FeS2 nanosheets-luminol-O2 chemiluminescence method for determination of venlafaxine hydrochloride, imipramine hydrochloride, and cefazolin sodium

This study introduces a novel chemiluminescence (CL) approach utilizing FeS2 nanosheets (NSs) catalyzed luminol-O2 CL reaction for the measurement of three pharmaceuticals, namely venlafaxine hydrochloride (VFX), imipramine hydrochloride (IPM), and cefazolin sodium (CEF). The CL method involved the phenomenon of quenching induced by the pharmaceuticals in the CL reaction. To achieve the most quenching efficacy of the pharmaceuticals in the CL reaction, the concentrations of reactants comprising luminol, NaOH, and FeS2 NSs were optimized accordingly. The calibration curves demonstrated exceptional linearity within the concentration range spanning from 4.00 × 10-7 to 1.00 × 10-3 mol L-1, 1.00 × 10-7 to 1.00 × 10-4 mol L-1, and 4.00 × 10-6 to 2.00 × 10-4 mol L-1 with detection limits (3σ) of 3.54 × 10-7, 1.08 × 10-8, and 2.63 × 10-6 mol L-1 for VFX, IPM, and CEF, respectively. This study synthesized FeS2 NSs using a facile hydrothermal approach, and then the synthesized FeS2 NSs were subjected to a comprehensive characterization using a range of spectroscopic methods. The proposed CL method was effective in measuring the aforementioned pharmaceuticals in pharmaceutical formulations as well as different water samples. The mechanism of the CL system has been elucidated.

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.

Kinetic studies of drug-protein interactions by using peak profiling and high-performance affinity chromatography: examination of multi-site interactions of drugs with human serum albumin columns

Carbamazepine and imipramine are drugs that have significant binding to human serum albumin (HSA), the most abundant serum protein in blood and a common transport protein for many drugs in the body. Information on the kinetics of these drug interactions with HSA would be valuable in understanding the pharmacokinetic behavior of these drugs and could provide data that might lead to the creation of improved assays for these analytes in biological samples. In this report, an approach based on peak profiling was used with high-performance affinity chromatography to measure the dissociation rate constants for carbamazepine and imipramine with HSA. This approach compared the elution profiles for each drug and a non-retained species on an HSA column and control column over a board range of flow rates. Various approaches for the corrections of non-specific binding between these drugs and the support were considered and compared in this process. Dissociation rate constants of 1.7 (±0.2) s(-1) and 0.67 (±0.04) s(-1) at pH 7.4 and 37°C were estimated by this approach for HSA in its interactions with carbamazepine and imipramine, respectively. These results gave good agreement with rate constants that have determined by other methods or for similar solute interactions with HSA. The approach described in this report for kinetic studies is not limited to these particular drugs or HSA but can also be extended to other drugs and proteins.

Simultaneous determination of imipramine hydrochloride and chlordiazepoxide in pharmaceutical preparations by spectrophotometric, RP-HPLC, and HPTLC methods

A binary mixture of imipramine HCl and chlordiazepoxide was determined by three different methods. The first involved determination of imipramine HCl and chlordiazepoxide using the first derivative spectrophotometric technique at 219 and 231.5 nm over the concentration ranges of 1-20 and 2-24 microg/mL with mean accuracies of 99.47 +/- 0.78 and 101.43 +/- 1.20%, respectively. The second method utilized RP-HPLC with methanol-acetonitrile-0.065 M ammonium acetate buffer (45 + 25 + 30, v/v/v, pH adjusted to 5.6 +/- 0.02 with phosphoric acid) as the mobile phase pumped at a flow rate of 1.0 mL/min. Quantification was achieved using UV detection at 240 nm over concentration ranges of 0.25-4.0 and 0.1-1.6 microg/mL, with mean accuracies of 101.17 +/- 0.56 and 100.67 +/- 0.40% for imipramine HCl and chlordiazepoxide, respectively. The third method was HPTLC with carbon tetrachloride-acetone-triethylamine (pH 8.3; 6 + 3 + 0.3, v/v/v) as the mobile phase. Quantification was achieved with UV detection at 240 nm over concentration ranges of 50-600 and 20-240 ng/spot with mean accuracies of 99.51 +/- 0.59 and 100.59 +/- 0.84% for imipramine HCl and chlordiazepoxide, respectively. The suggested procedures were checked using prepared mixtures, and were successfully applied for the analysis of pharmaceutical preparations. The accuracy and precision of the methods were confirmed when the standard addition technique was applied. The results obtained by applying the proposed methods were statistically analyzed.

