Pesticide residues in food — 2006: Toxicological ... - ipcs inchem

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ranged from 6 to 10 h. The tissues and carcass accounted for 1–7%, contents of the gastrointestinal tract
for < 3% and final cage wash for < 1% of the administered dose. There were no sex differences in the
distribution of radiolabel. Repeated administration of quinoxyfen did not affect the distribution of the
radiolabelled dose.
Comparison of the relative concentrations in bile and urine of intact and bile-duct cannulated rats
(Tables 2 & 3) indicated that enterohepatic recirculation is extensive with quinoxyfen at a dose of 10 mg/kg
bw. In bileduct cannulated rats, there was a marked difference in the amount of radiolabel in the faeces of
rats at 10 mg/kg bw (14.3%) compared with those at 500 mg/kg bw (57.3%) and in the amount of radiolabel
in the bile of rats at 10 mg/kg bw (54.4%) compared with those at 500 mg/kg bw (21.4%). These
findings indicated that absorption of quinoxyfen at a dose of 500 mg/kg bw dose was saturated.
Table 3. Distribution of radiolabel in bile-duct cannulated male rats
24 h after dosing with 14 C-quinoline-labelled quinoxyfen
Sample
Radioactivity (% of administered dose)
10 mg/kg bw 500 mg/kg bw
Urine 10.5 2.73
Faeces 14.33 57.30
Final cage wash 1.31 0.60
Carcass 5.16 2.16
Contents of the g astrointestinal tract 1.80 9.73
Skin 0.38 0.18
Bile 54.35 21.44
Total 87.85 94.14
From Schumann et al. (1995)
The distribution of radiolabel in organs and tissues (percentage of administered dose/g tissue)
48 h after treatment with a single dose of quinoline ring-labelled quinoxyfen at 10 mg/kg bw showed
that the highest amounts of radiolabel were present in perirenal fat (0.12 in males and 0.35 females)
> ovaries (0.07) > liver (0.027 in males and 0.045 in females) and kidneys (0.014 in males and 0.033
in females). Significant levels were found in the skin (Table 3). Similar amounts were obtained after
repeated dosing and a similar pattern after the higher dose of 500 mg/kg bw. There were no data on
tissue levels at times approximating to the plasma C max
(Schumann et al., 1995)
Goats
The metabolism, distribution, and elimination of 14 C-quinoxyfen, labelled either in the phenoxy
ring or the quinoline ring, was investigated in lactating dairy goats (n = 5; 51–60 kg bw). Two goats
were orally dosed with phenoxy 14 C-quinoxyfen (purity, > 98%), twice per day for five consecutive
days, at a concentration of 10.7 mg/kg feed. Similarly, two goats were treated with quinoline
14
C-quinoxyfen, twice per day for five consecutive days, at a concentration of 11.7 mg/kg feed. The
remaining goat was used as the untreated control animal. Urine and faeces were collected at intervals
of 24 h until sacrifice. Milk samples were collected before the first treatment with quinoxyfen, and
then twice daily throughout the study period until animals were sacrificed. The weights of urine,
faeces, cage wash and milk samples were recorded, and total radioactivity was measured using LSC.
Faecal samples were homogenized with water and subjected to combustion analysis before analysis
by LSC. Goats were sacrificed 16 h after the final dose, and samples of the following fluids/tissues
were collected for total radiolabelled residue (TRR) analysis: whole blood, plasma, liver, kidney,
skeletal muscle, subcutaneous fat, omental fat, perirenal fat, gastrointestinal tract and contents, and
carcass. Tissue samples were analysed for their TRR content using combustion analysis and LSC.
QUINOXYFEN X-X JMPR 2006