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

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0.5% tragacanth orally by gavage, while an additional group of five male rats received a single dose
at 100 mg/kg bw. For measurement of radioactivity in expired air, a further test group of five male
rats received a single oral dose of 1 mg/kg bw. Faeces, urine, plasma and expired carbon dioxide
were collected for up to 48 h, when the animals were sacrificed. A commercial computer programme
(TOPFIT) was used to analyse the plasma curves and calculate the pharmacokinetic parameters.
Plasma concentrations of radioactivity indicated the rapid absorption of thiacloprid (Table 5).
Maximum plasma concentrations were attained at 2–3 h (lowest dose) and at 4 h (highest dose). Plasma
concentrations of radioactivity also indicated the rapid distribution and elimination of thiacloprid at the
lowest dose. Slower rates of absorption and excretion were seen at the highest dose, with significant
plasma concentrations of radioactivity at 48 h. The large Vd suggested the rapid distribution of thiacloprid
into tissues. The relatively small MRT indicated that redistribution into plasma before excretion was
also rapid.
Table 5. Plasma concentrations and kinetic parameters of 14 C-thiazolidine-labelled thiacloprid in
rats
Time-point
Mean plasma concentrations of radiolabelled thiacloprid (μg/kg equivalent)
1 mg/kg 100 mg/kg
Males Females Males
5 min 0.11 0.07 1.46
10 min 0.23 0.19 5.75
20 min 0.43 0.35 13.07
40 min 0.57 0.51 25.38
1 h 0.64 0.58 32.94
1.5 h 0.65 0.64 35.49
2 h 0.66 0.66 32.34
3 h 0.58 0.69 39.04
4 h 0.55 0.68 50.34
6 h 0.42 0.59 33.07
8 h 0.32 0.48 34.84
24 h 0.07 0.07 23.16
32 h 0.05 0.04 25.15
48 h 0.03 0.02 10.38
Kinetic parameters
Vd (ml/kg bw) 1450 1720 700
Cl (ml/min × kg bw) 1.82 1.60 1.07
t ½
(h) a 2.2/19.0 3.3/44.5 4.0/9.9
AUC (μg/ml × h) 9.19 10.4 1560
MRT (h) 16.5 22.8 25.3
From Printz & Bornatsch (1997)
AUC, area under the curve; Cl, clearance; MRT, mean residence times; Vd, volume of distribution.
a
Half-lives for first elimination phase and for terminal elimination phase.
Radioactivity was excreted primarily in the urine (60.2–82.9%) and largely during the
first 24 h after oral administration (Table 6). Faecal excretion was also significant (13.3–18.6%).
Excretion of radiolabelled carbon dioxide in expired air was found to be minimal (0.86%).
THIACLOPRID X-X JMPR 2006