Screening and characterization of reactive metabolites using glutathione ethyl ester in combination with Q-trap mass spectrometry

The present study describes a new analytical approach for the detection and characterization of chemically reactive metabolites using glutathione ethyl ester (GSH-EE) as the trapping agent in combination with hybrid triple quadrupole linear ion trap mass spectrometry. Polarity switching was applied between a negative precursor ion (PI) survey scan and the positive enhanced product ion (EPI) scan. The negative PI scan step was carried out monitoring the anion at m/z 300, corresponding to deprotonated gamma-glutamyl-dehydroalanyl-glycine ethyl ester originating from the GSH-EE moiety. Samples resulting from incubations in the presence of GSH-EE were cleaned and concentrated by solid-phase extraction, followed by the PI-EPI analysis. Unambiguous identification of GSH-EE-trapped reactive metabolites was greatly facilitated by the unique survey scan of the anion at m/z 300, which achieved less background interference, in particular, from endogenous glutathione adducts present in human liver microsomes. Further structural characterization was achieved by analyzing positive MS(2) spectra that featured rich fragments without mass cutoff and were acquired in the same liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The effectiveness and reliability of this approach was evaluated using a number of model compounds in human liver microsomal incubations, including acetaminophen, amodiaquine, carbamazepine, 4-ethylphenol, imipramine and ticlopidine. In addition, iminoquinone reactive metabolites of mianserin were trapped and characterized for the first time using this method. Compared to neutral loss (NL) scanning assays using GSH as the trapping agent, the results have demonstrated superior selectivity, sensitivity, and reliability of this current approach.

Development of an HPLC method for the monitoring of tricyclic antidepressants in biofluids

A simple, rapid and sensitive HPLC method was developed and validated for the determination of four tricyclic antidepressants (TCAs): amitriptyline, doxepin, clomipramine (CLO) and imipramine, in pharmaceutical formulations and biological fluids. A Kromasil C(8 )analytical column (250 x 4 mm, 5 microm) was used for the separation, with a mobile phase consisting of 0.05 M CH(3)COONH(4) and CH(3)CN (45:55 v/v) delivered at 1.5 mL/min isocratically. Quantification was performed at 238 nm, with bromazepam (1.5 ng/microL) as the internal standard. The determination of TCAs in blood plasma was performed after protein precipitation. Urine analysis was performed by means of SPE using Lichrolut RP-18 Merck cartridges providing high absolute recoveries (> 94%). Direct analysis of urine was also performed after two-fold dilution. The developed method was fully validated in terms of selectivity, linearity, accuracy, precision, stability and sensitivity. Repeatability (n = 5) and between-day precision (n = 5) revealed RSD <13%. Recoveries from biological samples ranged from 91.0 to 114.0%. The absolute detection limit of the method was calculated as 0.1-0.6 ng in blood plasma and 0.2-0.5 ng in extracted urine or 0.4-0.7 in diluted urine. The method was applied to real samples of plasma from a patient under CLO treatment.

Comparative drug release studies of two cationic drugs from pH-responsive nanogels

pH-responsive nanogels consisting of methacrylic acid-ethyl acrylate (MAA-EA) cross-linked with di-allyl phthalate (DAP) were synthesized via the emulsion polymerization process. Delivery systems based on pH-responsive nanoparticles can control the release of rapidly metabolized drugs and/or have the ability to protect sensitive drugs, thereby making them ideal candidates for drug delivery applications. In this study, a drug selective electrode (DSE) was used to directly measure the concentration of procaine hydrochloride (PrHy) and imipramine hydrochloride (IMI) released from MAA-EA nanogels. With a single drug delivery system, drug release for two different drugs loaded via two distinctly different interaction forces was demonstrated. Drug release was conducted using the DSE under different pHs, MAA-EA molar ratio and DAP content. The release rate increased with pH for PrHy loaded nanogels and MAA-EA molar ratio but decreased with pH for IMI loaded nanogels and DAP content. PrHy was found to be hydrophobically bounded, while IMI was found to be electrostatically bounded onto the MAA-EA nanogels, which was further enhanced by hydrogen bonding.

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.

A liquid chromatographic method using a reversed-phase hybrid stationary phase to control potential impurities of imipramine hydrochloride

A reversed-phase liquid chromatographic method has been developed for the detection and control of impurities of imipramine hydrochloride at a level of 0.2 microg/ml (corresponding to 0.02 per cent in the procedure described). This method is included in a proposed revision of the monograph (Pharmeuropa 18.4) and replaces the thin-layer chromatographic method currently employed.

Coupling on-chip solid-phase extraction to electrospray mass spectrometry through an integrated electrospray tip

We report the integration of solid-phase extraction (SPE) with mass spectrometry (MS) through an on-chip electrospray tip for sample precleaning and preconcentration. An in situ polymerized alkylacrylate-based monolithic column was used as the stationary phase for the on-chip SPE. Each microchip consists of two sets of microchannels and their respective integrated electrospray tips, with a common gold electrode. After the microchip was fabricated from cycloolefin polymer by hot embossing, thermal bonding, and annealing steps, a mixture of monomers and porogenic solvents was pumped into the microchannels and certain areas of the main microchannels were exposed to UV irradiation through a mask. The resulting porous monolithic beds that were polymerized from different compositions of the mixture were characterized by scanning electron microscopy. The microchip containing the monolithic column was then interfaced to an ion trap (IT) mass spectrometer by modifying a commercially available interfacing system. Makeup solution from the side channel was infused concurrently with the solution flowing into the main channel, and the mixture of these two solutions was sprayed into the MS orifice. Both the adsorption and elution of a pharmaceutical test compound, imipramine, to and from the on-chip SPE columns were monitored by MS. The potential application of this device for sample cleanup was demonstrated by pretreatment of urine samples spiked with imipramine.

