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.

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.

Commutability of proficiency testing material containing amitriptyline and nortriptyline: A study within the framework of the Dutch Calibration 2.000 project.

BACKGROUND: External quality assessment schemes (EQAS) can provide important information regarding accuracy and comparability of different measurement methods if the sample matrices are composed of commutable material. The aim of this study was to assess the commutability of different matrices for the material used in an EQAS for amitriptyline and nortriptyline. METHODS: Proficiency testing material (PTM) and patient samples containing amitriptyline and nortriptyline were prepared, collected, pooled, and distributed to participating laboratories for analysis. Low, medium and high concentrations of both drugs in liquid pooled human, lyophilized human and lyophilized bovine serum were tested in this study. The measurement deviation of the PTM results to the patient serum regression line were normalized by dividing trough the average within-laboratory SD (SDwl) derived from the results reported in the official EQAS, resulting in a relative residual. The commutability decision limit was set at 3 SDwl. RESULTS: With 10 laboratories participating in this study, 45 laboratory couples were formed. All matrix types delivered several relative residuals outside the commutability decision limit. The number and the magnitude of relative residuals for both drugs were lower for liquid human sera as compared to lyophilized human and bovine sera. CONCLUSIONS: The PTM used for amitriptyline and nortriptyline is preferably prepared with human serum, although not all relative residuals are within the commutability decision limit.

Practical liquid chromatography-tandem mass spectrometry method for the simultaneous quantification of amitriptyline, nortriptyline and their hydroxy metabolites in human serum.

Amitriptyline (AMI) has been in use for decades in treating depression and more recently for the management of neuropathic pain. A highly sensitive and specific LC-tandem mass spectrometry method was developed for simultaneous determination of AMI, its active metabolite nortriptyline (NOR) and their hydroxy-metabolites in human serum, using deuterated AMI and NOR as internal standards. The isobaric E-10-hydroxyamitriptyline (E-OH AMI), Z-10-hydroxyamitriptyline (Z-OH AMI), E-10-hydroxynortriptyline (E-OH NOR) and Z-10-hydroxynortriptyline (Z-OH NOR), together with their parent compounds, were separated on an ACE C18 column using a simple protein precipitation method, followed by dilution and analysis using positive electrospray ionisation with multiple reaction monitoring. The total run time was 6 min with elution of E-OH AMI, E-OH NOR, Z-OH AMI, Z-OH NOR, AMI (+ deuterated AMI) and NOR (+ deuterated NOR) at 1.21, 1.28, 1.66, 1.71, 2.50 and 2.59 min, respectively. The method was validated in human serum with a lower limit of quantitation of 0.5 ng/mL for all analytes. A linear response function was established for the range of concentrations 0.5-400 ng/mL (r2 > .999). The practical assay was applied on samples from patients on AMI, genotyped for CYP2C19 and CYP2D6, to understand the influence of metaboliser status and concomitant medication on therapeutic drug monitoring.

Experimental and Clinical Pharmacokinetics of Fluoxetine and Amitriptyline: Comparative Analysis and Possible Methods of Extrapolation.

The pharmacokinetics of two fluoxetine capsulated dosage forms and two amitriptyline tablet forms after a single oral intake was studied in dogs and healthy volunteers. High significant correlations were detected between plasma concentrations of fluoxetine (r=0.96, p<0.00001, n=11) and amitriptyline (r=0.78, p<0.0224, n=8) in dogs and volunteers. A correlation of medium strength (though insignificant) was detected between nortriptyline concentrations in the plasma of dogs and volunteers (r=0.69, p<0.199, n=5). The bioavailability parameters of the test drugs in dogs and volunteers did not differ. Similar trends of fluoxetine and amitriptyline pharmacokinetic parameters were revealed in volunteers and animals. Methods for extrapolation of experimental pharmacokinetics parameters of fluoxetine and amitriptyline obtained on dogs for humans are proposed and validated.

