Carbon Nanohorn Suprastructures on a Paper Support as a Sorptive Phase.

This article describes a method for the modification of paper with single-wall carbon nanohorns (SWCNHs) to form stable suprastructures. The SWCNHs form stable dahlia-like aggregates in solution that are then self-assembled into superior structures if the solvent is evaporated. Dipping paper sections into a dispersion of SWCNHs leads to the formation of a thin film that can be used for microextraction purposes. The coated paper can be easily handled with a simple pipette tip, paving the way for disposable extraction units. As a proof of concept, the extraction of antidepressants from urine and their determination by direct infusion mass spectrometry is studied. Limits of detection (LODs) were 10 ng/L for desipramine, amitriptyline, and mianserin, while the precision, expressed as a relative standard deviation, was 7.2%, 7.3%, and 9.8%, respectively.

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.

On-Chip Electromembrane Surrounded Solid Phase Microextraction for Determination of Tricyclic Antidepressants from Biological Fluids Using Poly(3,4-ethylenedioxythiophene)-Graphene Oxide Nanocomposite as a Fiber Coating.

In the present study, on-chip electromembrane surrounded solid phase microextraction (EM-SPME) was employed in the determination of tricyclic antidepressants (TCAs), including amitriptyline, nortriptyline, imipramine, desipramine, maprotiline, and sertraline, from various biological fluids. In this regard, poly(3,4-ethylenedioxythiophene)-graphene oxide (PEDOT-GO) was electrodeposited on an SPME fiber as a conductive coating, then the fiber played the acceptor-electrode role during the extraction. Thus, the immigration of the analytes under the influence of an electric field and their absorption onto the fiber coating were accomplished simultaneously. Under the optimized conditions, the limits of detection for the target analytes were acquired in the range of 0.005-0.025 µg L-1 using gas chromatography-mass spectrometry. The linearity of the method was 0.010-500 µg L-1 for the imipramine and sertraline, 0.025-500 µg L-1 for the amitriptyline, nortriptyline, and desipramine, and 1.000-250 µg L-1 for the maprotiline (R2 ≥ 0.9984). Moreover, this method provided suitable precision and fiber-to-fiber reproducibility, with RSDs ≤ 8.4%. The applicability of the proposed setup was eventually investigated for extraction of the drugs from human bone marrow aspirate, urine, plasma, and well water samples, in which satisfactory relative recoveries, from 93-105%, were obtained.

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.

[Two cases of suspected Munchausen by proxy syndrome: the importance of forensic toxicological analyses in handling suspicions and producing evidence]. / Zwei Fälle von vermutetem Münchhausen-Syndrom-by-proxy. Zur Bedeutung forensisch-toxikologischer Analysen bei Verdachtsgewinnung und Beweisfiührung.

The authors report on two cases of suspected Munchausen by proxy syndrome. In a 3-year-old boy, clinical toxicological analyses produced suspicious clues that an antidepressant had been administered, which could not be verified by forensic toxicological investigations. In a 13-month-old boy, the mother was also suspected of having poisoned the child. Initial clinical toxicological examinations failed to explain the observed symptoms (unclear unconsciousness, narrowed pupils). While in the first case, the incorrect interpretation of findings by a laboratory without forensic experience resulted in suspicions against the mother, the cause for the observed symptoms in the second case could be proved by complex analyses not performed before and the suspicion that the clinical picture had been intentionally brought about could be cleared up (use of an antitussive containing clobutinol). The two reports show that especially in cases with a potential forensic background, adequately qualified forensic laboratories with a broad spectrum of analytical methods should be involved.

A Robust Liposomal Platform for Direct Colorimetric Detection of Sphingomyelinase Enzyme and Inhibitors.