High-Throughput Solution-Based Medicinal Library Screening against Human Serum Albumin

High-throughput screening of combinatorial libraries has evolved from studying large diverse libraries to analyzing small, structurally similar, focused libraries. This paradigm shift has generated a need for rapid screening technologies to screen both diverse and focused libraries in a simple, efficient, and inexpensive manner. We have proactively addressed these needs by developing a high-throughput, solution-based method combining size exclusion (SEC), two-dimensional liquid chromatography (2-D LC), and mass spectrometry (MS) for determining the relative binding of drug candidates in small, focused medicinal libraries against human serum albumin (HSA). Two types of libraries were used to evaluate the performance of the system. The first consisted of five diverse ligands with a wide range of hydrophobicities and whose association constants to HSA cover 3 orders of magnitude. A beta-lactam library composed of structurally similar compounds was used to further confirm the validity of the methodology. The ability to distinguish site-specific interactions of drugs competing for individual domains of the HSA receptor is also demonstrated. Comparison of chromatographic profiles of the library components before and after incubation with the receptor using multiple reaction monitoring allowed a ranking of the ligands according to their relative binding affinities. The observed rankings correlate closely with literature values of the association constants between the respective ligands and HSA. This simple, rugged methodology can screen a wide spectrum of chemical entities from combinatorial mixtures in less than 6 min.

Application of two chemometric methods for the determination of imipramine, amitriptyline and perphenazine in content uniformity and drug dissolution studies

Double-divisor spectra derivative and partial least squares methods were developed for content uniformity and dissolution tests in binary or ternary mixtures. The simultaneous determinations of perphenazine (PER) combined with amitriptyline hydrochloride (AMI) and/or imipramine hydrochloride (IMI) have been accomplished using the information of the absorption spectra of appropriate solutions. The double-divisor method is based on the use of the first derivative of the ratio spectrum obtained by dividing the absorption spectrum of the ternary mixture PER-AMI-IMI by a standard spectrum resulted from the addition of two of the three analytes in equal concentrations. The concentration of each component is then determined from their respective calibration graphs established by measuring the ratio derivative analytical signal at a specific wavelength. In this method, the linear determination ranges were of 3.65-18.24 microg/mL for PER, 4.32-21.60 microg/mL for AMI, and 4.83-24.19 microg/mL for IMI. The results were compared with those obtained by partial least squares multivariate calibration (PLS) method pre-treated by a wavelet compression-orthogonal signal correction (W-OSC) filter in zero-order derivative spectra. The calibration model was evaluated by internal validation (cross-validation) and by external validation over synthetic mixtures, content uniformity and dissolution tests. According to the dissolution profile test more than 95% of the three substances were dissolved within 10 min. The results from both techniques were statistically compared with each other and can be satisfactorily used for quantitative analysis and dissolution tests of multicomponent tablets.

2,2'-Bipyridine as a new and sensitive spectrophotometric reagent for the determination of nanoamounts of certain dibenzazepine class of tricyclic antidepressant drugs

2,2'-bipyridine is proposed as new and sensitive spectrophotometric reagent for the determination of certain dibenzazepine class of tricyclic antidepressants. The spectrophotometric method is based on the reaction of imipramine hydrochloride (IPH), desipramine hydrochloride (DPH), clomipramine hydrochloride (CPH), trimipramine maleate (TPM) and opipramol (OPP) with iron (III) and subsequent reaction with 2,2'-bipyridine in an acetic acid medium to yield a pink color with maximum absorption at 530 nm. The color developed was stable over 3-4 h at room temperature (approximately 27 degrees C). The commonly encountered excipients and additives did not interfere with the determination. Results from the analysis of pure drugs and commercial tablets agreed well with those of the official method (United States Pharmacopoeia, 24, USP Convention, Rockville 2000, pp. 505-506, 865-867.).

Determination of imipramine in presence of iminodibenzyl and in pharmaceutical dosage form

Two spectrophotometric methods for the determination of imipramine in presence of iminodibenzyl as an impurity are described. The first method is a ratio-spectra first derivative spectrophotometry, the signals were measured at 240.2 nm for imipramine. Calibration graph was found linear in the range 5-30 microg ml(-1). The second method is based on the reaction of imipramine base, being an electron donor, with p-chloranilic acid, being pi acceptor, to form a purple colored charge transfer complex. The absorbance was measured at 520.5 nm without interference with iminodibenzyl. Both methods are rapid, simple and do not require any preliminary separation or treatment of the samples. Furthermore, the two methods were applied to pharmaceutical dosage form.

