Pesticide residues in food — 2007: Toxicological ... - ipcs inchem

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higher renal excretion in the group receiving a single lower dose. In the group receiving multiple
lower doses, excretion via the urine amounted to approximately 60% and via faeces was nearly 30%.
More details are presented in Table 1. Biliary excretion of aminopyralid was assumed to be very low,
on the basis of studies with the closely-related substances triclopyr, picloram, fluroxypyr and 2,4-D.
Therefore, the company did not perform experiments to analyse the biliary excretion of aminopyralid
and the percentage of absorbed material was calculated as the sum of the renally excreted and residual
substance in the tissues and the carcass. On this basis, the percentage of absorbed material was
estimated to be 42%, 50% and 59% for the groups receiving the single higher dose, the single lower
dose and multiple lower doses, respectively.
The urinary elimination was biphasic, with elimination half-lives t 1/2α
and t 1/2β
of 3–4 h and
10–12 h, respectively (see Table 2). For both half-lives, there were no significant differences between
the three dosing groups, 74.0–93.1% of the administered dose being excreted within the first 24 h
after dosing.
As can be seen from Table 3, after a depletion period of 168 h, virtually all of the examined tissues
had radioactivity levels of less than 0.01% of the administered dose. Only in the skin of the rats
in the group receiving a single higher dose were notable levels detected, but with high interindividual
variability (1–66 μg eq/g).
Pooled samples of urine from 0–6 h and 6–12 h, together contained 78–90% of the total
radioactivity recovered in the urine and in all dose groups unchanged aminopyralid comprised more
than 96% of the radiolabel present. The remainder of the radiolabel in the urine, approximately 4%,
Table 1. Recovery of radioactivity over 7 days in rats given radiolabelled aminopyralid by gavage
Sample
Recovery (% of administered dose)
1000 mg/kg bw
(single dose)
50 mg/kg bw (single dose) 50 mg/kg bw per day
(rpeat dose)
Urine 41.3 ± 8.6 49.8 ± 4.8 58.65 ± 5.5
Faeces 43.4 ± 7.7 43.1 ± 5.8 33.0 ± 4.6
Volatiles 0.01 ± 0.00 NA NA
Cage wash 9.7 ± 3.1 3.0 ± 0.9 3.4 ± 0.7
Tissues/carcass 0.73 ± 0.72 0.07 ± 0.04 0.09 ± 0.02
Total recovery 95.2 ± 10.5 96.0 ± 1.7 95.0 ± 1.8
Absorbed material 42 50 59
From Liu (2004)
NA, not applicable, no collection performed.
Table 2. Average urinary elimination half-lives in rats given radiolabelled aminopyralid by gavage
Urinary elimination
half-life (h)
Dose
1000 mg/kg bw
(single dose)
50 mg/kg bw
(single dose)
50 mg/kg bw per day
( repeat dose)
t1/2α 3.8 ± 0.5 2.9 ± 1.2 3.3 ± 0.7
t1/2β 10.9 ± 2.7 10.2 ± 3.3 12.3 ± 3.7
From Liu (2004)
AMINOPYRALID 3–36 JMPR 2007