The enzyme sphingomyelinase (SMase) is an important biomarker for several diseases such as Niemann Pick's, atherosclerosis, multiple sclerosis, and HIV. We present a two-component colorimetric SMase activity assay that is more sensitive and much faster than currently available commercial assays. Herein, SMase-triggered release of cysteine from a sphingomyelin (SM)-based liposome formulation with 60 mol % cholesterol causes gold nanoparticle (AuNP) aggregation, enabling colorimetric detection of SMase activities as low as 0.02 mU/mL, corresponding to 1.4 pM concentration. While the lipid composition offers a stable, nonleaky liposome platform with minimal background signal, high specificity toward SMase avoids cross-reactivity of other similar phospholipases. Notably, use of an SM-based liposome formulation accurately mimics the natural in vivo substrate: the cell membrane. We studied the physical rearrangement process of the lipid membrane during SMase-mediated hydrolysis of SM to ceramide using small- and wide-angle X-ray scattering. A change in lipid phase from a liquid to gel state bilayer with increasing concentration of ceramide accounts for the observed increase in membrane permeability and consequent release of encapsulated cysteine. We further demonstrated the effectiveness of the sensor in colorimetric screening of small-molecule drug candidates, paving the way for the identification of novel SMase inhibitors in minutes. Taken together, the simplicity, speed, sensitivity, and naked-eye readout of this assay offer huge potential in point-of-care diagnostics and high-throughput drug screening.

The effect of beta-cyclodextrin on liquid chromatography/electrospray-mass spectrometry analysis of hydrophobic drug molecules.

Cyclodextrins (CDs) are widely used in the pharmaceutical industry for their capability of improving bioavailability, solubility, or stability of drugs via the formation of soluble inclusion complexes. CDs have also been widely used in various chemical analysis methods. In this work, liquid chromatography/electrospray mass spectrometry (LC/ESI-MS) analysis for four different drugs (imipramine, desipramine, propranolol, and naproxen) that form inclusion complexes with CDs was performed in the presence and absence of beta-CD. These drugs are subject to nonspecific adsorption when brought into contact with plastics, such as HPLC tubing, sample collection and preparation apparatus, etc. Inclusion of the CD in the samples reduces this nonspecific adsorption due to competitive complex formation between the CD and the analyte. ESI-MS ion intensities increased when beta-CD was included in the sample with concentrations up to 1% (w:v), with a diverter valve installed post LC column. The degree of increased ion signal correlated with the beta-cyclodextrin:analyte binding constant. beta-CD appeared to elute within the void volume time and was observed in a full spectrum scan among the different analyte samples with up to 0.01% beta-CD injected directly to the LC/MS system with the diverter valve switched inline with the mass spectrometer. The use of the diverter valve allowed for direct injection of samples containing up to 1% beta-CD to the LC/MS without any deterioration of analyte ion signal.

Liquid-Phase Microextraction and Gas Chromatographic-Mass Spectrometric Analysis of Antidepressants in Vitreous Humor: Study of Matrix Effect of Human and Bovine Vitreous and Saline Solution.

In forensic bioanalytical methods, there is a general agreement that calibrators should be prepared by fortifying analytes in matrix-based blank samples (matrix-based). However, in the case of vitreous humor (VH), the collection of blank samples for the validation and for routine analysis would require the availability of many cadavers. Besides the difficulty of obtaining enough blank VH, this procedure could also represent an ethical issue. Here, a study of matrix effect was performed taking into consideration human and bovine vitreous and saline solution (SS) (NaCl 0.9%). Tricyclic antidepressants [amitriptyline (AMI), nortriptyline (NTR), imipramine (IMI) and desipramine (DES)] were used as model analytes and were extracted from samples by means of liquid-phase microextraction and detected by gas chromatography-mass spectrometry. Samples of human and bovine VH and SS were prepared in six different concentrations of antidepressants (5, 40, 80, 120, 160 and 200 ng/mL) and were analyzed. Relative matrix effect was evaluated by applying a two-tailed homoscedastic Student's t-test, comparing the results obtained with the set of data obtained with human VH and bovine VH and SS. No significant matrix effect was found for AMI and NTR in the three evaluated matrices. However, a great variability was observed for IMI and DES for all matrices. Once compatibilities among the matrices were demonstrated, the method was fully validated for AMI and NTR in SS. The method was applied to six VH samples deriving from real cases whose femoral whole blood (FWB) was analyzed by a previously published method. An average ratio (VH/FWB) of ∼ 0.1 was found for both compounds.

