Metabolism of furametpyr. 2. 14C excretion, 14C concentrations in tissues, and amounts of metabolites in rats
2000
Nagahori, H. | Yoshino, H. | Tomigahara, Y. | Isobe, N. | Kaneko, H. | Nakatsuka, I.
14C-Labeled furametpyr [N-(1,3-dihydro-1,1,3-trimethylisobenzofuran-4-yl)- 5-chloro-1,3-dimethylpyrazole-4-carboxamide, Limber] was dosed to male and female rats at 1 (low dose) and 200 or 300 mg/kg (high dose). Elimination of furametpyr was rapid, and the dosed 14C was substantially excreted within 7 days (45.5-53.3% in feces, 44.1-53.8% in urine, and 0.01% in expired air). However, 14C excretion rate showed sex- and dose-related differences, more rapid in males at low dose. 14C concentrations in tissues decreased rapidly to generally low levels at 7 days (<0.004 ppm with the low dose and <1.1 ppm with the high dose). Forty metabolites were detected, and 13 metabolites and 4 glucuronides were identified. A small amount of unchanged furametpyr was detected in feces (0.1-0.5% of the dose). The major metabolites in tissues were N-demethylated metabolites. In a bile study, 52.5-54.2% of the dosed 14C was rapidly excreted into bile within 2 days. The absorption ratio was estimated to be >93.7% for the low dose (1 mg/kg). Major metabolites in bile were glucuronic acid conjugates of furametpyr hydroxides. On the basis of the results, furametpyr is substantially absorbed from the gastrointestinal tract after oral administration, rapidly distributed to tissues, extensively metabolized, and excreted into urine and bile or feces.
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