METABOLISM OF IMIPROTHRIN ISOMERS IN RATS - BIOTRANSFORMATION AND EXCRETION

The biotransformation and excretion of imiprothrin ([2,5-dioxo-3-(2-pr opynpl)-1-imidazolidinyl]methyl (1R)-cis, trans-chrysanthemate), a nov el pyrethroid, was examined by dosing (1R)-trans- or (1R)-cis-[imidazo lidinyl-5-C-14]imiprothrin orally to male and female rats at 1 (low do se) and 200 mg/kg (high dose). Elimination of the trans- and cis-isome rs was rapid, and almost all of the dosed (14) was excreted into urine , feces and expired air within 7 days, with the former route predomina ting (more than 83% of the dosed C-14). C-14-Tissue residues on the 7t h day after administration were generally low in ail dosed groups. The re were no marked sex-related differences in the rate of C-14-excretio n and the C-14-tissue residues within either treatment group. To eluci date metabolic pathways of imiprothrin, major urinary metabolites were isolated using (1R)-cis-[imidazolidinyl-5-C-14]imiprothrin and chroma tographic techniques, with identification by spectroanalyses (NMR and MS). Metabolites in urine or feces were also identified and quantified by HPLC analyses using these isolated metabolites as standards. No ma rked sex-related differences in the metabolite profiles were observed within dose groups. Based on the identified metabolites, the main meta bolic reactions of imiprothrin in rats are 1) cleavage of the ester li nkage, 2) cleavage of the imido-methylene linkage, 3) hydroxylation of the imidazolidine ring, 4) dealkylation of the 2-propynyl group and 5 ) oxidation at tile omega-trans-methyl group in the isobutenyl side ch ain.