Photolysis of the antidepressants amisulpride and desipramine in wastewaters: Identification of transformation products formed and their fate.

Attenuation of pharmaceuticals due to natural sunlight is expected to be an important removal pathway in wastewater treatment plants using treatment lagoon systems. In this work, the photolysis of two antidepressants, amisulpride and desipramine, has been investigated in both ultrapure water and wastewater under simulated solar irradiation. Results showed that for amisulpride short irradiation times (t1/2 approximately 3h in pure water and 4h in wastewater) were adequate to degrade the parent compound while a longer exposure period was required for desipramine (t1/2 of approximately 36 h in pure water), although its degradation is enhanced almost three times by indirect photolysis in wastewaters. A significant number of transformation products (TPs) were identified for both pharmaceuticals by high-resolution mass spectrometry. In general, TPs formed are not persistent although acute toxicity tests for desipramine and its TPs showed an increase of the mixture toxicity after solar irradiation, suggesting that some TPs may be more toxic than the parent compound. In wastewaters collected from treatment lagoons, only amisulpride and one of its major TPs, TP 357, were detected. This indicates that long solar exposure times may be necessary for an effective elimination of these substances in lagoon systems or that photolysis may not be the main removal pathway for these particular compounds.

Desipramine and 2-hydroxydesipramine in human breast milk and the nursing infant's serum.

Desipramine and its metabolite 2-hydroxydesipramine were measured in the milk of a nursing mother and in the plasma of the mother and infant during administration of 300 mg/day of desipramine to the mother. Similar concentrations of both compounds were found in maternal plasma and milk. A pharmacokinetic plot of the milk over 24 hours showed the expected rise and fall of the substances following a single nighttime dose. Neither parent compound nor metabolite could be detected in the infant's serum even though the measurements were made shortly after peak ingestion by the infant. Furthermore, no clinical signs of toxicity were observed in the infant after 3 weeks of treating the mother with desipramine.

Measurement and pharmacokinetic analysis of imipramine and its metabolite by brain microdialysis.

1. The feasibility of the brain microdialysis method for direct measurement and pharmacokinetic study of imipramine (Imip) and its metabolite desipramine (DMI) was investigated in the rat brain. 2. A dialysis tube was inserted into the right striatum of male Wistar rats, which were administered i.p. with 12.5 mg kg-1 Imip. Thirty microliters dialysate was collected every 15 min, and the levels of Imip and DMI were measured by high-performance liquid chromatography with electrochemical detection (h.p.l.c.-e.c.d.). SKF-525A and aminopyrine were concomitantly administered in order to assess their respective effects on the pharmacokinetics of Imip and DMI in the brain. 3. The intracerebral half life (t1/2) of Imip was 2.4 +/- 0.3 h with Imip alone. Premedication with SKF-525A, an inhibitor of drug-metabolizing enzymes, significantly prolonged the t1/2 of Imip, while at the same time production of DMI from Imip was accordingly inhibited. Concomitant administration of aminopyrine did not induce any significant change in the concentrations of Imip, but significantly inhibited the concentrations of DMI through its competitive antagonism in the demethylation pathway. 4. The present results suggest that the brain microdialysis method reflects the intracerebral pharmacokinetics of Imip and DMI well and may be applicable to further pharmacokinetic investigations of psychotropic agents.

The effect of neuroleptics on imipramine demethylation in rat liver microsomes and imipramine and desipramine level in the rat brain.