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.

Pharmacokinetic determination and analysis of nortriptyline based on GC-MS coupled with hollow-fiber drop-to-drop solvent microextraction technique.

AIM: A simple, sensitive and robust technique of hollow-fiber drop-to-drop solvent microextraction coupled with GC-MS has been successfully developed for the detection of antidepressant drug nortriptyline in human blood and urine samples. The recoveries of the drug from the spiked samples are found to be well within the range and appropriate to support the method. RESULTS: The LOD for the drug was obtained to be 0.007, 0.009 and 0.021 µg ml-1 in deionized water, urine and blood samples of human subjects, respectively. Linearity was obtained over the concentration range of 0.5-5.0 mg l-1 in deionized water with correlation coefficient 0.99672.

Limitations of the Anticholinergic Activity Assay and Assay-Based Anticholinergic Drug Scales.

OBJECTIVE: The anticholinergic activity (AA) assay is a common method to determine a patient's anticholinergic load. Several limitations, however, are expected when applying the AA assay to patients or using drug scales to estimate anticholinergic burden based on AA levels. This study aims to demonstrate common pitfalls in an experimental setting and outline their clinical consequences. METHODS: The AA was analyzed for five drugs with reported interaction with muscarinic receptors. Concentration-response curves were constructed for furosemide (weak anticholinergic), diphenhydramine (moderate anticholinergic), the strong anticholinergic amitriptyline and its metabolite nortriptyline, and the cholinergic pilocarpine. The Combination Index (CI) was used to assess the interaction of three drug combinations with amitriptyline. RESULTS: All compounds displaced the radioactive tracer from its receptor binding site in a concentration-dependent manner, and full displacement was reached for all compounds except furosemide (Emax 16%). The CI indicated that amitriptyline and thioridazine have antagonistic effects (CI = 1.46) at low and synergistic effects (CI = 0.88) at higher concentrations (p < 0.0001), whereas synergistic effects (CI = 0.47-0.48) were observed for amitriptyline in any concentration combined with pilocarpine (p < 0.001). CONCLUSION: When the patient's anticholinergic load is estimated using AA levels, the actual exposure, combination of anticholinergic drugs, their active metabolites, and also drugs with an opposite pharmacologic action will contribute to AA levels, whereas weak anticholinergic drugs in therapeutic concentrations are rather negligible.

Quantification of Tricyclic Antidepressants in Serum Using Liquid Chromatography Electrospray Tandem Mass Spectrometry (HPLC-ESI-MS/MS).

Tricyclic antidepressants (TCA) are used to treat major depressive disorder and other psychological conditions. The efficacy of these drugs is tied to a narrow therapeutic window. Inappropriately high drug concentrations can result in serious side effects such as hypotension, tachycardia, or coma. As a result, concentrations of tricyclic antidepressants are routinely monitored to ensure compliance and to prevent adverse side effects by dose adjustments. We describe a method for the determination of concentrations of amitriptyline, desipramine, imipramine, and nortriptyline in human serum using high-performance liquid chromatography coupled to a tandem mass spectrometer with electrospray ionization (HPLC-ESI-MS/MS). The method is rapid, requiring only 3.5 min per analysis. The method requires 100 µL of serum. Concentrations of each TCA were quantified by a calibration curve relating the peak area ratio of each TCA analyte to a deuterated internal standard (amitriptyline-D3, desipramine-D3, imipramine-D3, and nortriptyline-D3). The method was linear from ~70 ng/mL to ~1000 ng/mL for all TCAs, with imprecision ≤ 12%.

Dynamic electromembrane extraction: Automated movement of donor and acceptor phases to improve extraction efficiency.

