Selective electrochemical detection of antidepressant drug imipramine in blood serum and urine samples using an antimony telluride-graphite nanofiber electrode.

A high-performance imipramine (IMPR) sensor has been developed  based on metal chalcogenide-carbon composite materials. The antimony telluride-graphite nanofiber (Sb2Te3-GNF, hereafter SBT-GNF) composite was synthesized by the hydrothermal method and confirmed by X-ray powder diffraction (XRD) pattern. The morphology, crystalline lattice, and chemical states were characterized by HRTEM, SAED, and XPS analysis. The characterizations confirmed the formation of an effective composite, SBT-GNF. The SBT-GNF was fabricated as a disposable sensor electrode with a screen-printed carbon electrode (SPCE) and examined for the detection of IMPR by differential pulse voltammetry (DPV). The electroanalytical results of SBT-GNF are compared with the SBT and GNF, and the rational design of effective composite is discussed. SBT-GNF/SPCE showed a good linear range (0.01­51.8 µM), sensitivity (1.35 ± 0.1 µA µM-1 cm-2), and low LOD (4 ± 2 nM). Moreover, the SBT-GNF/SPCE revealed high selectivity and high tolerance limit against potential interfering compounds in blood serum and urine samples. Therefore, this electrochemical sensor can be applicable for the detection of tricyclic antidepressant drug IMPR in clinical and pharmaceutical analysis.

A biomimetic hybrid material consisting of CaCO3 mesoporous microspheres and an alternating copolymer for reversed-phase HPLC.

We developed a biomineral-inspired hybrid material composed of CaCO3 and an organic polymer as a column packing material for HPLC. This material combines a hierarchical mesoporous structure and the functionality of the polymer. The surface of monodispersed mesoporous CaCO3 microspheres was modified with poly(maleic acid-alt-1-octadecene) (PMAcO) comprising hydrophobic alkyl chains and anionic carboxylate groups. PMAcO adsorbed onto the surface of CaCO3 through electrostatic interaction between Ca2+ sites and carboxylate groups, resulting in an octadecene coated microsphere interface. These microspheres were applied as a HPLC column and exhibited reversed-phase retention behavior in the separation of alkylbenzenes. This column showed high alkaline mobile phase resistance compared with the conventionally applied ODS column packing material. Quantitative analysis of the basic antidepressants clomipramine and imipramine spiked into whole blood was achieved with an alkaline mobile phase, demonstrating the potential of the biomineral-inspired material as a HPLC stationary phase for practical applications in routine analyses of basic drugs requiring alkaline mobile phases.

Simple and green synthesis of carbon dots (CDs) from valerian root and application of modified mesoporous boehmite (AlOOH) with CDs as a fluorescence probe for determination of imipramine.

A novel, sensitive, rapid, and simple fluorescent probe has been developed based on green-synthesized carbon dots (CDs). In this work, CDs have been synthesized from valerian root by hydrothermal method. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) results confirm the formation of CDs with sizes of less than 10 nm. Fluorescence quenching of CDs was due to the aggregation of the negative charges of CDs with the positive charge of imipramine (IMI) and was then used as the signal for determination of IMI. In addition, the cytotoxicity of CDs was determined using the MTT assay. The probe responses under optimum conditions were linear in the range of 1.0-200.0 ng mL-1 with a limit of detection of 0.6 ng mL-1. Afterwards, mesoporous boehmite (MB) was modified with synthesized CDs (CDs/MB). TEM images confirmed MB modification with CDs. In this case, the variations in the fluorescence signal for different concentrations of IMI increased leading to the higher sensitivity for IMI detection. The limit of detection and linear range for determination of IMI with CDs/MB were obtained as 0.2 and 0.5-200.0 ng mL-1, respectively. To evaluate the fluorescent probe, IMI was measured in real samples. Graphical abstract.

Super paramagnetic core-shells anchored onto silica grafted with C8/NH2 nano-particles for ultrasound-assisted magnetic solid phase extraction of imipramine and desipramine from plasma.