A study of the cytochrome P-450 level and imipramine (IMI) demethylase activity in liver microsomes of rats treated concurrently with IMI and chlorpromazine (CPZ) or IMI and chlorprothixene (CPX) for two weeks were carried out. Concomitant administration of IMI and CPZ or IMI and CPX elevated the cytochrome P-450 level and accelerated IMI demethylation in in vitro study. Kinetic study of IMI demethylation carried out in the absence or in the presence of CPZ or CPX revealed that those neuroleptics inhibited IMI demethylation via competitive mechanism. Simultaneously with the enzymatic study the brain level of IMI and its demethylated metabolite desipramine (DMI) was assessed. It was found that 1 hr after withdrawal of IMI and CPZ or IMI and CPX the brain level of IMI was elevated in comparison with that of IMI treated animals, and the ratio between DMI/IMI brain concentration was decreased. When the assessment of IMI and DMI brain level was performed 24 hr after withdrawal of IMI and CPZ or IMI and CPX, there was no difference between the concentration of IMI and DMI in both, experimental and control animals.

Identification of misused drugs in the clinical laboratory. I. Tricyclics.

A systematic approach evaluating the abuse of tricyclic drugs in the hospital emergency room from the laboratory point of view is presented. This comprehensive screen involves qualitative colorimetric tests, ultraviolet (UV) spectrophotometry, thin layer chromatography (TLC), gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS). Laboratories with varying facilities and resources can adapt the present screen. Amitriptyline, doxepin, loxapine and desipramine misuse were identified and confirmed using the proposed methodology in 14 cases. Increasing misuse of tricyclic antidepressants requires that the clinical laboratory have a systematic approach to identify and confirm the presence of these drugs in emergency room patients.

Chronic treatment with imipramine: further functional evidence for the enhanced noradrenergic transmission in flexor reflex activity.

The chronic administration of imipramine (IMI; 10 mg/kg orally, twice daily for 14 days) enhanced the flexor reflex of the hind limb in the spinal rat. This effect was maintained for at least 72 h after termination of drug administration. Phenoxybenzamine but not cyproheptadine abolished the enhanced activity of the flexor reflex. After chronic administration of IMI high levels of desipramine (DMI) were found in the spinal cord, whereas IMI was not detectable there. No correlation was found between the levels of DMI in the spinal cord and the enhancement of the flexor reflex amplitude. A single i.v. dose of DMI facilitated the flexor reflex for a short period of time. In rats treated chronically with IMI, the binding of 3H-prazosin, a ligand of alpha 1-adrenoceptors, to spinal cord tissue was increased. The present results are a further argument for the previously advanced hypothesis that chronic administration of antidepressant drugs leads to an enhanced noradrenergic transmission, probably by increasing the number of alpha 1-adrenoceptors.

Impurities in drugs I: Imipramine, desipramine, and their formulations.

Nineteen lots of imipramine tablets and four lots of desipramine tablets were examined for impurities by TLC. Iminodibenzyl, desipramine, and 10,11-dihydro-5-[3-(methylamino-3'-dimethylaminopropyl)propyl]-5H-dibenz[b,f]azepine dihydrobromide (I) were found in some imipramine tablets, and iminodibenzyl and imipramine were found in some desipramine tablets, all at levels of less than 0.3% of label claim of the drug. Except for I, the identity of the impurities was established by comparison with known standards; I was synthesized and its composition was established by elemental analysis. All impurities, including I, were characterized by TLC, GLC, and mass spectrometry.

GLC method for iminodibenzyl and desipramine impurities in imipramine hydrochloride and its formulated products.

A GLC method is described for the determination of iminodibenzyl and desipramine impurities in imipramine hydrochloride and its formulated products. These impurities were extracted from an alkaline solution with a mixture of 30% methylene chloride in hexane for chromatography on a 3% OV-17 GLC column. Iminodibenzyl was determined using anthracene as an internal standard and desipramine was determined (after derivatization) using nortriptyline as an internal standard. Based on spiked excipient mixtures typically used to compound imipramine tablets, recoveries were 93-109% for iminodibenzyl and 93-107% for desipramine at 0.2-0.4% of the labeled claim of imipramine. Minimum detection levels were approximately 0.02% for each impurity, and procedural standards gave coefficients of variation of less than 1% for each impurity. The method was linear in the 0.05-0.5 microgram range and typically gave correlation coefficients greater than or equal to 0.999.