An electrospray ionization source for integration with microfluidics

We have demonstrated a new electrospray ionization (ESI) device incorporating a tip made from a shaped thin film, bonded to a microfluidic channel, and interfaced to a time-of-flight mass spectrometer (TOFMS). A triangular-shaped thin polymer tip was formed by lithography and etching. A microfluidic channel, 20 microm wide and 10 microm deep, was embossed in a cyclo olefin substrate using a silicon master. The triangular tip was aligned with the channel and bonded between the channel plate and a flat plate to create a microfluidic channel with a wicking tip protruding from the end. This structure aided the formation of a stable Taylor cone at the apex of the tip, forming an electrospray ionization source. This source was tested by spraying several solutions for mass spectrometric analysis. Because the components are all made by lithographic approaches with high geometrical fidelity, an integrated array system with multiple channels can be formed with the same method and ease as a single channel. We tested a multichannel system in a multiplexed manner and showed reliable operation with no significant cross contamination between closely spaced channels.

Studies and analytical application of reaction of imipramine with chrome azurol S

Chrome azurol S (CAS) was tested as a spectrophotometric reagent for the determination of imipramine (IMP). It reacts in aqueous media with IMP forming pink-red, sparingly soluble in water ion association compound. This compound was quantitatively extracted with chloroform and the absorbance of organic phase was measured at 510 nm. The extraction conditions were studied using a batch method. On the basis of the results obtained with batch method, three-line flow-injection system was constructed. Batch and flow-injection methods were successfully applied for the determination of IMP in pharmaceutical preparation.

Simultaneous LC determination of some antidepressants combined with neuroleptics

A reversed-phase HPLC method with UV detection at 252 nm is presented for the simultaneous determination of some tricyclic antidepressants (amitriptyline, imipramine) and neuroleptics (chlorprothixene, thioridazine) in their quaternary mixtures. Sample analysis was performed on a bonded reversed phase C-18, 5 microm, 250 x 4.6 mm ID (Lichrospher 100RP-18) column using acetonitrile and 0.01 M aqueous solution of triethylamine (1:1) as the mobile phase at 0.9 ml/min. The pH was adjusted to 2.7 with concentrated phosphoric acid. The retention time was for imipramine, amitriptyline, chlorprothixene, and thioridazine 5.8, 6.5, 8.3, 10.8 min, respectively. The linearity was obeyed up to 15 ppm for imipramine and amitriptyline, 12 ppm for chlorprothixene and 10 ppm for thioridazine. The presented method also allows the determination of the mentioned drugs individually in their pharmaceutical preparations.

Spectrophotometric studies and application of imipramine-eriochrome cyanine R system for determination of imipramine in pharmaceuticals

Eriochrome cyanine R (ECR) has been tested as reagent for the determination of imipramine. It reacts in neutral medium with imipramine forming reddish compound, which can be quantitatively extracted into n-butanol. This property has been successfully used for the extractive-spectrophotometric determination of imipramine. Beer's law is obeyed in concentration range of 10-80 microg ml(-1) of imipramine. The method was applied to the determination of imipramine in its pharmaceutical.

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.

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.

Nonaqueous capillary electrophoretic separation and thermo-optical absorbance detection of five tricyclic antidepressants and metabolism of amitriptyline by Cunninghamella elegans

We developed a technique based on nonaqueous capillary electrophoresis and laser-based thermo-optical absorbance detection to assay five antidepressants with similar structures and mass-to-charge ratios. A mixture of methanol and acetonitrile with ammonium acetate was essential to achieve baseline resolution of these compounds. We investigated the effects of ammonium acetate concentration, temperature, applied voltage, and capillary length on separation efficiency. The nonaqueous capillary electrophoresis and laser-based thermo-optical absorbance detection technique was used to study the metabolism of amitriptyline by Cunninghamella elegans. Sample preparation procedures were simplified for fast screening of the parent drug and its metabolites. Reproducible electropherograms were obtained from replicate cultures of C. elegans growing in the presence of amitriptyline.

On-line nonaqueous capillary electrophoresis and electrospray mass spectrometry of tricyclic antidepressants and metabolic profiling of amitriptyline by Cunninghamella elegans

An on-line nonaqueous capillary electrophoresis-electrospray mass spectrometry (ESI-MS) technique was developed using a commercial ion spray interface. The nonaqueous capillary electrophoresis ESI-MS system was used to profile tricyclic antidepressants of similar structures and mass-to-charge ratios. We found that pure methanol can be used as a sheath liquid to obtain stable ion spray from nonaqueous capillary electrophoresis. The flow rate of the coaxial nebulizing gas affected baseline signals, separation efficiency, and migration times. Other nonaqueous capillary electrophoresis operating conditions and electrospray parameters were optimized for enhanced baseline separation and high sensitivity detection. The effect of sample stacking on separation and detection was evaluated. The calculated detection limits were approximately 3 pg injected onto the capillary. ESI mass spectra of tricyclic antidepressants from a single quadrupole MS were obtained and elucidated. The information was used to propose fragmentation pathways of the tricyclic antidepressants. The method was also used to analyze the metabolites of amitriptyline produced by the fungus Cunninghamella elegans. Sixteen metabolites were detected and most of them were tentatively identified as demethylated and/or hydroxylated, and/or N-oxidized products.

