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Drug Metabolites (drug + metabolite)
Selected AbstractsA new type of minocycline-induced cutaneous hyperpigmentationCLINICAL & EXPERIMENTAL DERMATOLOGY, Issue 1 2004R. W. Mouton Summary Pigmentary disorders are recognized adverse effects of the semi-synthetic tetracycline derivative antibiotic, minocycline. Three distinct types of minocycline-induced cutaneous pigmentation have been described. Type I, blue,black pigmentation confined to sites of scarring or inflammation on the face; Type II, blue,grey circumscribed pigmentation of normal skin of the lower legs and forearms; and Type III, diffuse muddy brown pigmentation of normal skin accentuated in sun-exposed areas. We report two patients with acne vulgaris with a fourth type of minocycline-induced cutaneous pigmentation. They presented with circumscribed blue,grey pigmentation within acne scars confined to the back. Histology showed pigment within dendritic cells, and extracellularly throughout the dermis. Histochemistry identified a calcium containing melanin-like substance. Iron was absent. Immunohistochemistry confirmed some pigment-containing cells to be macrophages. Electron microscopy demonstrated electron-dense granules, free and membrane-bound, within macrophages and fibroblast-like cells. Energy-dispersive X-ray analysis confirmed the presence of calcium. Iron was absent. This fourth type of cutaneous minocycline hyperpigmentation may be a variant of Type I, but based on clinical, pathological and microanalytical differences, appears to be a new entity. The pigment may be a drug metabolite,protein complex chelated with calcium, or an insoluble minocycline,melanin complex. We propose a classification of cutaneous minocycline pigmentation based on clinico-pathological criteria. [source] Identification of diphenhydramine metabolites in human urine by capillary electrophoresis-ion trap-mass spectrometryELECTROPHORESIS, Issue 10-11 2004Andrea Baldacci Abstract The identification of diphenhydramine (DH) metabolites that are frequently observed in the capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MEKC) analyses of alkaline liquid/liquid and solid-phase extracts of patient urines is demonstrated. Having standards for DH and diphenhydramine- N -oxide (DHNO), the presence of these two compounds could be confirmed in urines that were collected overnight after administration of 25 mg DH chloride. Using CZE coupled to ion-trap mass spectrometry (CE-MSn) with positive electrospray ionization and an acetate buffer at pH 5.6, the [M+H]+ ions of DH (m/z = 256), DHNO (m/z = 272), and nordiphenhydramine (NDH, m/z = 242) and their fragmentation to a common m/z 167 product ion (diphenylcarbinol moiety) was monitored. The data indicate that all three compounds are cations in an acidic environment, the migration order being NDH, DH, and DHNO. Data obtained under negative electrospray ionization conditions suggest the presence of diphenylmethoxyacetic acid-glycine amide ([M-H], ion of m/z 298 and fragmentation to m/z 254, loss of CO2), a metabolite that could tentatively be assigned to a characteristic peak observed in the MEKC electropherogram at alkaline pH. The data presented in this paper illustrate the value of using CE-MSn for identification of urinary drug metabolites for which no standards are available. [source] A Diversified Library of Bacterial and Fungal Bifunctional Cytochrome P450 Enzymes for Drug Metabolite SynthesisADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2009Roland Weis Abstract Innovative biohydroxylation catalysts for the preparation of drug metabolites were developed from scratch. A set of bacterial and fungal sequences of putative and already known bifunctional P450 enzymes was identified by protein sequence alignments, expressed in Escherichia coli and characterised. Notably, a fungal self-sufficient cytochrome P450 (CYP) from Aspergillus fumigatus turned out to be especially stable during catalyst preparation and application and also in presence of organic co-solvents. To enhance the catalytic activity and broaden the substrate specificity of those variants with high expression levels prominent single mutations were introduced. Selected improved variants were then used as lyophilised bacterial lysates for the synthesis of 4,-hydroxydiclofenac and 6-hydroxychlorzoxazone, the two metabolites of active pharmaceutical compounds diclofenac and chlorzoxazone representing the same metabolites as generated by human P450s. [source] Mass defect filter technique and its applications to drug metabolite identification by high-resolution mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 7 2009Haiying Zhang Abstract Identification of drug metabolites by liquid chromatography/mass spectrometry (LC/MS) involves metabolite detection in biological matrixes and structural characterization based on product ion spectra. Traditionally, metabolite detection is accomplished primarily on the basis of