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1. The urinary metabolites of the anti-convulsant compound 4-amino-1-(2,6-difluorobenzyl)-1H-1,2,3-triazolo[4,5-c]-pyridine hydrochloride (GI265080) obtained following a single oral dose to man have been detected and quantified relative to each other using [sup 19]F-NMR spectroscopy. 2. The human urinary metabolites of GI265080 were isolated using semipreparative HPLC and unequivocally characterized using [sup 1]H-NMR spectroscopy, two-dimensional heteronuclear NMR spectroscopy and mass spectrometry. The assignments of the N-(5)oxide and the N-(5)-O-glucuronide metabolites of GI265080 were further confirmed by independent synthesis. The urinary metabolites obtained following single oral doses to dog and rat have also been isolated and characterized. 3. The human urinary metabolites of GI265080 comprise the N-(5)-oxide, the quaternary N[sup +]-(5)-glucuronide, the 7-hydroxy glucuronide and a glucuronide conjugate of the N-(5)-oxide. The N-(5)-O-glucuronide conjugate is a novel species in human metabolism and is a significant route of elimination of GI265080 in man. 4. The urinary metabolites of the potential anti-convulsant GW273293 (6-amino-3-(2,3,5-trichlorophenyl)pyrazin-2-ylamine) obtained following a single oral dose to man have also been isolated and characterized. The formation of a novel N-O-glucuronide was also observed and was shown to constitute a significant route of elimination of GW273293 in man. [ABSTRACT FROM AUTHOR]

Mr. Dear's article is based upon a study he made whilst attending the Senior Command Course at the Police College, Bramshill. It constitutes a general appreciation of the position regarding coloured immigrant communities with particular reference to problems presented to the police. [ABSTRACT FROM PUBLISHER]

Definitive information on the metabolism of a drug candidate in humans is achieved through dosing radiolabelled drug as part of a clinical study, and is typically conducted post-proof of concept in Phase III of the clinical development plan. Here we describe a novel approach, using preparative high performance liquid chromatography and cryoprobe-nuclear magnetic resonance spectroscopy, to determine the human systemic exposure to a drug and its metabolites using samples derived from Phase I clinical studies. Using the described methodology, novel human plasma metabolites, as low as 10 ng/ml can be detected and quantified. This provides an opportunity, early in the development process to understand the potential role of metabolites in the safety and efficacy of drugs in humans.

The recent commercial availability of small particle packed columns (<2 microm) and associated instrumentation capable of withstanding the high pressures of such columns, has lead to an increase in the application of so called ultra-performance liquid chromatography. The improved efficiency, resolution and peak capacity of these columns, when coupled to mass spectrometry, provides particular benefit for the identification of drug metabolites in complex biological samples. In this work, the ability of ViewLux, a microplate imager, to act as a suitable radiodetection system for ultra-performance liquid chromatography methods is assessed. The system demonstrates robustness and sensitivity comparable to a microplate scintillation counter (TopCount) more typically used for off-line metabolite radiodetection. The ViewLux is also used here to undertake successful metabolite profiling of actual samples, for two investigational drug candidates, using both 96- and 384-well yttrium silicate microplates.

The recent commercial availability of small particle packed columns (<2microm) and associated instrumentation capable of withstanding the high pressures of such columns, has lead to an increase in the application of so called ultra-performance liquid chromatography (UPLC). It has recently been shown that the improved efficiency, resolution and peak capacity of these columns, when coupled to mass spectrometry, provides particular benefit for the identification of drug metabolites in complex biological samples. In this work, the ability of TopCount, a microplate scintillation counter, to act as a suitable radiodetection system for ultra-performance liquid chromatography methods is tested. TopCount, has innumerable benefits over more traditional on-line radioactivity flow detection methods, when dealing with the narrow peak widths and small peak volumes associated with the enhanced efficiency of sub-2microm columns. The system is tested for robustness and sensitivity, and then used to undertake successful metabolite profiling of actual samples, and the data compared to traditional HPLC with on-line radioactivity flow detector.

The in-vitro metabolism of GW420867X ((S)-2-ethyl-7-fluoro-3-oxo-3, 4-dihydro-2H-quinoxaline-1-carboxylic acid isopropyl ester), a quinoxaline drug for the potential treatment of HIV, has been studied with singly expressed human cytochromes P450 (CYP 450). No biotransformation of [14C]GW420867X was evident in the presence of any of the CYP 450 isoforms, with the exception of CYP 450 1A2, where a single metabolite was observed in the HPLC radiochromatograms of enzyme incubations with the test compound. The structure of this metabolite was determined by nuclear magnetic resonance spectroscopy and mass spectrometry, and was shown to correspond to the replacement of the aromatic fluorine of GW420867X with a hydroxyl group. Thus, it appeared that CYP 450 1A2 catalysed the specific defluorination of GW420867X, presumably during formation of an arene oxide intermediate during aromatic hydroxylation.