In the present research, dynamic electromembrane extraction (DEME) was introduced for the first time for extraction and determination of ionizable species from different biological matrices. The setup proposed for DEME provides an efficient, stable, and reproducible method to increase extraction efficiency. This setup consists of a piece of hollow fiber mounted inside a glass flow cell by means of two plastics connector tubes. In this dynamic system, an organic solvent is impregnated into the pores of hollow fiber as supported liquid membrane (SLM); an aqueous acceptor solution is repeatedly pumped into the lumen of hollow fiber by a syringe pump whereas a peristaltic pump is used to move sample solution around the mounted hollow fiber into the flow cell. Two platinum electrodes connected to a power supply are used during extractions which are located into the lumen of the hollow fiber and glass flow cell, respectively. The method was applied for extraction of amitriptyline (AMI) and nortriptyline (NOR) as model analytes from biological fluids. Effective parameters on DEME of the model analytes were investigated and optimized. Under optimized conditions, the calibration curves were linear in the range of 2.0-100µgL(-1) with coefficient of determination (r(2)) more than 0.9902 for both of the analytes. The relative standard deviations (RSD %) were less than 8.4% based on four replicate measurements. LODs less than 1.0µgL(-1) were obtained for both AMI and NOR. The preconcentration factors higher than 83-fold were obtained for the extraction of AMI and NOR in various biological samples.

Evaluation of the pharmacokinetics of oral amitriptyline and its active metabolite nortriptyline in fed and fasted Greyhound dogs.

This study reports the pharmacokinetics of oral amitriptyline and its active metabolite nortriptyline in Greyhound dogs. Five healthy Greyhound dogs were enrolled in a randomized crossover design. A single oral dose of amitriptyline hydrochloride (actual mean dose 8.1 per kg) was administered to fasted or fed dogs. Blood samples were collected at predetermined times from 0 to 24 h after administration, and plasma drug concentrations were measured by liquid chromatography with mass spectrometry. Noncompartmental pharmacokinetic analyses were performed. Two dogs in the fasted group vomited following amitriptyline administration and were excluded from analysis. The range of amitriptyline CMAX for the remaining fasted dogs (n = 3) was 22.8-64.5 ng/mL compared to 30.6-127 ng/mL for the fed dogs (n = 5). The range of the amitriptyline AUCINF for the three fasted dogs was 167-720 h·ng/mL compared to 287-1146 h·ng/mL for fed dogs. The relative bioavailability of amitriptyline in fasted dogs compared to fed dogs was 69-91% (n = 3). The exposure of the active metabolite nortriptyline was correlated to amitriptyline exposure (R(2)  = 0.84). Due to pharmacokinetic variability and the small number of dogs completing this study, further studies are needed assessing the impact of feeding on oral amitriptyline pharmacokinetics. Amitriptyline may be more likely to cause vomiting in fasted dogs.

[The determination of amitriptyline and its metabolite, nortriptyline, in the biological objects of the corpse by the high-performance liquid chromatography technique].

Tricyclic antidepressants are among the preparations that most frequently cause intoxication in adults and children; moreover, poisoning with these substances not infrequently has a fatal outcome. Medications belonging to this group, such as amitriptyline, are extensively used to manage manifestations of depression, anxiety, migraine, neuropathic pain, and hyperactivity syndrome. Amitriptyline overdosage causes non-specific symptoms of intoxication, and its clinical picture does not allow to identify the nature of a psychotropic xenobiotic. Of primary importance in connection with this is to establish the cause of intoxication or death by the clinical toxicological and forensic medical methods based on the results of the fast identification and quantitation of amitriptyline in biological materials including blood, urine, hepatic tissues, etc. The authors describe the method for the determination of amitriptyline and its principal physiological metabolite nortriptyline in biological objects with the help of high performance liquid chromatography (HPLC).

Pharmacokinetics of intravenous and oral amitriptyline and its active metabolite nortriptyline in Greyhound dogs.