predicted molecular masses or fragmentation patterns of metabolites using triple-quadrupole and ion trap mass spectrometers. Recently, a novel mass defect filter (MDF) technique has been developed, which enables high-resolution mass spectrometers to be utilized for detecting both predicted and unexpected drug metabolites based on narrow, well-defined mass defect ranges for these metabolites. This is a new approach that is completely different from, but complementary to, traditional molecular mass- or MS/MS fragmentation-based LC/MS approaches. This article reviews the mass defect patterns of various classes of drug metabolites and the basic principles of the MDF approach. Examples are given on the applications of the MDF technique to the detection of stable and chemically reactive metabolites in vitro and in vivo. Advantages, limitations, and future applications are also discussed on MDF and its combinations with other data mining techniques for the detection and identification of drug metabolites. Copyright © 2009 John Wiley & Sons, Ltd. [source] An algorithm for thorough background subtraction from high-resolution LC/MS data: application to the detection of troglitazone metabolites in rat plasma, bile, and urineJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 9 2008Haiying Zhang Abstract Interferences from biological matrices remain a major challenge to the in vivo detection of drug metabolites. For the last few decades, predicted metabolite masses and fragmentation patterns have been employed to aid in the detection of drug metabolites in liquid chromatography/mass spectrometry (LC/MS) data. Here we report the application of an accurate mass-based background-subtraction approach for comprehensive detection of metabolites formed in vivo using troglitazone as an example. A novel algorithm was applied to check all ions in the spectra of control scans within a specified time window around an analyte scan for potential background subtraction from that analyte spectrum. In this way, chromatographic fluctuations between control and analyte samples were dealt with, and background and matrix-related signals could be effectively subtracted from the data of the analyte sample. Using this algorithm with a ± 1.0 min control scan time window, a ± 10 ppm mass error tolerance, and respective predose samples as controls, troglitazone metabolites were reliably identified in rat plasma and bile samples. Identified metabolites included those reported in the literature as well as some that had not previously been reported, including a novel sulfate conjugate in bile. In combination with mass defect filtering, this algorithm also allowed for identification of troglitazone metabolites in rat urine samples. With a generic data acquisition method and a simple algorithm that requires no presumptions of metabolite masses or fragmentation patterns, this high-resolution LC/MS-based background-subtraction approach provides an efficient alternative for comprehensive metabolite identification in complex biological matrices. Copyright © 2008 John Wiley & Sons, Ltd. [source] Automated software-guided identification of new buspirone metabolites using capillary LC coupled to ion trap and TOF mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2006Anabel S. Fandiño Abstract The identification and structure elucidation of drug metabolites is one of the main objectives in in vitro ADME studies. Typical modern methodologies involve incubation of the drug with subcellular fractions to simulate metabolism followed by LC-MS/MS or LC-MSn analysis and chemometric approaches for the extraction of the metabolites. The objective of this work was the software-guided identification and structure elucidation of major and minor buspirone metabolites using capillary LC as a separation technique and ion trap MSn as well as electrospray ionization orthogonal acceleration time-of-flight (ESI oaTOF) mass spectrometry as detection techniques. Buspirone mainly underwent hydroxylation, dihydroxylation and N -oxidation in S9 fractions in the presence of phase I co-factors and the corresponding glucuronides were detected in the presence of phase II co-factors. The use of automated ion trap MS/MS data-dependent acquisition combined with a chemometric tool allowed the detection of five small chromatographic peaks of unexpected metabolites that co-eluted with the larger chromatographic peaks of expected metabolites. Using automatic assignment of ion trap MS/MS fragments as well as accurate mass measurements from an ESI oaTOF mass spectrometer, possible structures were postulated for these metabolites that were previously not reported in the literature. Copyright © 2006 John Wiley & Sons, Ltd. [source] Rapid screening and characterization of drug metabolites using a new quadrupole,linear ion trap mass spectrometerJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2003Gérard Hopfgartner Abstract The application of a new hybrid RF/DC quadrupole,linear ion trap mass spectrometer