The Fate of the Herbicide Flamprop-isopropyl (Barnon*) in Rats and Dogs

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Abstract
1. [14C]Flamprop-isopropyl (Barnon) administered orally to rats and dogs is excreted mostly via the faeces (90·5% and 76·3% in male and female rats respectively and 53% in dogs). Elimination was rapid from both species, and > 96% of the dose of 14C was excreted by rats 0–48 h after dosing. Distribution of 14C between urine and faeces was different in male and female rats, but the same for dogs of either sex. 2. The predominant metabolic pathway in both species was loss of the iso-propyl group; the resulting carboxylic acid was excreted free and as the ester glucuronide. 3. Aromatic hydroxylation occurred at the para- and meta-positions of the N-benzoyl ring; the presence of a 3,4-dihydroxybenzoyl metabolite (but no dihydrodiol) suggests that arene oxide formation is involved. However, direct hydroxylation at position 3 cannot be precluded. Aromatic hydroxylation occurred with the following facility (0–48 h): male rat, 18%; female rat, 13%; dog (either sex), 2%. 4. Hydroxylation occurred readily in the isopropyl side chain yielding mostly a propan 1,2-diol ester in the dog. In the rat, this metabolite was mostly oxidized to yield a 2-lactyl ester.