Carbamate metabolism

The carbamates, like the organophosphorus insecticides, are cholinesterase inhibitors. However, the reaction is rapidly reversible. Carbaryl has a half life in the soil of about 8 days and is decomposed by ultraviolet light. The carbamates metabolize rapidly in animals and show little, if any, propensity for storage in animal tissues. Additional properties and reactions of carbamates are discussed in the section on fungicides. 

Organophosphates and carbamates containing a pyrazole ring, useful as insecticides as discussed earlier (Section 4.04.4.1.2), are metabolized mainly through hydrolysis of the ester function (B-80MI40406). 

Resistance mechanisms associated with changes in toxicokinetics are predominately cases of enhanced metabolic detoxication. With readily biodegradable insecticides such as pyrethroids and carbamates, enhanced detoxication by P450-based monooxygenase is a common resistance mechanism (see Table 4.3). 

The repeated use of carbofuran and other carbamates has been associated with changes in the metabolic capacity of soil microorganisms (Suett 1986). Carbofuran... 

The carbamate insecticide aldicarb (Figure 2.13) that exerts its effect by inactivating acetylcholinesterase is metabolized by a flavin monooxygenase from rainbow trout to the sulfoxide, which is a more effective inhibitor (Schlenk and Buhler 1991). 

In addition to the parent fenoxycarb, residue methods for the two major metabolic products Ro-16-8797 CGA-294850, ethyl lV-2-[4-(4-hydroxyphenoxy) phenoxyethyljcarbamate, MW= 317.3 and Ro-17-3192 CGA-294851, (2-hydroxyethyl)-A-2-[4-(4-hydroxyphenoxy)phenoxyethyl]carbamate, MW = 333.3 in animal by-products were also developed. 

V-Ethyl carbamate esters of fenoldopam, used for treatment of acute circulatory failure, provide another example of a carbamate ester prodrug. The intrinsically short half-life and extensive first-pass metabolism of fenoldopam limit its oral administration. /V-Ethyl carbamate esters of fenoldopam provide elevated plasma fenoldopam levels and increases in the renal blood flow of significantly greater duration than when the parent compound is administered orally [30],... 

T Anders, LA Svensson. Bambuterol, a carbamate ester prodrug of terbutaline, as inhibitor of cholinesterases in human blood. Drug Metabol Dispos 16(5) 759-763,... 

A study has been carried out on the determination of triazine and carbamate pesticides and metabolities in seawater by HPLC with photodiode-array detection [393]. 

Modified from Zakour, H.R. 1980. Toxicity, Uptake and Metabolism of the /V-methyl-carbamate Pesticide Carbofuran by the Freshwater Bivalve Mollusc Glebula rotundata (Lamarck). Ph.D. Thesis, Rice University, Houston. 148 pp. 

Miller JA, Miller EC. The metabolic activation and nucleic acid adducts of naturally-occurring carcinogens recent results with ethyl carbamate and the spice flavors safrole and estragole. Br J Cancer 1983 48(1) 1-15. 

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