Diquat dibromide

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

Sep 1990 to Dec 1990

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1991

Report date:

1991

Materials and methods

Objective of study:

distribution

excretion

metabolism

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 417 (Toxicokinetics)

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

6,7-dihydrodipyrido[1,2-b:1',2'-e]pyrazine-5,8-diium;dibromide;hydrate

Cas Number:

6385-62-2

Molecular formula:

C12H12N2.2Br.H2O

IUPAC Name:

6,7-dihydrodipyrido[1,2-b:1',2'-e]pyrazine-5,8-diium;dibromide;hydrate

Radiolabelling:

yes

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: males ca 50 days; females ca 60 days
- Housing: after dosing: plastic metabowls designed for the separate collection of urine and faeces
- Diet: standard laboratory diet, ad libitum
- Water: ad libitum
- Acclimation period: ca 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 ± 3
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
Radiolabelled [14C]-test substance (ca 24.7 MB) and non-radiolabelled test material monohydrate (1088.15 mg) were combined in aqueous solution (ca 25 g) in a plastic container. The concentration of radioactivity was measured and the specific activity was calculated to be 0.044 MBq/mg test material ion. Samples of the dose solution were weighed and analysed for total radioactivity. Individual doses were administered orally by gavage. The dose received by animals was assessed from the weight of the dose syringe and contents before administration and weight of dose syringe after administration.

Duration and frequency of treatment / exposure:

Single dose

Doses / concentrations

Dose / conc.:

1 mg/kg bw (total dose)

No. of animals per sex per dose / concentration:

5

Control animals:

no

Positive control reference chemical:

None

Details on dosing and sampling:

TOXICOKINETIC / PHARMACOKINETIC STUDY
- Following administration the rats were placed in plastic metabowls designed for the separate collection of urine and faeces.
- Tissues and body fluids sampled: urine, faeces, final cage wash
- Urine was collected at 8, 24, 36, 48, 72, 96, 120, 144 and 168 h post dose.
- Faeces were collected at 24, 48, 72, 96, 120, 144 and 168 h.
- Cages were rinsed at 24 h and daily thereafter, and a final cage wash was made after the last collection.
- Urine and faeces were collected into containers cooled with solid CO2 for the first 48 h post dose.
- At termination the animals were killed by CO2 narcosis an the following tissues, organs and body fluids were removed for analysis: bone, brain, testes/ovaries, stomach, stomach contents, small intestine, small intestine contents, large intestine, large intestine contents, plasma, whole blood, fat, heart, kidney, liver, lens, lungs muscle, spleen
- Total radioactivity was measured in urine, faeces, cage wash, tissues, organs, body fluids and remaining carcass.

Results and discussion

Main ADME results

Main ADME results 1

Type:

excretion

Results:

A mean of 85.5% of administered radioactivity was recovered in the faeces by 168 h post dose. Excretion via urine accounted for a mean of 5.4% of the dose administered. The mean total administered radioactivity recovered was 93.2%

Main ADME results 2

Type:

distribution

Results:

Total radioactivity in tissues, organs and body fluids was close to background. Highest levels were detected in the organs of excretion, kidney and liver (mean of 0.076 and 0.036 µg equiv /g respectively)

Main ADME results 3

Type:

metabolism

Results:

Radio-TLC analysis of pooled urine samples (0-48 h post dose; male and female separately) indicated the presence of a single major radiolabelled component of similar retention factor (Rf) to [14C]-test substance.

Main ADME results 4

Type:

metabolism

Results:

Radio-TLC analysis of extracts of pooled faeces (0-72 h post dose; male and female separately) indicated the presence of a single radiocomponent of a similar chromatographic character to [14C]-test substance

Toxicokinetic / pharmacokinetic studies

Details on absorption:

An oral dose of the test substance was apparently poorly absorbed in the rat. Following single oral administration of [14C]-test substance to rats at a target dose level of 186.8 mg/kg a mean of 5.4% of the administered radioactivity was recovered in the urine, and most of the radiolabelled material was recovered in faeces.

Details on excretion:

There was no sex difference in the pattern of excretion.

Metabolite characterisation studies

Metabolites identified:

no

Details on metabolites:

Radio-TLC analysis of pooled urine samples (0-48 h post dose; male and female separately) indicated the presence of a single major radiolabelled component of similar retention factor (Rf) to [14C]-test substance.
Radio-TLC analysis of extracts of pooled faeces (0-72 h post dose; male and female separately) indicated the presence of a single radiocomponent of a similar chromatographic character to [14C]-test substance

Any other information on results incl. tables

Table 1. Cumulative Excretion of Total Radioactivity in Excreta Following Single Oral Administration [14C]-test substance. Results expressed as % administered dose recovered