In current work the Fe3O4 magnetic nano-particles anchored to core-shells of SiO2 which grafted by C8/NH2 dual mixed groups, have been synthesized. The magnetic nano-particles were characterized by scanning electron microscopy, X-ray diffraction spectroscopy, and zeta-potential reader. The resulted nano-particles have spherical structure with diameters in the range of 105 to 110 nm. A magnetic solid phase extraction method was developed for extraction of imipramine and desipramine from human plasma samples under ultrasonic conditions by using of prepared NPs as sorbent. The MNPs were dispersion in plasma under sonicated conditions, accumulated by an external magnetic field and washed with Briton-Robinson buffer-acetonitrile solution (0.05 mol l-1, pH = 5, 10%V/V). The drugs were removed by methanol and quantified by gas chromatography. The calibration curves (correlation coefficient > 0.99) for IMP and DES were linear in the concentration range of 0.005 to 5 and 0.01 to 4 µg ml-1, respectively. The LOD, LOQ, intra and inter-day precision values were measured too. The proposed Fe3O4/SiO2/C8/NH2 MNPs could be applied for 3.0 times.

The Impact of Serum Drug Concentration on the Efficacy of Imipramine, Pregabalin, and their Combination in Painful Polyneuropathy.

OBJECTIVE: The aim of this study was to explore the serum concentration-effect relation for first-line drugs in neuropathic pain and to determine if efficacy could be increased. METHODS: Data from a randomized, placebo-controlled, cross-over trial on imipramine, pregabalin, and their combination in painful polyneuropathy were used. Treatment periods were of 4 weeks' duration, outcome was the weekly median of daily pain rated by a 0 to 10 numeric scale, and drug concentrations were determined by high-performance liquid chromatography. RESULTS: In 47 patients, pain was reduced -1.0 (95% confidence interval [CI], -1.5 to -0.6) by imipramine, -0.4 (95% CI, -0.9 to 0.1) by pregabalin, and -1.6 (95% CI, -2.1 to -1.1) by combination therapy. On monotherapy, there was no difference between responders and nonresponders with respect to concentrations of imipramine (mean, 161 vs. 229 nmol/L, P=0.129) and pregabalin (mean, 9.8 vs. 11.7 µmol/L, P=0.178). There was no correlation between drug concentration and pain reduction for imipramine (r=0.17, P=0.247), whereas there was a marginally, positive correlation for pregabalin (r=0.28, P=0.057). There was no interaction between treatment and concentration classes (imipramine < or ≥100 nmol/L, pregabalin < or ≥10 µmol/L) either for monotherapy or for combination therapy (P=0.161 to 0.797). Isobolographic presentations of reponders with imipramine and pregabalin concentrations during combination therapy did not indicate synergistic interaction. DISCUSSION: There were no important relations between drug concentrations and efficacy, or indication of synergistic interaction between the drugs. It was not concluded that treatment can be improved by measurement of drug concentration of pregabalin.

A Simple, Rapid and Reliable Method to Determine Imipramine and Desipramine in Mouse Serum Using Ultra-High-Performance Liquid Chromatography-Quadrupole-Time-of-Flight Mass Spectrometry.

A rapid and sensitive ultra-high-performance liquid chromatography-quadrupole-time-of-flight mass spectrometric (UHPLC-Q-TOF-MS) method was developed for quantification of imipramine, one of the most widely used tricyclic antidepressants, and desipramine, an active metabolite of imipramine, in mouse serum. The developed method included a simple protein precipitation with acetonitrile in 50 µL of serum and analyte separation on an Acquity UPLC BEH C18 column using a gradient elution of acetonitrile with 0.1% formic acid and 20 mM ammonium formate. As a result, the entire analysis time was <20 min including the sample preparation and the LC-MS analysis. The limit of quantification was 5.0 ng mL(-1) for both imipramine and desipramine, and calibration curves were linear over the concentration range of 5.0-1,000.0 and 5.0-250.0 ng mL(-1) for imipramine and desipramine, respectively. Intraday precisions at three levels were 2.2-3.6 and 1.7-4.2% for imipramine and desipramine, respectively, whereas interday precisions were 2.6-5.0 and 2.0-8.4% for imipramine and desipramine, respectively. Accuracy ranged between 93.6 and 106.6% for imipramine and 94.1 and 106.4% for desipramine. Absolute recovery was 96.0-97.6% for imipramine and 87.0-99.5% for desipramine. Finally, the described method was applied to mice administered with imipramine, demonstrating the suitability for quantification of imipramine and desipramine for therapeutic drug monitoring or bioequivalence studies.

