Ethyl glucuronide

Alcohol consumption is very difficult to assess. There is widespread belief that individuals underreport their intake and there are no reliable laboratory tests available for definitive diagnosis of alcohol abuse. A combination of abnormalities in the plasma activity of gamma-glutamyl transferase (GGT or yGT), AST and reduction in erythrocyte mean cell volume (MCV) maybe useful and all are routine lab. tests. A potential marker of interest is carbohydrate-deficient transferrin (CDT) which is an abnormal isoform of serum transferrin arising due to defects in the attachment of carbohydrate chains to the protein core. Unfortunately, CDT is a somewhat specialized test, not performed by most laboratories. Other markers which have attracted some research interest are ethyl sulphate and ethyl glucuronide. Excretion in the urine of these metabolites occurs for up to 50 hours after binge drinking so they offer a useful index of recent heavy alcohol intake. 

Kfivankova, L., Caslavska, J., Malaskova, H., Gebauer, P., and Thormann, W. (2004). Analysis of ethyl glucuronide in human serum by capillary electrophoresis with sample self-stacking and indirect detection./. Chromatogr. A 1081, 2 — 8. 

Klys M, Sdslowski M, Rojek S et al (2005) A fatal clomipramine intoxication case of a chronic alcoholic patient application of postmortem hair analysis method of clomipramine and ethyl glucuronide using LC/APCI/MS. Leg Med (Tokyo) 7 319-325... 

Aderjan, R. E., Besserer, K., Sachs, H., Schmitt, G. G., and Skopp, G. A., Ethyl glucuronide — a nonvolatile ethanol metabolite in human hair, presented at TIAFT/SOFT Joint Congress, Tampa, October 31 to November 4,1994, paper 12. 

W. Weimmann, P. Schaefer, et al.. Confirmatory analysis of ethyl glucuronide in urine by liquid chromatography/electrospray-tandem mass spectrometry, J. Am. Soc. Mass Spectrom. 15, 188-193 (2004). 

Another therapeutic class to be briefly discussed is that of the lipid-lowering agents known as fibrates, e.g., clofibrate and fenofibrate (8.5). Here also, the acidic metabolite is the active form clofibrate (an ethyl ester) is rapidly hydrolyzed to clofibric acid by liver carboxylesterases and blood esterases [11], Human metabolic studies of fenofibrate (8.5), the isopropyl ester of fenofibric acid, showed incomplete absorption after oral administration, while hydrolysis of the absorbed fraction was quantitative [12], This was followed by other reactions of biotransformation, mainly glucuronidation of the carboxylic acid group. 

UGTIAI has an important role in the metabolism of irinotecan, etoposide, epiru-bicine, and tipifamib. Irinotecan is a camptothecin derivative used in the treatment of metastatic colon cancer. Irinotecan is a prodrug since it is activated to Ethyl-10-hydroxycamptothecin (SN-38) by carboxyl esterase to exert its antitumor activity mediated by the inhibition of topoisomerase I. SN-38 undergoes UGTIAI-catalyzed glucuronide conjugation to form the inactive SN-38 glucuronide (SN-38G). 

A full characterization of the metabolic pathways of CPT-11 in human cancer patients has not been undertaken. The incomplete recovery of the irinotecan dose based on urine and bile determinations of irinotecan, SN-38, and SN-38 glucuronide suggests the presence of additional unidentified metabolites. Recently, a major metabolite, 7-ethyl-10-[4-A-(5-aminopenatoic acid)-l-piperidino]carbonyloxycamptothecin, has been identified in dogs and humans, suggesting the presence of an additional metabolic pathway (18). Renal clearance has not been reported to be a major route of elimination for these compounds in humans. 

A half-life of 6 min for metabolism of di(2-ethylhexyl) adipate has been determined in rat small intestinal mucous membrane homogenates. The dominant urinary metabolite of di(2-ethylhexyl) adipate (500 mg/kg bw) in male Wistar rats is adipic acid, which accoimts for 20-30% of the administered oral dose. The other major metabolite which was found only in the stomach is mono(2-ethylhexyl) adipate (Takahashi et al., 1981). In cynomolgus monkeys, the glucuronide of mono(2-ethyl-hexyl) adipate and traces of unchanged di(2-ethylhexyl) adipate were foimd in the urine (BUA, 1996). 

Ciotti M, Basu N, Brangi M et al. Glucuronidation of 7-ethyl-10-hydroxycamptothecin (SN-38) by the human UDP-glucuronosyltransferases encoded at the UGTl locus. Biochem Biophys Res Commun 1999 260 199-202. 

Villeneuve L, Girard H, Fortier LC et al. Novel functional polymorphisms in the UGT1A7 and UGT1A9 glucuronidating enzymes in Caucasian and African-American subjects and their impact on the metabolism of 7-ethyl-10-hydroxycamptothecin and flavopiridol anticancer drugs. J Pharmacol Exp Ther 2003 307 117-128. 

Girard H, Villeneuve L, Court MH et al. The novel UGT1A9 intronic 1399 polymorphism appears as a predictor of 7-ethyl-10-hydroxycamptothecin glucuronidation levels in the liver. DrugMetab Dispos 2006 34 1220-1228. 

In swine orally dosed with thiophanate, the major metabolic product in the urine was 2-aminobenzimidazole, the parent drug being present only in trace amounts. Lower levels of the 2-aminobenzimidazole glucuronide conjugate and the lobendazole metabolite were also detected. Trace amounts of thiophanate were also present in the feces, which further contained lobendazole and its 5-hydroxylated metabolite. Kidney and liver tissues were found to contain 4 metabolites, two of which were identified as the l,2,-(phenylene-bisiminocarbonothioyl)-biscarbamic acid 0-ethyl-0-(l-hydroxyethyl)ester and the (phenylene-(bisimino-carbonothioyl)) biscarbamic acid O-ethyl-O-vinyl ester. 

An indirect enzyme immunoassay suitable for the determination of chloramphenicol and its glucuronide was developed for the analysis of urine, milk, tissue, and eggs as well (48). In this assay, chloramphenicol succinate was coupled to both bovine serum albumin and horseradish peroxidase by a mixed anhydride procedure. Unlike tissue and egg samples, urine and defatted milk could be directly analyzed, but when an ethyl acetate extraction was employed in milk analysis, the limit of detection was lowered at least 10 times. 

The cinchonidine salt (1.58 g.) of the glucuronide was suspended in 64 ml. of water and 40 ml. of ethyl acetate (analytical grade), and 2.4 ml. of concentrated hydrochloric acid (or 11 N sulfuric acid) was stirred in until dissolution was complete. After quantitative transfer to a separating funnel and shaking, the aqueous layer was reextracted four times (with 20 ml. of ethyl acetate each time). The combined ethyl acetate solutions were filtered, evaporated rapidly under diminished pressure, and dried thoroughly under diminished pressure. The residue was redissolved in 70 ml. 

---