Metabolism of (Z)‑(1R,3R)‑Profluthrin in Rats

When [benzyl-α-14C]-labeled (Z)-(1R,3R)-profluthrin (2,3,5,6-tetrafluoro-4-methylbenzyl (Z)-(1R,3R)-2,2-dimethyl-3-(prop-1-enyl) cyclopropanecarboxylate, a newly developed pyrethroid) was administered orally to rats at 1 mg/kg, around 70% was absorbed, metabolized, and mainly excreted into urine within 48 h. Radioactivity in plasma reached Cmax at 6–8 h, and decreased (half-life; 37–52 h). A similar tendency was observed also in tissues. Absorption rate was slightly lower at high dose, while kinetics and distribution did not change. Eight metabolites were detected in urine and one in feces. Most of the 14C in feces was unabsorbed (Z)-(1R,3R)-profluthrin. The main metabolic reactions were ester cleavage, hydroxylation of the methyl group on the C4-position of the benzene ring, and its glucuronidation or oxidation to carboxylic acid. Oxidation of the geminal dimethyl on the cyclopropane-C2 to carboxylic acid, oxidation followed by hydration of the propenyl double bond, and ω-oxidation to carboxylic acid and mercapturic acid conjugation of the benzyl alcohol were observed as minor reactions.