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%.

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.

Magnetic beads as an extraction medium for simultaneous quantification of acetaminophen and structurally related compounds in human serum.

This paper describes a sample preparation method that complements a previously published liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay for acetaminophen and eight structurally-related compounds in human serum (C. Bylda, R. Thiele, U. Kobold, D.A. Volmer. Drug Test. Anal. 2014, 6, 451). The analytes (acetaminophen [APAP] + metabolites acetaminophen-glucuronide [APG], -cysteine [APC], -mercapturate [APM] and -cysteine [APC], structurally similar analogues phenacetin and p-phenetidine, as well as tricyclic antidepressants imipramine and amitryptiline) were extracted from serum using magnetized hyper-crosslinked polystyrene particles. The sample preparation protocol was developed by means of a design of experiments (DoE) statistical approach. Using three representative compounds from the analyte panel with different polarities (high, medium, and low), two screening designs were used to identify factors that exhibited significant impact on recovery of the analytes. These parameters were then optimized to permit extraction of the complete target panel exhibiting a broad range of chemical polarities. Liquid chromatographic separations were achieved by gradient elution using a pentafluorphenyl column with subsequent detection by electrospray ionization-triple quadrupole mass spectrometry in multiple reaction monitoring (MRM) mode. The method was linear over the range 0.1-100 µg/mL for APAP, APG, p-phenetidine and phenacetin, 0.03-50 µg/mL for APS, and 0.01-10 µg/mL for APM, APC, imipramine and amitriptyline, with R(2) > 0.99. The assay exhibited good precision with CVs ranging from 2 to 9% for all analytes; the accuracy was assessed by comparing two LC-MS/MS methods using a set of 68 patient samples.

Rapid LC-MS/MS method for determination of drotaverine in a bioequivalence study.

A liquid chromatography coupled with tandem mass spectrometry method for the quantification of the antispasmodic drug drotaverine in human plasma was developed and validated according to the current bioanalytical guidelines. The internal standard used was imipramine. The separation was performed on a Kinetex C18 50×3mm, 2.6µm column under isocratic conditions using a mobile phase of 65:35 (v/v) formic acid 0.2% (v/v) in water and acetonitrile at 40°C with a flow rate of 0.4ml/min. The detection of drotaverine and the internal standard was performed in multiple reaction monitoring (MRM) mode using an ion trap mass spectrometer with electrospray ionization, operating in positive mode. The human plasma samples (0.24ml) were deproteinized with methanol and aliquots of 4µl from supernatants obtained after centrifugation were directly injected into the chromatographic system. The method shows a good linearity (r(2)>0.997), precision (CV<6.3%) and accuracy (bias<5.4%) over the range of 2.24-448ng/ml drotaverine in plasma. The recovery was between 91 and 98%. The limit of quantification was 2.24ng/ml. The analysis required only a 3.0min run. The developed and validated method for the determination of drotaverine in human plasma was successfully applied in a bioequivalence study, for analyzing approximately 1000 subject's samples.

Simultaneous quantification of acetaminophen and structurally related compounds in human serum and plasma.