Stability of tricyclic antidepressants in formalin solutions

We investigated the stability of the secondary amines, desipramine (DP) and nortriptyline (NRT), and the tertiary amines, imipramine (IP) and amitriptyline (AT), in formaldehyde (F) and paraformaldehyde (PF) aqueous solutions. NRT showed little instability in 0.37 to 37% F and PF solutions, but AT formation was detected and increased, up to 0.46 to 2.7%, in parallel with rising F and PF concentrations. DP was unstable and levels decreased to 74 to 96% with increasing F concentrations, and fell only to 96% in 10% PF solution. IP formation increased in the same manner as AT to 2.9 to 3.5% of the initial DP. When AT and IP were stored in F and PF solutions, concentrations of AT and IP did not change. DP in F pH 3 to 11 phosphate buffer (PB) solutions showed high recovery in the order: pH 5 > pH 7 > pH 9 > pH 3 and pH 11. DP in PF buffered solutions decreased slightly only at pH 3 (3.5%). By contrast, IP did not change at any pH (pH 3 to 11) of the F or PF solutions. During storage for 21 days at room temperature in 3.7% F and PF solutions, IP and DP degradation was accelerated when compared with the values in pH 3 and 7 PB solutions. However, IP detected in DP F or PF solution was only 0.2% of the initial DP 21 days after storage. Thus, AT, NRT, IP and DP degraded gradually in F and PF solutions during storage at room temperature. TCAs may first react nucleophilically with formaldehyde to form hemiaminals. DP in 3.7% formaldehyde aqueous solution formed little of its methylated product, IP, at room temperature.

On-line capillary electrophoresis-electrospray ionization mass spectrometry using a polymerized anionic surfactant

On-line capillary electrophoresis-electrospray ionization-mass spectrometry (CE-ESI-MS) has been used to determine the tricyclic antidepressant drugs (imipramine, doxepin, and amitriptyline) as well as the beta-adrenergic blocker drugs (propranolol and alprenolol). A CE-ESI-MS interface linking a manually operated CE system and a Finnigan MAT-900 sector mass spectrometer (with an Analytica electrospray ionization source) has been constructed in-house and employed for this study. Although a water/methanol based capillary zone electrophoresis (CZE) buffer was initially used to determine these analytes, enhanced resolution was obtained by addition of a polymerized surfactant, i.e., poly-sodium undecylenic sulfate (poly-SUS), into the electrokinetic chromatography (EKC) buffer. When a low concentration of this poly-SUS surfactant was added to a volatile EKC buffer, these structurally similar cationic drugs were EKC separated and on-line detected by ESI-MS.

Sensitive microanalysis of imipramine and desipramine in single rat thyroids by gas chromatography-mass spectrometry

A new sensitive method for the quantitative determination of imipramine and desipramine in single rat thyroids using gas chromatography-mass spectrometry with selected ion monitoring, after enzymatic hydrolysis and liquid-liquid extraction has been developed. The technique was deemed suitable for microanalysis of single rat thyroids and for other solid tissues, using smaller sample sizes than usually required for traditional determination methods. The quantification was linear from 10 to 200 nmol/l (i.e., from 0.25 to 5 microg/g) for imipramine and from 100 nmol/l to 2000 nmol/l (i.e., from 2.4 to 47 microg/g) for desipramine, and the limits of detection (less than 25 ng/g tissue for both compounds) were better than those previously reported. Recoveries, repeatability and reproducibility of this technique were satisfactory. It has been successfully applied in a preliminary study of the concentration-time profiles of imipramine and desipramine in the thyroid of rats treated with either of these drugs.

Voltammetric determination of imipramine hydrochloride and amitriptyline hydrochloride using a polymer-modified carbon paste electrode

In this paper the voltammetric behaviors of imipramine.HCl and amitriptyline. HCl, which are both tricyclic antidepressants, were investigated using a carbon paste electrode, modified by the addition of poly(N-vinylimidazole), in various solutions of different pHs. It was shown that the current density for imipramine increased with modification of the carbon paste electrode and amitriptyline, which was electroinactive with the normal carbon paste electrode, became electroactive on the modified electrode. The optimum conditions for the quantitive determination of imipramine.HCl and amitriptyline.HCl were determined and statistical analysis of the linear relationship between current and concentration is given. The method was applied for the determination of these substances in the pharmaceutical dosage forms.

