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Repeated dose toxicity: oral

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Administrative data

Endpoint:
short-term repeated dose toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
This study was conducted in accordance with the OECD test guideline 421 and according to GLP standards. Thus, even though these are not the direct guidelines for testing repeated dose oral toxicity, the range finding test was found sufficiently reliable to imply on toxic effects of dibromomethane following repeated administration to rats for 14 days.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Report date:
2007

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
other:
Principles of method if other than guideline:
A preliminary Range finding test for the OECD Guideline 421 (Reproduction / Developmental Toxicity Screening Test)
GLP compliance:
yes (incl. QA statement)
Limit test:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
Dibromomethane
EC Number:
200-824-2
EC Name:
Dibromomethane
Cas Number:
74-95-3
Molecular formula:
CH2Br2
IUPAC Name:
dibromomethane
Details on test material:
99.4% purity, DBM, Clear colourless liquid.

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals or test system and environmental conditions:
24 animals (three male and three female rats per group), Sprague-Dawley Crl:CD® (SD) IGS BR strain.
Males weighed 339 to 412 g. Females weighed 198 to 267 g at the star of the study.
Animals were housed 3 per cage with environmental enrichment, and water access throughout the study.
Room temperature was 21 ± 2ºC, and relative humidity was 55 ± 15%.


Administration / exposure

Route of administration:
oral: gavage
Vehicle:
polyethylene glycol
Details on oral exposure:
The test material was administered daily by gavage using a suitable dosing cannula attached to a
disposable plastic syringe at a dosage volume of 4 ml/kg bodyweight.
Control animals were treated in an identical manner, receiving vehicle (Polyethylene Glycol 400) at the same volume dosage.

Due to anadverse reaction to treatment at 1000 mg/kg/day, animals at these dosages were only dosed for threeconsecutive days.
Control animals and animals receiving 75, 150 or 500 mg/kg/day were dosed for 14 consecutive days.
Duration of treatment / exposure:
14 days
Frequency of treatment:
Daily
No. of animals per sex per dose:
3 rats
Details on study design:
dose of 0, 75, 150, 500, 1000 mg/kg/day
Positive control:
None

Examinations

Observations and examinations performed and frequency:
Mortality:
Animals were examined for signs of ill health twice daily, early and late during the working period, thought the study. Animals at 1000mg/kg/day killed on day4 due to the early termination of this dosage group were subjected to full macroscopic necropsy.

Clinical signs:
All animals were examined for signs of toxicity, ill health or behavioural change immediately before and after dosing and one hour after dosing. All observations were recorded.

Bodyweight:
Individual bodyweights were recorded on Days 1, 4, 8 and 15 of the treatment period.

Necropsy:
On completion of the treatment period, all animals were killed by cervical dislocation and immediately subjected to an internal and external macroscopic examination. No tissues were retained.

Evaluation of the data:
Clinical observations, bodyweights, bodyweight change and necropsy data were examined for any adverse effects resulting from treatment. The data obtained were used to provide the basis for selection of dose levels for the main study. In view of the preliminary nature of this phase of the study and the small group size no statistical analyses were performed.
Sacrifice and pathology:
On completion of the treatment period, all animals were killed by cervical dislocation and immediately subjected to an internal and external macroscopic examination. No tissues were retained.
Statistics:
In view of the preliminary nature of this phase of the study and the small group size no statistical analyses were performed.

