of death was found to coincide with a completely nonfunctional CYP2D6 genotype (*3/*4), indicating a total absence of CYP2D6 enzyme and suggesting a poor metabolizer phenotype. The doxepin concentration was 2.4 mg/L, the concentration of nordoxepin 2.9 mg/L, and the doxepin/nordoxepin ratio 0.83, the lowest found among the 35 nordoxepin-positive postmortem cases analyzed during the same year. No alcohols or other drugs were detected in the case. The CYP2C19 genotype was determined as that of an extensive metabolizer. The high N-desmethylmetabolite concentration is not consistent with acute intoxication. It is therefore probable that the defective genotype has contributed to the death, possibly involving repeated high dosage of doxepin. Our case strongly emphasizes that a pharmacogenetic analysis in postmortem forensic setting may reveal new insight to the cause or manner of death.

[Intoxication with a tricyclic antidepressant]. / Intoxikation mit einem trizyklischen Antidepressivum.

A 48-year-old woman with a major depression and treatment with doxepin was found comatose in her flat. Her son last saw her 48 h prior to being found. On arrival of the emergency physician, she presented a generalized seizure. The patient underwent endotracheal intubation and mechanical ventilation due to respiratory insufficiency and severe cyanosis. Empty packages of tablets (doxepin ca. 4000 mg and zolpidem 100 mg) were found in the flat. On hospital admission the doxepin blood concentration was 1.2 microg/ml. No life-threatening arrhythmia occurred at any time. On the advice of the poison information center, hemoperfusion was performed for extracorporeal elimination. Within several hours the doxepin blood concentration could be lowered to 0.8 microg/ml and although still above the therapeutic range the patient was extubated. However, the patient developed a generalized seizure which required re-intubation. As a consequence of the high distribution volume and re-distribution phenomena, the doxepin blood concentration had increased again to 1.2 microg/ml. Approximately 72 h later she was extubated again while the doxepin blood concentration was 0.9 microg/ml and 3 days later, the doxepin blood concentration was lowered to 0.3 microg/ml and the patient was transferred to the psychiatric ward the following day. This case report questions the efficacy of hemoperfusion during acute doxepin intoxication in the given constellation of a non-life-threatening arrhythmia.

[Analysis of 37 drugs in whole blood by HPLC after solid phase extraction].

OBJECTIVE: To develop a specific, sensitive, reproducible SPE-HPLC method for the determination of 37 drugs in whole blood. METHODS: With the doxapram as internal standard, Oasis column was used to extract drugs from whole blood. Two kinds of mobile phases were used in this study. Separations were achieved by a LiChrospher 100 RP-C18 (250 mm x 4.0 mm x 5 microm) column kept at 50 degrees C, the DAD detector was set at 230 nm and 250 nm. RESULTS: The limit of detection were 1-30 ng/mL. The method showed excellent linearity and the linear correlation coefficient was > or =0.997 98. The relative standard deviation for between-day and within-day assay were <10%. CONCLUSION: The method is effective, simple, reliable and has been used in real cases.

A comparative solid-phase extraction study for the simultaneous determination of fluvoxamine, mianserin, doxepin, citalopram, paroxetine, and etoperidone in whole blood by capillary gas-liquid chromatography with nitrogen-phosphorus detection.

This paper reports a simple and reliable gas chromatographic method with nitrogen-phosphorus detection without derivatization for the simultaneous detection of fluvoxamine, mianserin, doxepin, citalopram, paroxetine, and etoperidone in whole blood as part of a systematic toxicological analysis (STA). All drugs were studied at concentration levels of 100-2000 ng/mL, except paroxetine for which it was necessary to study at concentration levels of 400-8000 ng/mL. A comparative and validation study using two solid-phase extraction (SPE) columns, Chem Elut and Bond Elut Certify, was developed regarding their recovery, precision, sensitivity, and matrix purification efficiency. The Chem Elut columns, diatomaceous earth, are closely related to conventional liquid-liquid extraction. The Bond Elut Certify columns, more recently developed in the market, are mixed SPE (reversed-phase and cation exchange sorbent). Recoveries for the antidepressants using Chem Elut columns at 500 ng/mL (2000 ng/mL for paroxetine) were in the range 43-72% with intra- and interassay precisions of less than 10% and 16%, respectively. Limits of detection (LODs) and quantitation (LOQs) for fluvoxamine, mianserin, doxepin, citalopram, and etoperidone ranged from 18 to 236 ng/mL and 60 to 786 ng/mL, respectively. LOD and LOQ for paroxetine were 303 and 1009 ng/mL, respectively. Recoveries of these compounds using Bond Elut Certify columns at 500 ng/mL (2000 ng/mL for paroxetine) were in the range 52-83% with intra- and interassay precisions of less than 6% and 8%, respectively. LODs and LOQs for fluvoxamine, mianserin, doxepin, citalopram, and etoperidone ranged from 7 to 28 ng/mL and 23 to 93 ng/mL, respectively. LOD and LOQ for paroxetine were 113 and 376 ng/mL, respectively. An excellent linearity was observed with both procedures from the LOQs up to the upper studied concentration level. In general, higher recoveries, cleaner extracts, better sensitivity, better precision, and reduced solvent consumption and disposal were achieved for the screening of these antidepressants with the use of the mixed SPE Bond Elut Certify compared with Chem Elut columns. The application of these methods on a forensic case study is also presented.