High-performance liquid chromatographic method for the analysis of imipramine metabolism in vitro by liver and brain microsomes

A new sensitive method for resolution and quantitation metabolites of in vitro imipramine metabolism has been developed for use in liver and brain microsomes. Separation of metabolites was done using a Supelcosil PCN column with a mobile phase of acetonitrile-methanol-potassium phosphate dibasic (40:35:25, v/v/v), pH 7. Resolution is achieved for 2- and 10-hydroxyimipramine, and desipramine. Varying levels of these metabolites formed during in vitro incubations of rat liver and brain microsomes following treatments.

Second-order derivative spectrophotometric assay for imipramine hydrochloride and diazepam in pure admixtures and in dosage forms

The determination of imipramine HCl and diazepam in tablets by derivative spectrophotometry is described. The drugs in combined preparations have been quantified using the second-order derivative spectra of their solutions in 0.1 M HCl. The method has been applied to pure drug mixtures as well as commercial preparations and was found to be precise and reproducible. Compliance of Beer's Law was observed in the concentration range of 10-70 micrograms ml-1 for imipramine HCl and 2-8 micrograms ml-1 for diazepam. Lower limits of detection at the 95% confidence level were 1.96 micrograms ml-1 for imipramine HCl and 0.21 microgram ml-1 for diazepam.

Rapid microsample analysis of imipramine and desipramine by reversed-phase high-performance liquid chromatography with ultraviolet detection

A rapid and highly sensitive HPLC assay method was developed to measure small amounts of imipramine and its major metabolite, desipramine. The assay involved simple extraction procedures using clomipramine as the internal standard. The mobile phase consisted of acetonitrile (60%) and 0.01 M triethylamine in distilled water (40%) with the pH adjusted to 3.0. Separations were achieved on a C18 column and the effluent measured for UV absorption at 260 nm. The chromatographic separation was excellent, with no interference from endogenous serum constituents. This assay was suitable for measuring drug concentrations in the range of 10-1000 ng/ml using a 0.1-ml serum sample. The method was applied to a drug disposition study in transgenic mice with increased plasma alpha 1-acid glycoprotein.

Seasonal rhythm of platelet [3H]imipramine binding in adolescents who attempted suicide

OBJECTIVE

This study was designed to determine the seasonality of serotonin functions among adolescents who attempt suicide.

METHOD

Platelet [3H]imipramine binding was assessed over a period of 18 months in 98 adolescents who attempted suicide and a comparison group of 23 never-suicidal youths with conduct disorder.

RESULTS

[3H]Imipramine (Bmax) was uncorrelated with age, but showed considerable seasonal variability over time in those who had attempted suicide.

CONCLUSIONS

[3H]Imipramine binding density in adolescents who attempted suicide exhibited significant seasonality, reaching a nadir in late winter/early spring.

Immunoassay reagents for psychoactive drugs. Part 5. Quantitative determination of imipramine and desipramine by fluorescence polarization immunoassay

Two methods for the quantitative determination of imipramine (IMI) and desipramine (DMI) by fluorescence polarization immunoassay (FPIA) are described. One immunoassay allows for the accurate quantification of imipramine in the presence of desipramine, while the other allows for the accurate quantification of desipramine in the presence of imipramine.

The study of tricyclic antidepressants in formalin-fixed human liver and formalin solutions

The stability of amitriptyline, nortriptyline, desipramine and imipramine in formalin-fixed human liver tissue and formalin solutions was investigated. The levels of the tricyclic and its primary demethylated metabolite in the frozen liver were determined and compared with levels obtained in the formalin-fixed liver and formalin solutions in which the liver was stored. It was obvious that some methylation of the secondary amine, nortriptyline, to the corresponding tertiary amine, amitriptyline, and of desipramine to imipramine took place in the formalin environment. Nortriptyline was not detected in most cases, suggesting that it may degrade more rapidly than desipramine. There was no consistent ratio between the concentration of the drug in the frozen liver tissue versus formalin-preserved tissue or versus formalin solution. The methylation rates of the secondary amines could not be quantitated. Storage of the liver tissue in formalin at room temperature resulted in leaching of the drugs into the formalin solution. The drugs tested may be detected for up to 22 months in the formalin-fixed liver and in the formalin medium.

Metabolism of imipramine in vitro by isozyme CYP2D6 expressed in a human cell line, and observations on metabolite stability

A metabolism study of imipramine (IMI) has been conducted in vitro with commercially available human CYP2D6 isozyme expressed in a human AHH-1 TK +/- cell line. This enzyme system catalyzed the anticipated ring-oxidative biotransformation of IMI to 2-hydroxyimipramine (2-OH-IMI). In addition, however, the human CYP2D6 isozyme preparation was found to be unequivocally involved in the N-dealkylation of IMI to desmethylimipramine (DMI). 2-Hydroxydesipramine was also identified as a trace metabolite of IMI, but no 10-hydroxyimipramine was detected. The 2-OH-IMI metabolite was unstable and disappeared from metabolic solutions on standing. A procedure involving the O-acetylation of 2-OH-IMI was developed to minimize this decomposition. When an authentic sample of 10-OH-IMI was subjected to the same acetylation procedure, it was partially dehydrated to 10,11-dehydroimipramine, but also underwent unexpected degradations to two other products in which the dimethylaminopropyl side-chain was deaminated. Plausible structures for these two decomposition products are suggested from their gas chromatographic-mass spectrometric behaviour.

