Metabolism of Empenthrin Isomers in Rats

Abstract

On single oral administration of (lR)-cis- or (1R)-trans-empenthrin [(1?S)-l-ethynyl-2-methyl-2-pentenyl (1R)-cis-trans-chrysanthemate], labeled with 14C at C-l carbon of the alcohol moiety, at 3 and 150 mg/kg or 3 and 600 mg/kg, respectively, rats excreted 14C rapidly and substantially completely into the urine and feces within 7 days after administration. 14C remaining in the body was less than 0.4% of the dose on the 7th day. Urinary, fecal and exhaled 14C excretion accounted for 22-41%, 60-74% and 1-2% of the dose, respectively. 14C concentrations in the tissues reached maxima at 1 to 8 hr after dosing the cis- or trans-isomer at 3 mg/kg and decreased thereafter. The concentrations were higher in the liver and kidney than other tissues. The fat retained 14C longer than other tissues in rats treated with the cis-isomer. Notable sex-related difference was not observed in distribution or excretion of radioactivity. 14C tissue residues were lower in rats receiving the trans-isomer than in those receiving the cis-isomer. The parent compound accounted for 7-13% and 17-26% of the dose in the feces of rats receiving the cis- and trans-isomer, respectively. Main biotransformations were cleavage of the ester linkage and glucuronidation of the formed alcohol. Oxidation of a methyl group in the acid moiety and a methylene group in the alcohol moiety, and hydration of the triple bond in the alcohol moiety were also observed. © 1992, Pesticide Science Society of Japan. All rights reserved.