OBJECTIVE: To evaluate the pharmacokinetics of amitriptyline and its active metabolite nortriptyline after intravenous (IV) and oral amitriptyline administration in healthy dogs. STUDY DESIGN: Prospective randomized experiment. ANIMALS: Five healthy Greyhound dogs (three males and two females) aged 2-4 years and weighing 32.5-39.7 kg. METHODS: After jugular vein catheterization, dogs were administered a single oral or IV dose of amitriptyline (4 mg kg(-1)). Blood samples were collected at predetermined time points from baseline (0 hours) to 32 hours after administration and plasma concentrations of amitriptyline and nortriptyline were measured by liquid chromatography triple quadrupole mass spectrometry. Non-compartmental pharmacokinetic analyses were performed. RESULTS: Orally administered amitriptyline was well tolerated, but adverse effects were noted after IV administration. The mean maximum plasma concentration (CMAX) of amitriptyline was 27.4 ng mL(-1) at 1 hour and its mean terminal half-life was 4.33 hours following oral amitriptyline. Bioavailability of oral amitriptyline was 6%. The mean CMAX of nortriptyline was 14.4 ng mL(-1) at 2.05 hours and its mean terminal half-life was 6.20 hours following oral amitriptyline. CONCLUSIONS AND CLINICAL RELEVANCE: Amitriptyline at 4 mg kg(-1) administered orally produced low amitriptyline and nortriptyline plasma concentrations. This brings into question whether the currently recommended oral dose of amitriptyline (1-4 mg kg(-1)) is appropriate in dogs.

A simple dried blood spot method for therapeutic drug monitoring of the tricyclic antidepressants amitriptyline, nortriptyline, imipramine, clomipramine, and their active metabolites using LC-MS/MS.

Therapeutic drug monitoring (TDM) of tricyclic antidepressants (TCAs) is considered useful in patients with major depressive disorder, since these drugs display large individual differences in clearance, and the therapeutic windows of these drugs are relatively small. We developed an assay for determination of amitriptyline (ATP), nortriptyline (NTP), imipramine (IMP), desipramine (DSP) clomipramine (CMP) and desmethyl-clomipramine (DCMP) in dried blood spots (DBS). A fast and robust LC-MS/MS method was developed and analytically validated for simultaneous determination of ATP, NTP, IMP, DSP, CMP, and DCMP in DBS. Six mm circles were punched out from DBS collected on Whatman DMPK-C paper and mixed with acetonitrile: methanol 1:3 containing the internal standard. The extract was analyzed by LC-MS/MS. Total LC-MS/MS runtime was 4.8 min. The assay was linear in the range 20-500 µg/L for all compounds. Overall-assay accuracy and precision were<20% for the lower limit of quantification (LLOQ), except for CMP (CV=22.3%), and <15% at other concentrations. The initial LLOQ was 20 µg/L however for CMP and DMCP it was increased to 40 µg/L. The blood volume per spot did not influence the results, but a low hematocrit (≤ 30%) was associated with a >15% negative bias for all compounds. Punching at the perimeter of the blood spot instead of the center was associated with a positive bias. A good correlation was found between patients plasma and DBS samples of ATP, NTP and DMCP, but not for CMP. In addition, proportional differences were found. This LC-MS/MS method was analytically validated for determination of TCAs in DBS. Future validation will focus on the clinical application of the method.

Pharmacokinetic interaction between nevirapine and nortriptyline in rats: inhibition of nevirapine metabolism by nortriptyline.