High-performance liquid chromatography of imipramine and six metabolites in human plasma and urine

A method for the simultaneous quantitation of imipramine and six metabolites (2- and 10-hydroxyimipramine, 2- and 10-hydroxydesipramine, didesmethylimipramine and desipramine) in human plasma and urine has been developed. The method is based on a three-step liquid-liquid extraction followed by isocratic, reversed-phase high-performance liquid chromatography with ultraviolet absorbance detection (detection wavelength: 220 nm). The chromatographic eluent consisted of 30% acetonitrile and 70% aqueous sodium perchlorate solution pH 2.5. Glucuronide conjugates in urine were deconjugated with beta-glucuronidase/arylsulphatase prior to extraction.

Simultaneous determination of imipramine and amitryptiline by derivative spectrophotometry

Three methods are proposed for the simultaneous determination of imipramine and amitryptiline by derivative spectrophotometry, one of them using both first- and second-derivative spectra, and the others using the first- and second-derivative spectra, respectively, obtained from a "diode array" spectrophotometer. The methods allow the determination of 0.62-10.14 micrograms ml-1 of imipramine, and 0.63-10.04 micrograms ml-1 of amitryptiline, and have been applied to their determination in blood serum.

[A chemical-toxicological analysis of combined poisonings by psychotropic preparations with a tricyclic structure]

Conditions for chromatographic separation of melipramine with aminazine and melipramine with amitriptyline mixtures were stated. Method of chemical toxicological analysis in combined poisonings with psychotropic agents of tricyclic structure (melipramine in combinations with amitriptyline and aminazine) was suggested. Method was tested experimentally using animals.

A SepPak HPLC method for tricyclic antidepressant drugs in human vitreous humor

Death from tricyclic antidepressant overdose has become an all-too-common occurrence. Several factors, including postmortem concentration changes, can render blood and tissue samples useless for the determination of antidepressant drug concentrations. We present here an efficient method of solid-phase extraction for these drugs from vitreous humor and a reversed-phase, isocratic high-performance liquid chromatographic method for the simultaneous quantitation of amitriptyline, doxepin, and imipramine and their desmethylated metabolites.

Autoradiographic analysis of tritiated imipramine binding in the human brain post mortem: effects of suicide

In vitro quantitative autoradiography of high-affinity tritiated imipramine binding sites was performed on brains of 12 suicide victims and 12 matched controls. Region-specific differences in imipramine binding were found between the two groups. Thus, the pyramidal and molecular layers of the cornu ammoni hippocampal fields and the hilus of the dentate gyrus exhibited 80%, 60%, and 90% increases in binding in the suicide group, respectively. The postcentral cortical gyrus, insular cortex, and claustrum had 45%, 28%, and 75% decreases in binding in the suicide group, respectively. No difference in imipramine binding was observed in prefrontal cortical regions, in the basal ganglia, and in mesencephalic nuclei. No sex and postmortem delay effects on imipramine binding were found. Imipramine binding was positively correlated with age, the effect of age being most pronounced in portions of the basal ganglia and temporal cortex.

Simultaneous determination of imipramine, desipramine and their deuterium-labelled analogues in biological fluids by capillary gas chromatography-mass spectrometry

A specific, sensitive and accurate method for the determination of imipramine, desipramine and their d4 analogues in biological fluids using d8 analogues as internal standards using capillary gas chromatography-chemical ionization mass spectrometry was developed. Drug concentrations were measured by selected-ion monitoring of the quasi-molecular ions of imipramine and the trifluoro-acetyl derivative of desipramine. The coefficient of variation and relative error at a concentration of about 2 ng/ml in plasma were found less than 10% and 7%, respectively, for both drugs. No isotope effect was observed following the oral administration of an equimolar mixture of imipramine and [2H4]imipramine to a rat.

Analysis of 2-hydroxyimipramine in an imipramine-related fatality

A fatality following ingestion of the tricyclic antidepressant imipramine (Novopramine), acetaminophen, and ethyl alcohol is described. Imipramine, desipramine, acetaminophen, and 2-hydroxyimipramine were quantitated by high performance liquid chromatography, and ethyl alcohol by gas liquid chromatography. Concentrations of imipramine, desipramine, 2-hydroxyimipramine, and acetaminophen were: in blood--9.0, 1.1, 3.9, and 11 mg/L; in urine--92, 14, and 42 mg/L (acetaminophen not quantitated in urine). Ethyl alcohol concentration in blood was less than 10 mg/dL and 105 mg/dL in the urine by headspace gas chromatography. These findings are compared to previous reports of imipramine-related fatalities. To our knowledge, this is the first fatality reported involving imipramine where analysis included quantitation of 2-hydroxyimipramine in blood and urine.