Results and discussion

Results of examinations

Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
None of the rats died during the range finding study. Treatment at 1000 mg/kg/day was associated with notable bodyweight loss and a decline in the clinical condition of all three males on Day 4 of the study. One male showed ataxia and piloerection and the other two males showed hunched posture; all three males also showed red/brown staining around the eyes. One female at 1000 mg/kg/day also showed ataxia and red/brown staining around the eyes and a slight bodyweight loss on Day 4. No clinical signs were apparent for the remaining two females at this dosage and there was no obvious adverse effects of treatment on bodyweight gain of these animals to Day 4. The incidence of clinical signs observed at 75, 150 or 500 mg/kg/day did not indicate any obvious adverse effect of treatment.
Mortality:
mortality observed, treatment-related
Description (incidence):
None of the rats died during the range finding study. Treatment at 1000 mg/kg/day was associated with notable bodyweight loss and a decline in the clinical condition of all three males on Day 4 of the study. One male showed ataxia and piloerection and the other two males showed hunched posture; all three males also showed red/brown staining around the eyes. One female at 1000 mg/kg/day also showed ataxia and red/brown staining around the eyes and a slight bodyweight loss on Day 4. No clinical signs were apparent for the remaining two females at this dosage and there was no obvious adverse effects of treatment on bodyweight gain of these animals to Day 4. The incidence of clinical signs observed at 75, 150 or 500 mg/kg/day did not indicate any obvious adverse effect of treatment.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
Treatment at 1000 mg/kg/day was associated with notable bodyweights loss and a decline in clinical conditions of all 3 males on Day 4. No effects on bodyweight gain at dosages of 75, 150 or 500mjg/kg/day.
Food consumption and compound intake (if feeding study):
not specified
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
not specified
Haematological findings:
not specified
Clinical biochemistry findings:
not specified
Urinalysis findings:
not specified
Behaviour (functional findings):
not specified
Organ weight findings including organ / body weight ratios:
not specified
Gross pathological findings:
no effects observed
Description (incidence and severity):
Macroscopic necropsy examination did not reveal any obvious cause for the decline in the condition of the animals.
Histopathological findings: non-neoplastic:
not specified
Histopathological findings: neoplastic:
not specified
Details on results:
At 1000 mg/kg/day:
Treatment at 1000 mg/kg/day was associated with notable bodyweight loss and a decline in the clinical condition of all three males on Day 4 of the study. One male showed ataxia and piloerection and the other two males showed hunched posture; all three males also showed red/brown staining around the eyes. One female at 1000 mg/kg/day also showed ataxia and red/brown staining around the eyes and a slight bodyweight loss on Day 4. No clinical signs were apparent for the remaining two females at this dosage and there was no obvious adverse effects of treatment on bodyweight gain of these animals to Day 4.
This dosage was considered to be unsuitable for use in the main reproductive screening investigation and therefore the animals were terminated on Day 4 of the study, having received three consecutive daily doses. Macroscopic necropsy examination did not reveal any obvious cause for the decline in the condition of the animals.

At 75, 150 and 500 mg/kg/day:
The incidence of clinical signs observed at 75, 150 or 500 mg/kg/day did not indicate any obvious adverse effect of treatment. At 500 mg/kg/day, red staining of the cage tray paper was observed for males during Days 7-10; the significance of this observation is unclear but, as it did not persist and was not associated with any decline in the condition of the animals, it was considered not to preclude this dosage from further investigation.
There was no adverse effect of treatment on bodyweight gain at dosages of 75, 150 or 500 mg/kg/day.
An initial bodyweight loss to Day 4 was apparent for one male and one female at 150 mg/kg/day, although an initial loss was not apparent for the remaining animals at this dosage or for either sex at 500 mg/kg/day. Isolated incidences of bodyweight loss were observed for a few treated animals during the remainder of the study but were considered to reflect normal biological variation rather than an adverse effect of treatment.

Effect levels

Dose descriptor:
NOAEL
Effect level:
ca. 500 other: mg/kg bw/day

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
At dosage of 1000 mg/kg/day adverse effect on bodyweight and the clinical condition of the animals was seen, particularly males.Therefore,
was considered to be too high for use in the main reproductive screening investigation. Dosages of up to 500 mg/kg/day were considered to be well tolerated by both sexes.

A NOTE: This study was conducted in accordance with the OECD test guideline 421 and according to GLP standards. Thus, even though these are not the direct guidelines for testing repeated dose oral toxicity, the range finding test was found sufficiently reliable to imply on toxic effects of DBM following repeated administration to rats for 14 days.
Executive summary:

Sprague-Dawley Crl:CD® (SD) IGS BR strain rats were housed in groups of three by sex. Dosages of 1000, 500, 150 or 75 mg/kg/day of the test material (99.4% purity, dibromomethane) were administered by gavage to groups consisting of three male and three female rats. A control group of three male and three female rats was dosed with the vehicle (Polyethylene Glycol 400).

All animals in the 75, 150, and 500, mg/kg/day groups survived to scheduled termination and at necropsy were not observed to have treatment related effects. Animals dosed at 1000 mg/kg/day showed adverse effects on body weights and clinical conditions (particularly males) and were sacrificed after three days of exposure. Top dose chosen for the reproduction screening test was 500 mg/kg/day. There were no significant treatment-related clinical signs of repeated toxicity observed up to 500 mg/kg/day in a Preliminary Fourteen Day Repeated Dose Oral Range-Finding study.