to support drug metabolism and pharmacokinetic studies is described. The instrument is based on a quadrupole ion path and is capable of conventional tandem mass spectrometry (MS/MS) as well as several high-sensitivity ion trap MS scans using the final quadrupole as a linear ion trap. Several pharmaceutical compounds, including trocade, remikiren and tolcapone, were used to evaluate the capabilities of the system with positive and negative turbo ionspray, using either information-dependent data acquisition (IDA) or targeted analysis for the screening, identification and quantification of metabolites. Owing to the MS/MS in-space configuration, quadrupole-like CID spectra with ion trap sensitivity can be obtained without the classical low mass cutoff of 3D ion traps. The system also has MS3 capability which allows fragmentation cascades to be followed. The combination of constant neutral loss or precursor ion scan with the enhanced product ion scan was found to be very selective for identifying metabolites at the picogram level in very complex matrices. Owing to the very high cycle time and, depending on the mass range, up to eight different MS experiments could be performed simultaneously without compromising chromatographic performance. Targeted product ion analysis was found to be complementary to IDA, in particular for very low concentrations. Comparable sensitivity was found in enhanced product ion scan and selected reaction monitoring modes. The instrument is particularly suitable for both qualitative and quantitative analysis. Copyright © 2003 John Wiley & Sons, Ltd. [source] Analytical strategies for identifying drug metabolitesMASS SPECTROMETRY REVIEWS, Issue 3 2007Chandra Prakash Abstract With the dramatic increase in the number of new chemical entities (NCEs) arising from combinatorial chemistry and modern high-throughput bioassays, novel bioanalytical techniques are required for the rapid determination of the metabolic stability and metabolites of these NCEs. Knowledge of the metabolic site(s) of the NCEs in early drug discovery is essential for selecting compounds with favorable pharmacokinetic credentials and aiding medicinal chemists in modifying metabolic "soft spots". In development, elucidation of biotransformation pathways of a drug candidate by identifying its circulatory and excretory metabolites is vitally important to understand its physiological effects. Mass spectrometry (MS) and nuclear magnetic resonance (NMR) have played an invaluable role in the structural characterization and quantification of drug metabolites. Indeed, liquid chromatography (LC) coupled with atmospheric pressure ionization (API) MS has now become the most powerful tool for the rapid detection, structure elucidation, and quantification of drug-derived material within various biological fluids. Often, however, MS alone is insufficient to identify the exact position of oxidation, to differentiate isomers, or to provide the precise structure of unusual and/or unstable metabolites. In addition, an excess of endogenous material in biological samples often suppress the ionization of drug-related material complicating metabolite identification by MS. In these cases, multiple analytical and wet chemistry techniques, such as LC-NMR, enzymatic hydrolysis, chemical derivatization, and hydrogen/deuterium-exchange (H/D-exchange) combined with MS are used to characterize the novel and isomeric metabolites of drug candidates. This review describes sample preparation and introduction strategies to minimize ion suppression by biological matrices for metabolite identification studies, the application of various LC-tandem MS (LC-MS/MS) techniques for the rapid quantification and identification of drug metabolites, and future trends in this field. © 2007 Wiley Periodicals, Inc., Mass Spec Rev [source] Rapid detection and characterization of reactive drug metabolites in vitro using several isotope-labeled trapping agents and ultra-performance liquid chromatography/time-of-flight mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 6 2009Timo Rousu Reactive metabolites are believed to be one of the main reasons for unexpected drug-induced toxicity issues, by forming covalent adducts with cell proteins or DNA. Due to their high reactivity and short lifespan they are not directly detected by traditional analytical methods, but are most traditionally analyzed by liquid chromatography/tandem mass spectrometry (LC/MS/MS) after chemical trapping with nucleophilic agents such as glutathione. Here, a simple but very efficient assay was built up for screening reactive drug metabolites, utilizing stable isotope labeled glutathione, potassium cyanide and semicarbazide as trapping agents and highly sensitive ultra-performance liquid chromatography/time-of-flight mass spectrometry (UPLC/TOFMS) as an analytical tool. A group of twelve structurally different compounds was used as a test set, and a large number of trapped metabolites were detected for most of