The method described in this study allows the simultaneous quantification of acetaminophen (APAP) and nine structurally related compounds, namely acetaminophen metabolites and structurally similar analogs (acetaminophen-glucuronide [APG], -sulfate [APS], mercapturate [APM], -cysteine [APC], p-phenetidine, phenacetin), antidote (N-acetylcysteine, NAC), and two tricyclic antidepressants (imipramine and amitryptiline). Due to the relatively high serum concentration levels in the µg/ml range, matrix effects were simply minimized by dilution. The samples were diluted with water and disulfide bonds between serum proteins and analytes reduced using tris(2-carboxyethyl)phosphine. Chromatographic separation of the analytes was achieved by gradient elution using a pentafluorphenyl (PFP) column with subsequent detection by electrospray ionization (ESI) triple quadrupole mass spectrometry in positive and negative ionization multiple reaction monitoring (MRM) modes. Quantification was performed by means of deuterated analogues of the analytes as internal standards. Total run time of the assay was 19 min. The method was fully validated and allowed quantification of the analytes with lower limits of quantification between 50 and 0.5 ng/ml. The calibration curves were linear over the range 0.1-100 µg/ml for APAP, APG, NAC, p-phenetidine and phenacetin, 0.03-50 µg/ml for APS, and 0.01-10 µg/ml for APM, APC, imipramine and amitriptyline with correlation coefficients r(2) > 0.99. The intra-assay precision was ≤5% for all analytes except NAC (CV < 10%). The inter-day precision was ≤10% for all analytes except NAC (inter-assay precision <11%). This method was used to analyze 77 patient and spiked samples and results were consistent with expected values from a round robin test.

A double-blind randomized study comparing plasma level-targeted dose imipramine and high-dose venlafaxine in depressed inpatients.

OBJECTIVE: To compare the efficacy of plasma level-targeted dose imipramine and high-dose venlafaxine in depressed inpatients in a randomized double-blind study. METHODS: The study included 85 patients with a diagnosis of major depressive episode according to the DSM IV criteria and a 17-item Hamilton Rating Scale for Depression (HAM-D) score ≥ 17. Patients were randomized to imipramine or venlafaxine. The dose of imipramine was adjusted for each patient to a predefined blood level of 200-300 ng/ml. The dose of venlafaxine was increased gradually to 300-375 mg/day. Efficacy was evaluated after 7 weeks of treatment. RESULTS: The mean age of the study group was 54.5 (range 29-82) years. There was no significant difference according to the primary outcome criterion of a ≥50% reduction on the HAM-D score: 17 of 43 (39.5%) patients on imipramine were responders compared to 21 of 42 (50%) patients on venlafaxine. When considering remission as outcome criterion (HAM-D score ≤ 7), 10 of 43 (23.3%) patients on imipramine were remitters compared to 15 of 42 (35.7%) patients on venlafaxine; again, no significant difference. When analysing a subpopulation of patients without psychotic features, with remission as outcome criterion, a significant difference was found: 5 of 34 (14.7%) patients on imipramine were remitters compared to 12 of 31 (38.7%) patients on venlafaxine. CONCLUSIONS: The present study used optimal doses in depressed inpatients and showed that venlafaxine is at least equal in efficacy to imipramine. The results in the subgroup without psychotic features indicate a possible superiority of venlafaxine.

Adsorptive stripping voltammetric determination of imipramine, trimipramine and desipramine employing titanium dioxide nanoparticles and an Amberlite XAD-2 modified glassy carbon paste electrode.

An Amberlite XAD-2 (XAD2) and titanium dioxide nanoparticles (TNPs) modified glassy carbon paste electrode (XAD2-TNP-GCPE) was developed for the determination of imipramine (IMI), trimipramine (TRI) and desipramine (DES). The electrochemical behavior of these molecules was investigated employing cyclic voltammetry (CV), chronocoulometry (CC), electrochemical impedance spectroscopy (EIS) and adsorptive stripping differential pulse voltammetry (AdSDPV). After optimization of analytical conditions using a XAD2-TNP-GCPE electrode at pH 6.0 phosphate buffer (0.1 M), the peak currents were found to vary linearly with its concentration in the range of 1.30 × 10(-9) to 6.23 × 10(-6) M for IMI, 1.16 × 10(-9) to 6.87 × 10(-6) M for TRI and 1.43 × 10(-9) to 5.68 × 10(-6) M for DES. The detection limits (S/N = 3) of 3.93 × 10(-10), 3.51 × 10(-10) and 4.35 × 10(-10) M were obtained for IMI, TRI and DES respectively using AdSDPV. The prepared modified electrode showed several advantages such as a simple preparation method, high sensitivity, very low detection limits and excellent reproducibility. The proposed method was employed for the determination of IMI, TRI and DES in pharmaceutical formulations, blood serum and urine samples.