Non-aqueous capillary electrophoresis of drugs: properties and application of selected solvents.

The electrophoretic mobility of selected acidic and basic test solutes have been determined in non-aqueous media prepared by adding various combinations of ammonium acetate, sodium acetate, methane sulphonic acid and acetic acid to acetonitrile, propylene carbonate, methanol, formamide, N-methylformamide, N,N-dimethylformamide and dimethylsulphoxide, respectively. The apparent pH (pH*) of these non-aqueous media have been measured and it was found that pH* is an important factor for the separations in non-aqueous capillary electrophoresis. However, in some solvents the concentration of sodium acetate has a strong influence on the mobility despite very small changes in pH*. Due to the fact that a change in one parameter influences a number of other parameters it is very difficult to conduct systematic studies in non-aqueous media and to compare the migration of the species at fixed pH* values from one solvent to another. Thus pH* is only of value for comparison when used with a specific solvent or solvent mixture. The viscosity of the above-mentioned solvents were measured at various temperatures and means to adjust the viscosity of the non-aqueous media used for capillary electrophoresis are discussed and the separation of ibuprofen and its major metabolites in urine is used as an example.

Spectrophotometry assay of imipramine and desipramine using ammonium metavanadate and its application to pharmaceutical preparations.

Simple and sensitive method for determination of imipramine and desipramine is reported. The procedure is based on the oxidation of the drugs by ammonium metavanadate. Linear calibration graphs were obtained in the concentration range 0.6-40 microg ml(-1) of imipramine and 0.7-35 microg ml(-1) of desipramine with a relative standard deviation (RSD) less than 0.5%. The method was applied to the determination of the drugs in pharmaceutical preparations and compared favourably with independent official methods.

Plasma versus bone marrow desipramine: a comparative study.

Correlation between plasma and bone marrow tricyclic antidepressants has not been studied before. Two groups of rabbits were given 10 and 20 mg of desipramine/kg body weight, respectively. Desipramine was administered to the animals once daily by mouth for 5 days. On the fifth day the animals were sacrificed and blood and bone marrow samples were collected and analyzed using a high performance liquid chromatographic (HPLC) method. Data showed that a correlation exists between bone marrow and blood desipramine. The bone marrow desipramine concentration increased as its blood levels increased. The average ratio of bone marrow to blood desipramine +/- S.D. (standard deviation) in both dosage groups was 37.2 +/- 4.46 with a range of 30.99-44.82. This investigation is promising and shows that bone marrow could be used as an alternative tissue in the absence of a suitable blood sample.

Two tricyclic antidepressant poisonings: levels of amitriptyline, nortriptyline and desipramine in post-mortem biological samples.

Two deaths due to amitriptyline and desipramine overdoses are reported. The first case deals with a 20-year-old Caucasian male who was found dead at his residence. Toxicological analysis of the blood, urine, liver and kidney revealed the presence of amitriptyline (1.7 mg/l, 0.13 mg/l, 36.0 mg/kg and 98.0 mg/kg) and nortriptyline (0.66 mg/l, 0.74 mg/l, 12.0 mg/kg and 37.0 mg/kg). The gastric content contained only 220 mg of amitriptyline. The urine also contained norverapamil, which was consistent with previous verapamil therapy. The second case involved a 19-year-old Caucasian male who attempted suicide earlier and was on desipramine medication. The blood, urine, liver and gastric content disclosed the presence of desipramine in the concentrations of 14.2 mg/l, 33.7 mg/l, 112.5 mg/kg and 180 mg, respectively. The levels of these tricyclics analyzed by high pressure liquid chromatography were in agreement with the levels reported in the literature. Though with the amitriptyline poisoning no significant anatomic changes were noted, the desipramine-caused death was further supported by the multisystem vascular congestion and ischemic changes consistent with cardiopulmonary failure.