them, including many conjugates not reported previously. Glutathione-trapped metabolites were detected for nine of the twelve test compounds, whereas cyanide-trapped metabolites were found for eight and semicarbazide-trapped for three test compounds. The high mass accuracy of TOFMS provided unambiguous identification of change in molecular formula by formation of a reactive metabolite. In addition, use of a mass defect filter was found to be a usable tool when mining the trapped conjugates from the acquired data. The approach was shown to provide superior detection sensitivity in comparison to traditional methods based on neutral loss or precursor ion scanning with a triple quadrupole mass spectrometer, and clearly more efficient detection and characterization of reactive drug metabolites with a simpler test setup. Copyright © 2009 John Wiley & Sons, Ltd. [source] Ultra-performance liquid chromatography coupled to linear ion trap mass spectrometry for the identification of drug metabolites in biological samplesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2006G. J. Dear The coupling of ultra-performance liquid chromatography, operating at elevated pressures, to a linear ion trap mass spectrometer provides a high-performance system suitable for drug metabolite characterisation. This system demonstrates improved chromatographic efficiency and sensitivity and at the same time provides diagnostic MSn data often critical for metabolite structural assignment. The linear ion trap was capable of dealing with the high chromatographic efficiencies and hence narrow peak widths associated with 1.7,µm particle-packed column separations. Polarity switching and data-dependent MSn data were generated with ease, and applied to the identification of metabolites found in human plasma. Copyright © 2006 John Wiley & Sons, Ltd. [source] Loss of Ammine from Platinum(II) Complexes: Implications for Cisplatin Inactivation, Storage, and Resistance,CHEMISTRY - A EUROPEAN JOURNAL, Issue 9 2005Justin Kai-Chi Lau Abstract Potential consequences of the binding of the anticancer drug cisplatin to various biomolecules in the cell have been investigated by using a combined density functional theory and continuum dielectric model approach. Since the ammine ligands remain coordinated at the metal upon formation of the most frequent DNA adducts, whereas they were found to be displaced from the metal upon formation of drug metabolites, we have analyzed the factors governing ammine loss from platinum(II) complexes as a possible pathway of cisplatin inactivation. The calculations systematically show the effect of 1) the trans ligand, 2) the charge of complex, 3) the nucleophile, and 4) the environment on the thermodynamic instability and kinetic lability of the platinum,ammine bonds. After initial binding of cisplatin hydrolysis products to thioethers or thiols, loss of the ammine trans to this sulfur ligand rather than replacement of the sulfur ligand itself by other nucleophiles like guanine-N7 is predicted to be the predominant reaction. The results of this study contribute to an understanding of the modes of cisplatin inactivation prior to DNA binding, for example, by elevated glutathione levels in cisplatin-resistant cancer cells. [source] Treatment of erythema multiforme, Stevens,Johnson Syndrome, and toxic epidermal necrolysisDERMATOLOGIC THERAPY, Issue 4 2002Klemens Rappersberger The "erythema multiforme disease spectrum" comprises four distinct, severe, clinical subvariants: (1) bullous erythema multiforme (bullous-EM), (2) Stevens,Johnson syndrome (SJS), (3) SJS,toxic epidermal necrolysis (TEN)-overlap syndrome, and (4) TEN. These diseases are closely related to severe mucocutaneous intolerance reactions that are mostly elicited by drugs/drug metabolites and associated with a high mortality rate. Old age and area of detached skin negatively influence the course of disease, and early withdrawal of causative drugs with short half-life is a positive prognostic factor. Therapeutic management represents a multidisciplinary challenge for colleagues from various specialities including specialized nurses and usually can be performed at a dermatologic ward unless technical equipment of an intensive care unit is needed. Topical therapy with biologic and (semi-)synthetic dressings is aimed at early re-epithelialization and the prevention of scarring, synechia formation, and infection. Systemic treatment includes antibiotics, fluid and electrolyte replacement, protein preparations and blood products, etc. Various anti-inflammatory and immunosuppressive treatment regimens with corticosteroids, cyclosporine A, cyclophosphamide, plasmapheresis have been considered to halt ongoing immunologic pathomechanisms, and some of these have shown significant efficacy. However, because we lack formal clinical trials, none of these regimens can be definitively proposed as a therapy of choice in any of the severe clinical variants of the EM spectrum. [source] | |||||||||||||