One of the most frequent comorbidities of HIV infection is depression, with a lifetime prevalence of 22 to 45%. Therefore, it was decided to study a potential pharmacokinetic interaction between the nonnucleoside reverse transcriptase inhibitor nevirapine (NVP) and the tricyclic antidepressant nortriptyline (NT). NVP and NT were administered to rats either orally, intraduodenally, or intravenously, and the changes in plasma levels and pharmacokinetic parameters were analyzed. Experiments with rat and human hepatic microsomes were carried out to evaluate the inhibitory effects of NT on NVP metabolism. NVP plasma concentrations were significantly higher when this drug was coadministered with NT. The maximum plasma concentrations of NVP were increased 2 to 5 times and the total plasma clearance was decreased 7-fold in the presence of NT. However, statistically significant differences in the pharmacokinetic parameters of NT in the absence and presence of NVP were not found. In vitro studies with rat and human hepatic microsomes confirmed the inhibition of NVP hepatic metabolism by NT in a concentration-dependent way, with the inhibition being more intense in the case of rat microsomes. In conclusion, a pharmacokinetic interaction between NVP and NT was detected. This interaction was a consequence of the inhibition of hepatic metabolism of NVP by NT. In vivo human studies are required to evaluate the effects of this interaction on the pharmacokinetics of NVP before it can be taken into account for patients receiving NVP.

Norepinephrine transporter occupancy by nortriptyline in patients with depression: a positron emission tomography study with (S,S)-[¹8F]FMeNER-D2.

Norepinephrine transporter (NET) plays important roles in the treatment of various neuropsychiatric disorders, such as depression and attention deficit hyperactivity disorder (ADHD). Nortriptyline is a NET-selective tricyclic antidepressant (TCAs) that has been widely used for the treatment of depression. Previous positron emission tomography (PET) studies have reported over 80% serotonin transporter occupancy with clinical doses of selective serotonin reuptake inhibitors (SSRIs), but there has been no report of NET occupancy in patients treated with relatively NET-selective antidepressants. In the present study, we used PET and (S,S)-[18¹8F]FMeNER-D2 to investigate NET occupancies in the thalamus in 10 patients with major depressive disorder taking various doses of nortriptyline, who were considered to be responders to the treatment. Reference data for the calculation of occupancy were derived from age-matched healthy controls. The result showed approximately 50-70% NET occupancies in the brain as a result of the administration of 75-200 mg/d of nortriptyline. The estimated effective dose (ED50) and concentration (EC50) required to induce 50% occupancy was 65.9 mg/d and 79.8 ng/ml, respectively. Furthermore, as the minimum therapeutic level of plasma nortriptyline for the treatment of depression has been reported to be 70 ng/ml, our data indicate that this plasma nortriptyline concentration corresponds to approximately 50% NET occupancy measured with PET, suggesting that more than 50% of central NET occupancy would be appropriate for the nortriptyline treatment of patients with depression.

Genetic differences in cytochrome P450 enzymes and antidepressant treatment response.

AIMS: Antidepressant response varies between patients, possibly due to differences in the rate cytochrome P450 enzymes metabolise antidepressants into inactive compounds. Drug metabolism rates are influenced by common variants in the genes encoding these enzymes. However, it remains unclear whether treatment outcomes can be predicted by either CYP450 genotype or antidepressant serum concentration. METHODS: In GENDEP (a pharmacogenetic study of depressed individuals treated with either escitalopram or nortriptyline), serum concentrations of antidepressants and their primary metabolite were measured after eight weeks treatment and variants in CYP2D6 and CYP2C19 were genotyped. RESULTS: Amongst patients taking escitalopram (n=223), the genotype CYP2C19 was significantly associated with escitalopram serum concentrations and desmethylescitalopram:escitalopram ratio. For those taking nortriptyline (n=161), the CYP2D6 genotype was significantly associated with nortriptyline and 10-hydroxynortriptyline serum concentrations and 10-hydroxynortriptyline:nortrip-tyline ratio. CYP450 genotypes conferring greater enzyme activity were linked to lower drug serum concentrations and higher metabolite:drug ratios. Nonetheless, no significant association was found between either CYP450 genotype or antidepressant serum concentration and treatment response. CONCLUSIONS: While there is a significant relationship between the CYP450 genotype and serum concentrations of escitalopram and nortriptyline, the genotypes are not predictive of differences in treatment response for either drug. Furthermore, differences in antidepressant serum concentrations are not associated with variability in treatment response.