Electromembrane extraction combined with gas chromatography for quantification of tricyclic antidepressants in human body fluids.

Recent advances in electromembrane extraction (EME) methodology calls for effective and accessible detection methods. Using imipramine and clomipramine as model therapeutics, this proof-of-principle work combines EME with gas chromatography analysis employing a flame ionization detector (FID). The drugs were extracted from acidic aqueous sample solutions, through a supported liquid membrane (SLM) consisting of 2-nitrophenyl octyl ether (NPOE) impregnated on the walls of the hollow fiber. EME parameters, such as SLM composition, type of ion carrier, pH and the composition of donor and acceptor solutions, agitation speed, extraction voltage, and extraction time were studied in detail. Under optimized conditions, the therapeutics were effectively extracted from different matrices with recoveries ranging from 90 to 95%. The samples were preconcentrated 270-280 times prior to GC analysis. Reliable linearity was also achieved for calibration curves with a regression coefficient of at least 0.995. Detection limits and intra-day precision (n=3) were less than 0.7 ng mL(-1) and 8.5%, respectively. Finally, method was applied to determination and quantification of drugs in human plasma and urine samples and satisfactory results were achieved.

Simultaneous generation of binary and normal data with specified marginal and association structures.

Situations in which multiple outcomes and predictors of different distributional types are collected are becoming increasingly common in biopharmaceutical practice, and joint modeling of mixed types has been gaining popularity in recent years. Evaluation of various statistical techniques that have been developed for mixed data in simulated environments necessarily requires joint generation of multiple variables. This article is concerned with building a unified framework for simulating multiple binary and normal variables simultaneously given marginal characteristics and association structure via combining well-established results from the random number generation literature. We illustrate the proposed approach in two simulation settings where we use artificial data as well as real depression score data from psychiatric research, demonstrating a very close resemblance between the specified and empirically computed statistical quantities of interest through descriptive and model-based tools.

Inhibition of P-glycoprotein enhances transport of imipramine across the blood-brain barrier: microdialysis studies in conscious freely moving rats.

BACKGROUND AND PURPOSE: Recent studies indicate that efflux of antidepressants by the multidrug resistance transporter P-glycoprotein (P-gp) at the blood-brain barrier (BBB) may contribute to treatment-resistant depression (TRD) by limiting intracerebral antidepressant concentrations. In addition, clinical experience shows that adjunctive treatment with the P-gp inhibitor verapamil may improve the clinical outcome in TRD. Therefore, the present study aimed to investigate the effect of P-gp inhibition on the transport of the tricyclic antidepressant imipramine and its active metabolite desipramine across the BBB. EXPERIMENTAL APPROACH: Intracerebral microdialysis in rats was used to monitor brain levels of imipramine and desipramine following i.v. imipramine administration, with or without pretreatment with one of the P-gp inhibitors verapamil or cyclosporin A (CsA). Plasma drug levels were also determined at regular intervals. KEY RESULTS: Pretreatment with either verapamil or CsA resulted in significant increases in imipramine concentrations in the microdialysis samples, without altering imipramine plasma pharmacokinetics. Furthermore, pretreatment with verapamil, but not CsA, led to a significant elevation in plasma and brain levels of desipramine. CONCLUSIONS AND IMPLICATIONS: The present study demonstrated that P-gp inhibition enhanced the intracerebral concentration of imipramine , thus supporting the hypothesis that P-gp activity restricts brain levels of certain antidepressants, including imipramine. These findings may help to explain reports of a beneficial response to adjunctive therapy with verapamil in TRD.

Exploration of a new concept for automated dried blood spot analysis using flow-through desorption and online SPE-MS/MS.