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.

Quantitative homogeneous enzyme immunoassays for amitriptyline, nortriptyline, imipramine, and desipramine

We describe specific EMIT homogeneous enzyme immunoassays for amitriptyline, nortriptyline, imipramine, and desipramine in patients' serum samples. Before analysis, an easily performed extraction step involving the use of 500 microL of sample and a 1-mL disposable column eliminates cross-reacting polar metabolites. The range of the standard curve for the first three drugs is 25 to 250 micrograms/L, and for desipramine is 50 to 500 micrograms/L. Within-run and between-run CVs are less than 10% throughout the range of the assays. Results for patients' samples obtained by this method and by "high-performance" liquid chromatography compare well, showing a slope range of 0.94-1.04 and correlation coefficients ranging from 0.93 to 0.96, depending on the assay.

A sensitive colorimetric method for the determination of imipramine hydrochloride and desipramine hydrochloride

A simple and rapid colorimetric method for the determination of imipramine hydrochloride and desipramine hydrochloride in their tablet formulations and in biological fluids is presented. The method is based on the reaction of these drugs with 3-methyl-2-benzothiazolone hydrazone in the presence of ferric chloride, with direct measurement at 635 nm. Cyclohexane was used to extract these drugs from serum and urine, at basic pH, by a single manual extraction. The method can detect 0.5 microgram/ml of each drug. The main advantages of this method are its simplicity and high sensitivity.

Demonstration of endogenous "imipramine like" material in rat brain

The extraction and partial purification of an endogenous "imipramine- like" material from rat brain is described. The endogenous factor obtained after gel filtration and silica chromatography inhibits [3H] imipramine specific binding and mimics the inhibitory effect of imipramine on [3H] serotonin uptake in both brain and platelet preparations. The effects of the endogenous material are dose-dependent and it inhibits [3H] imipramine binding in a competitive fashion. The factor is unevenly distributed in the brain with high concentration in the hypothalamus and low concentration in the cerebellum.

The analysis and disposition of imipramine and its active metabolites in man

Single oral and intramuscular (i.m.) doses of imipramine (IMI) were administered to four normal males. Serum and urine concentrations of IMI, desipramine (DMI) and their unconjugated 2-hydroxy metabolites were measured by high-pressure liquid chromatography (HPLC). Urinary conjugated 2-hydroxy metabolites were also measured after enzyme hydrolysis. Computer analysis of serum concentration and urinary excretion rate data allowed confirmation of drug and metabolite kinetics, and calculation of pharmacokinetic parameters. The rapid appearance of the metabolites in serum indicates that sequential first-pass metabolism of IMI involves both hydroxylation and demethylation. However, the dose-normalized areas under the serum concentration-time curves indicate that the fractions of the doses converted to metabolites were similar after both routes of IMI administration. Similar total fractions of the i.m. and oral doses recovered in urine indicate complete absorption of the oral doses. Inclusion of the metabolites increased the apparent availability of active components after oral IMI from 22%-50% to 45%-94%. Both the 2-hydroxy metabolites exhibited formation rate-limited kinetics, whereas DMI kinetics were elimination rate-limited. The t1/2 of IMI and 2-hydroxyimipramine (2-OH-IMI) was 6-18 h, while that of DMI and 2- hydroxydesipramine (2-OH-DMI) was 12-36 h. The t1/2 of these compounds was 1.5-2 times longer after the i.m. doses. The metabolite/parent ratios and the disposition of the individual metabolites confirm findings that chronic dosing results in only limited accumulation of hydroxy metabolites.

Thin-layer chromatographic determination of imipramine and desipramine in human plasma and urine at single-dose levels

Thin-layer chromatographic methods were up-dated for pharmacokinetic studies of imipramine in plasma and urine. The free parent compound and its free desmethyl metabolite desipramine are determined in plasma. Conjugates of both compounds in urine are cleaved on treatment with glucuronidase/arylsulfatase. Following chromatography, intense yellow derivatives are obtained overnight on standing or by exposure to nitrous gases. Detection is performed in the visible range at 405 nm (plasma) or 460 nm (urine). The methods are selective, accurate and sensitive, with detection limits for plasma of 2 ng/ml imipramine--HCl and 2 ng/ml desipramine--HCl, and 0.06 micrograms/ml total imipramine--HCl and 0.126 micrograms/ml total desipramine--HCl for urine. Pharmacokinetic data from plasma and urine results following single oral doses of 50 mg imipramine--HCl to eight volunteers were computed using one-compartment open models.