The methodology described demonstrates, for the first time, the feasibility of performing pharmacokinetic studies in the serially bled mouse model to support the early development of discovery compounds. Sample analysis, using capillary high performance liquid chromatography combined with tandem mass spectrometry, has facilitated the achievement of this milestone and has successfully been applied to determine pharmacokinetic information following both intravenous and oral administration of a single discovery compound. The methodologies described demonstrate potential for a reduction in the amount of new chemical entity required to undertake pharmacokinetic studies. Typically, such studies are performed in larger rodents with a significantly increased body mass (ten times in the case of the rat) and therefore it follows that to undertake the same experiment in the mouse would require ten times less compound to effect an equivalent dose. Conventionally, pharmacokinetic studies to obtain both intravenous and oral information, e.g. clearance and half-life, and the resultant bioavailability have been performed using two parallel groups of rodents, collecting blood by exsanguination, separating off the plasma and analysing this using conventional liquid chromatography/tandem mass spectrometry. The use of capillary high performance liquid chromatography (HPLC) has facilitated the analysis of small volume blood samples by increasing the effective sensitivity of the analytical method. Consequently, we have established a protocol for serially bleeding mice thus reducing the number of animals and so further reducing the amount of compound required for such experiments. This paper reports data obtained from collected and processed blood volumes of <20 microL with the subsequent injection of only 1 microL of precipitated extract onto a capillary column., (Copyright 1999 John Wiley & Sons, Ltd.)

Cisatracurium, (1R, 1'R, 2R, 2'R)-2,2-[1,5-pentanediylbis-[oxy(3-oxo- 3,1-propanediyl]]bis[1-[(3,4-dimethoxyphenyl)-methyl]-1,2,3,4- tetrahydro-6,7-dimethoxy-2-methylisoquinolinium] dibenzenesulphonate (51W89), is an intermediate-acting neuromuscular blocking agent. 51W89 is one of ten isomers contained in Tracrium (atracurium besylate) and represents approximately 15 percent of the atracurium mixture. Clinical studies have indicated that 51W89 is more potent and is significantly weaker as a histamine releaser than atracurium. In vitro studies in human plasma have shown that, like atracurium, 51W89 spontaneously degrades at physiological pH by Hoffmann elimination to form laudanosine and the quaternary monoacrylate. Subsequent ester hydrolysis of the monoacrylate generates the monoquaternary alcohol. In rat plasma, 51W89 is also metabolized by non-specific carboxylesterases to the monoquaternary alcohol and the monoquaternary acid, the former being rapidly hydrolysed further to the more stable acid. It has been reported that laudanosine can be further metabolized via N-dimethylation to yield tetrahydropapaverine. The rate-limiting step in the degradation of 51W89 in human plasma is Hofmann elimination, whilst in rat plasma, the action of non-specific carboxylesterases is rate limiting. As part of the development of 51W89, the disposition of 14C-51W89 following a single intravenous bolus dose was studied in various animal species and humans. In the present work, we describe the identification of 51W89 metabolites in urine and bile from these studies by high performance liquid chromatography/mass spectrometry using pneumatically-assisted electrospray ionization coupled to an on-line radioactivity monitor.(ABSTRACT TRUNCATED AT 250 WORDS)

Six microcystins were identified in a laboratory culture of the cyanobacterium (blue-green alga) Microcystis aeruginosa PCC 7813 using high-performance liquid chromatography coupled with diode array detection (HPLC-DAD) and mass spectrometry (LC-MS). The toxins were purified and further characterized by amino acid analysis and tandem mass spectrometry (MS-MS). The presence of the previously reported microcystin-LR and microcystin-LY was confirmed. Two further microcystins were characterized as microcystin-LW and microcystin-LF. Another two toxins were partially characterized and are believed to be an analog of microcystin-LR (molecular weight 1008) and microcystin-LM (molecular weight 969). Natural bloom material of M. aeruginosa collected from 2 reservoirs was found to have similar microcystin profiles using HPLC-DAD and LC-MS, indicating the widespread occurrence of these microcystin variants. In addition, the presence of 5 of the microcystins was confirmed in the rumen contents of a lamb by LC-MS and LC-MS-MS, providing the first report of microcystins identified in an animal suspected of being poisoned by cyanobacterial hepatotoxins.