Plasma metabolites profiling

FIGURE 10.9 Representative plasma metabolite profiles of a radiolabeled drug candidate in rats (a), dogs (b), and humans (c). The pooled plasma samples from radiolabeled ADME studies after an oral administration were collected around the maximum concentration of the drug. The radioactivity profiles were determined by offline HPLC-TopCount (four functions per min and 10 min counting time). Approximately, 400 9000 DPM of radioactivity was injected. 

Most of the tests that were developed for detection of cannabinoids in plants have shown that antibodies are specific for the cannabinoid structure. Because of this specifity these tests can be extensively applied for the detection of cannabinoids and metabolites in human body fluids such as plasma, urine, and oral fluids. Many different kits based on these methods were developed and they are commercially available, for example Oratect, Branan or Uplink, and OraSure. We must consider, however, that no humans have the same metabolite profile in their blood and that cross-reactivity may always occur [122,123]. Nevertheless, these tests offer a simple way of excluding most of the suspicious samples, but the results still have to be confirmed with a second method such as GC-MS [124,125]. 

Our laboratory used the QTRAP MS/MS system for both quantitative analysis and metabolite profiling when assaying plasma samples. We found it useful to use three rules for deciding when to report a possible metabolite ... 

The study should provide unique information on the plasma-concentration profiles of parent drug and metabolite. The rates and extended excretion in urine, faeces and, if appropriate, expired air can be defined. 

Figure 6.6. Metabolite profiles of omeprazole in human plasma (a) base peak ion chromatogram of unprocessed data and (b) base peak ion chromatogram of MDF-processed data exhibiting all metabolite peaks present and some endogenous peaks. High-resolution LC-MS data were obtained for a human plasma sample spiked with omeprazole metabolites generated by microsomal incubation (the equivalent of a 1.0-mL plasma injection). A MDF ivas set at 50 mDa around the apparent mass defect of the omeprazole ion.

Although the advantages associated with online plasma extraction are attractive, care must be taken to monitor the recovery of dmg-related material during the extraction process. Unlike quantitative plasma analysis, where poor recovery only affects the limit of quantitation, the recovery of all drug-related components in metabolite profiling studies must be high in order to ensure that the quantitative data are meaningful. 

Jensen et al. [125] investigated an HPLC/ICP-MS (inductively coupled plasma mass spectrometry) with sulfur-specific detection, as a method for obtaining metabolite profiles for omeprazole administered as a 1 1... 

Fig. 4.8 HPLC radiometric metabolite profiling of extracts of (a) plasma,...

Rochat B et al (2008) Imatinib metabolite profiling in parallel to imatinib quantification in plasma of treated patients using liquid chromatography-mass spectrometry. J Mass Spectrom... 

Dahmane E et al (2010) An ultra performance liquid chromatography-tandem MS assay for tamoxifen metabolites profiling in plasma first evidence of 4 -hydroxylated metabolites in breast cancer patients. J Chromatogr B Analyt Technol Biomed Life Sci 878 3402-3414... 

Metabonomics (the quantitative measurement of time-related responses to stimuli within the body)17,18 may prove to be of some use to assess the potential of a material to elicit an irritant response following topical application. The concept being that certain stimuli change the metabolite profile in intermediate biochemical pathways. Analysis of body fluids such as urine, saliva, plasma, biopsy material, etc. produces a fingerprint of biochemical changes characteristic of the nature or site of a toxic (or other) effect. 

Conclusion A population PK model for the new compound NS2330 and its major metabolite could successfully be developed describing the plasma concentrationtime profiles of the parent compound and its metabolite in Alzheimer s disease patients. 

Samples are analyzed by a suitable chromatographic system, typically HPLC with on-line radiodetection. Metabolite profiles in plasma and tissues are given as percent of radioactivity present in total. Profiles in urine, bile and feces are given as percent of the dose administered. 

The total radioactivity minus the parent compound concentration (determined by the bioanalytical method) in a specimen estimates the amount of metabolites present. If the difference is minimal and does not change over time, the extent of metabolism is low. For plasma or serum specimens, a small difference indicates that metabolites are not present in systemic circulation. For bile or urine specimens, high levels of radioactivity suggest a primary route of elimination for the parent and metabolites. For a drug candidate cleared primarily by metabolism, a preliminary metabolite profile in urine and bile can determine the number of potential metabolites. When the level of a metabolite in a matrix is high, attempts to isolate and identify the metabolite can be undertaken. If sufficient quantities are obtained, the metabolite s pharmacologic and toxicologic... 

An interesting feature that arises from comparison of this KC data with previous fed/fasted Hf data [79] is that administration of Hf with a fatty meal produces a similar plasma Hfm/Hf plasma AUC profile to that obtained after coadministration of Hf with KC in the fasted state (and very different to the Hfm/ Hf ratio after normal fasted administration). In both the fed/fasted and the KC studies the Hf/Hfm ratio was similar (0.47 and 0.54, respectively) after fasted administration (no food/ketaconazole, respectively). In contrast, in both the fed state and after co-administration with KC, the Hfm/Hf metabolite ratio was significantly reduced (0.08 and <0.05, respectively). Similar alterations in the magnitude of the Hfm/Hf ratio after feeding have also been demonstrated in humans... 

These preclinical drug metabolism studies may also include metabolite profiling in plasma, selected tissues, urine, and bile to assess the distribution and disposition of potentially important metabolites, such as those having a level 5% or greater relative to the parent compound. Metabolite profiling requires a technique to separate the parent compound from metabolites and other endogenous compounds. For small organic molecules, HPLC is usually the method of choice. For macromolecules, gel or capillary electrophoresis techniques can be defined with sufficient resolution capability to separate the... 

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