Metabolite assay

While covalent binding studies have an advantage over the reactive metabolite assay in that they provide a quantitative estimate of covalently bound drug to proteins and therefore an indirect measure of reactive metabolite formation, there are no studies to date which show a correlation between the extent of covalent binding and/or reactive metabolite formed and the probability that a drug is... 

Gibson KM, Baumann C, Ogier H, Rossier E, Vollmer B, Jakobs C (1994) Pre- and postnatal diagnosis of succinic semialdehyde dehydrogenase deficiency using enzyme and metabolite assays. J Inherit Metab Dis 17 732-737... 

Commonly used methods for caffeine and metabolite ) assay in plasma or urine involve an extraction step followed by HPLC with UV detection (Krul and Hageman 1998a Rasmussen and Bosen 1996 Schreiber-Deturmeny and Bruguerolle 1996). Urine needs to be acidified (pH 3.0-3.5) before sample freezing. 

Screening family members to identify asymptomatic individuals who have inherited AIP, VP, or HCP, and are therefore at risk for acute attacks, is an essential part of management of families with these disorders. Screening may be carried out by metabolite measurement, enzyme assay, DNA analysis, or a combination of these approaches. The most sensitive metabolite assays for the presymptomatic diagnosis of each disorder are listed in Table 32-7. These tests are almost always normal before puberty and therefore are not suitable for the investigation of children. In addition, urinary PEG excretion in AIP and the plasma fluorescence scan in VP may often be normal in asymptomatic adults shown by DNA analysis to be affected (Table 32-7). Measurement of the activity of the defective enzyme is more sensitive, but both sensitivity and specificity are limited by the overlap between activities in disease and in the normal population. Erythrocyte HMBS assay is widely used for the presymptomatic diagnosis of AIP. ... 

Baughman, T.M. Wells-Knecht, M. Wells-Knecht, K. Zhao, Z. Method Validation for a Glutathione-trapping Reactive Metabolite Assay Using Drugs with Structural Moieties Known to Produce Reactive Species, Drug Metab. Rev. 35(S2), 112 (2003). 

Carbofuran Metabolite Assay. Rapid detection of enhanced degradation of carbofuran in soil can be accomplished in two different manners. The first approach is to measure the actual amount of carbofuran remaining after application and compare this value with what might be expected to remain after a selected time. This concept has been used by FMC in the form of a test ticket that colorimetrically determines the amount of carbofuran based on inhibition of acetylcholinesterase. The diagnostic kit is manufactured by Enzy-Tek of Lenexa, KS (20). A disadvantage of this method is lack of specificity due to the ability of the test reagents to react with other soil insecticides and their metabolites that are also acetylcholinesterase inhibitors. 

Isofenphos Metabolite Assay. Racke and Coats (22) discovered a new metabolite of isofenphos, isopropyl salicylate, in cultures of isofenphos-degrading microorganisms isolated from enhanced soil. Since isopropyl salicylate is closely related to aspirin, we investigated methods currently used in the medical diagnostics field. The method of Sunshine (23.) is used by coroners for... 

There are numerous ways to exploit the calorimetric detection principle in combination with biological materials, not only in metabolite assays, but also for analyses of proteins and other macromolecules as well as for whole cells. These include metabolite determination, bioprocess monitoring, measurements of enzymic activities in separation procedures, determinations in organic solvents, and miniaturized thermal biosensors. 

The three metabolites assayed produced the same effect on the insect used that the control (a commercial extract of the neem tree, containing 2% of azadirachtin), although at higher concentrations. 20a-hydroxy-tingenone was the most active compound among the three assayed. Pristimerin shows also a high antifeedant activity together with molt effect suppression. 

Fraser, A.D. Urinary screening for alprazolam, triazolam, and their metabolites with the EMIT d.a.u. benzodiazepine metabolite assay. J.Anal.ToxicoL, 1987, 11, 263—266... 

Potentiometric methods are less useful in metabolite assays because of the instability of the signals and the need of calibration. A special form of a potentiometric enzyme electrode, the enzymatically coupled field effect transistor is reviewed by Caras and Janata [31]. 

Naline E, Sanceaume M, Pays M, Advenier C.. / hcation of theophylline metabolite assays to the exploration of liver microsome oxidative function in man. Fundam Clin Pharmacol (1988)2,341-51. 

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