BACKGROUND: A new concept for simple and generic automation of dried blood spot (DBS) analysis is evaluated. Flow-through desorption of the blood spot is coupled online to SPE and MS/MS without using a LC column. Blood, spiked with a mixture of test compounds is spotted on paper, dried and then desorbed by means of a prototype clamping device. RESULTS: Conditions for extraction and chromatography on a single SPE cartridge were optimized with respect to clean-up, separation and ionization suppression. Addition of internal standard using loop-injection upstream of the clamped blood spot was examined and proved to be simple and reliable. Validation results for the 1-1000 ng/ml range are well within acceptance criteria for bioanalysis. CONCLUSION: Results demonstrate feasibility of the DBS SPE-MS/MS concept for efficient automation of the entire DBS analysis workflow.

Evaluation of the potential of surface enhancement Raman spectroscopy for detection of tricyclic psychotropic drugs. Case studies on imipramine and its metabolite.

The potential use of surface Raman enhanced spectroscopy (SERS) for confirmatory identification and the semi-quantitative analysis of selected tricyclic antidepressants (TCAs) is examined utilizing a conventional silver colloid. Raman and SERS spectra of aqueous solutions of imipramine (Imi) and its metabolite, desipramine (Des), were recorded as the function of concentration using NIR excitation. A good linear correlation is observed for the dependence of the SERS signal at 684 cm(-1) (R(2) = 0.9997) on Imi concentration over the range of 0.75-7.5 µM. The limit of detection of imipramine in the silver colloidal solution is 0.98 µM. SERS spectra of Imi and Des were also recorded for blood plasma samples without prior purification as well as after the use of standard solid phase extraction. All spectra show the characteristic spectral profile of the molecules and moreover, stronger signal enhancement is observed for Imi in the "raw" samples as opposed to Imi extracted from a biological matrix.

Ultra-high capacity liquid chromatography chip/quadrupole time-of-flight mass spectrometry for pharmaceutical analysis.

Nanoflow liquid chromatography/mass spectrometry (nano-LC/MS) has attracted increasing interest in virtue of high sensitivity, low sample consumption, and minimal matrix effect. In this work a HPLC-Chip/quadrupole time-of-flight (Q-TOF) MS device with a new ultra-high capacity small molecule chip (UHC-Chip) which features a 500 nL enrichment column and a 150 mm × 75 µm analytical column, was evaluated with a drug mixture covering a wide range of polarities. Excellent chromatographic precision with 0.1-0.5% RSD for retention time and 1.7-9.0% RSD for peak area, low limit of detection, good chip-to-chip reproducibility and linearity were obtained by using this UHC-Chip. Compared with the standard HPLC-Chip with 40 nL trapping column, the UHC-Chip showed higher enrichment capability and hence gave a higher response in signal detection. Additionally, 4-30 times increase in sensitivity was obtained compared with conventional LC/MS, which indicated that UHC-Chip/MS was a valuable tool for the quantitative analysis of low level impurities and degradation products in pharmaceuticals. Moreover, satisfactory results obtained from trace drug analysis of serum samples further proved its practicality and potential for use in drug testing and development.

In vivo canine model comparison of cardiovascular effects of antidepressants milnacipran and imipramine.

Milnacipran is a specific serotonin and norepinephrine reuptake inhibitor, which has been widely used against major depressive episodes. In this study, cardiovascular effects of milnacipran were assessed in comparison with those of a typical tricyclic antidepressant imipramine using the halothane-anesthetized dogs. Milnacipran (n = 6) or imipramine (n = 6) was intravenously administrated in three escalating doses of 0.1, 1 and 10 mg/kg over 10 min with a pause of 20 min between the doses. Clinically relevant plasma concentrations were obtained after 0.1-1 mg/kg of milnacipran in this study, whereas therapeutic dose and plasma concentration of imipramine were reported to be similar to those of milnacipran. The low and middle doses of milnacipran hardly affected cardiohemodynamic or electrophysiological variables except that they slightly increased vascular tone and ventricular contraction, whereas same doses of imipramine delayed repolarization process without affecting the other variables. The high dose of both milnacipran and imipramine induced similar extent of negative chronotropic, inotropic and dromotropic effects together with vasoconstriction and repolarization delay. Thus, the effects of milnacipran may be more selective for cardiohemodynamics than for repolarization delay, whereas reverse will be true for imipramine, supporting lack of clinical report of patients with milnacipran-induced long QT syndrome unlike imipramine.