Sample/Time (h)	Males						Females
	1	2	3	4	5	Mean	1	2	3	4	5	Mean
Urine
0 – 8	0.77	1.62	1.13	0.9	1.04	1.09	1.05	1.27	1.18	0.72	1.31	1.11
0 – 24	1.91	3.24	3.28	2.74	3.56	2.94	2.07	2.68	4.62	2.21	2.41	2.79
0 – 36	2.69	4.59	4.37	4.06	3.74	3.89	2.92	3.34	5.75	3.15	3.02	3.64
0 – 48	3.12	9.27	5.22	4.9	4.03	5.31	4.12	3.88	7.94	4.5	3.44	4.78
0 - 72	3.25	10.75	5.3	5	4.07	5.57	4.29	4.01	8.09	4.57	4.16	5.02
0 - 98	3.27	10.78	5.31	5.01	4.07	5.59	4.32	4.03	8.13	4.59	4.28	5.07
0 – 120	3.28	10.79	5.32	5.02	4.07	5.7	4.33	4.04	8.15	4.6	4.37	5.1
0 – 144	3.28	10.80	5.33	5.02	4.07	5.7	4.35	4.04	8.15	4.6	4.39	5.11
0 – 168	3.28	10.80	5.33	5.02	4.07	5.7	4.35	4.04	8.15	4.6	4.4	5.11
Faeces
0 – 24	61.73	25.45	28.34	38.08	63.61	43.44	42.19	25.28	31.1	26.58	24.63	30.16
0 - 48	85.66	61.57	73.67	79.20	85.01	77.02	83.74	73.55	67.27	68.61	54.55	69.54
0 – 72	88.83	82.22	75.37	83.59	86.50	82.90	89.1	85.57	79.89	83.67	73.75	82.4
0 – 96	88.19	84.17	75.62	84.10	86.89	83.80	90.68	86.07	82.38	86.49	80.59	85.24
0 – 120	88.25	84.58	75.63	84.96	85.95	84.08	91.1	86.11	82.92	86.62	86.12	86.57
0 – 144	88.27	84.69	75.65	84.97	86.99	84.11	91.28	86.13*	83	86.65	86.9	86.79
0 – 168	88.45	84.75	75.65	84.97	87.04	84.17	91.29	86.15	83.01*	86.67	87.05	86.83
Cage wash
0 – 24	0.28	0.83	8.7	1.39	1.54	2.55	0.81	1.37	3.94	0.45	0.39	1.39
0 - 48	0.39	1.1	8.92	1.48	1.62	2.7	0.89	1.54	4.01	0.56	0.56	1.52
0 – 72	0.41	1.28	8.97	1.63	1.63*	2.78	0.93*	1.6	4.07	0.63*	0.67	1.58
0 – 96	0.45*	1.28**	8.98**	1.64*	1.64**	2.80	0.95**	1.61**	4.10*	0.67	0.7*	1.61
0 – 120	0.45**	1.28**	8.98**	1.54**	1.64**	2.80	0.95**	1.61**	4.10**	0.67**	0.75	1.62
0 – 144	0.45**	1.28**	8.98**	1.64**	1.64**	2.80	0.95**	1.61**	4.10**	0.68**	0.77*	1.62
0 – 168	0.46**	1.32	8.98**	1.66**	2.08	2.9	1	1.66	4.2	0.73	0.95	1.71
Total excreta
0 – 8	1.05	2.45	9.83	2.29	2.57	3.64	1.86	2.64	5.12	1.17	1.7	2.5
0 – 24	63.91	29.52	40.32	42.21	68.7	48.93	45.07	30.31	39.66	29.24	27.43	34.34
0 – 36	64.69	30.87	41.41	43.53	68.88	49.88	45.92	30.99	40.79	30.18	28.04	35.18
0 – 48	89.17	71.94	87.81	85.58	90.66	85.03	88.75	78.98	79.22	73.7	58.55	75.84
0 – 72	90.49	94.25	89.64	90.22	92.2	91.36	94.32	91.18	92.05	88.87	78.58	89
0 – 96	91.91	96.23	89.91	90.75	92.61	92.28	95.95	91.71	94.61	91.75	85.57	91.92
0 – 120	91.98	96.65	89.93	91.62	92.68	92.57	96.38	91.76	95.17	91.89	91.24	93.29
0 – 144	92	96.77	89.96	91.63	92.71	92.62	96.58	91.78	95.25	91.93	92.06	93.52
0 – 168	92.19	96.87	89.96	91.65	93.2	92.78	96.64	91.85	95.36	92.01	92.4	93.65
Tissues	0	0	0	0	0	0	0	0	0	0	0	0
Carcass	0.03**	0**	0.04**	0.03**	0.01**	0.02	0**	0**	0.02**	0.01**	0**	0.01
Total recovered	92.22	96.87	90	91.68	93.21	92.78	96.64	91.85	95.38	92.02	92.40	93.66

* results derived from data <30 d.p.m. above background

** results derived from data <10 d.p.m above background

Applicant's summary and conclusion

Conclusions:

An oral dose of diquat was apparently poorly absorbed in the rat. Following single oral administration of the [14C]-test substance to rats at a target dose level of 100 mg/kg test substance a mean of 5.4% of administered radioactivity was recovered in urine, and most of the radiolabelled material was recovered in faeces. The relatively low levels of radioactivity in tissues tat 168 h post dose and the presence of parent compound in extracts of pooled faeces are consistent with limited absorption of the test substance. the chromatographic profiles of pooled urine samples indicated that the low proportion of radiolabelled material absorbed is excreted unmetabolized.
A mean of 73.3% of administered radioactivity was recovered in the faeces by 48 h; by 168 h post dose the mean faecal recovery was 85.5%. Excretion by the urinary route accounted for 5.4% of the administered dose by 168 h. The mean total dose recovered was 93.2%. At 168 h post dose levels of radioactivity in tissues, organs and body fluids were at, or close to, background.

Executive summary:

This report describes aspects of the elimination of [14C]-test substance in the rat following single oral administration at a target dose level of 186.8 mg/kg. Radioactivity was predominantly excreted via faeces. A mean of 73.3% of administered radioactivity was recovered in the faeces by 48 h; by 168 h post dose the mean faecal recovery was 85.5%. Excretion by the urinary route accounted for 5.4% of the administered dose by 168 h. The mean total dose recovered was 93.2%. At 168 h post dose levels of radioactivity in tissues, organs and body fluids were at, or close to, background. No apparent sex difference was observed in the pattern of excretion. Radio-TLC analysis of pooled urine samples indicated the presence of a single major radiocomponent which co-chromatographed with [14C]-test substance. A similar component was observed in the extract of pooled faeces samples.