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Toxicological information

Acute Toxicity: oral

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Administrative data

Endpoint:
acute toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2007
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
This Fourteen Day Repeated Dose Oral Range-Finding study for the ‘Oral (Gavage) Reproduction/Development Toxicity Screening Test in the Rat’ was chosen to be the key study for the acute oral toxicity endpoint (Dhisa and Fulcher 2007). The study was conducted in accordance with the OECD TG 421 and TSCA OPPTS TG 870.3550, and with GLP standards (for full details see section 3.1.8) thus, it was rated klimisch 1.
Cross-reference
Reason / purpose for cross-reference:
reference to same study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2007

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
other: A preliminary Range finding test for the OECD Guideline 421 (Reproduction / Developmental Toxicity Screening Test)
Principles of method if other than guideline:
Sprague-Dawley Crl:CD® (SD) IGS BR strain rat were administrated oraly (gavage) with 1000, 500, 150 or 75 mg/kg/day of dibromomethane

GLP compliance:
yes
Test type:
fixed dose procedure
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:
Clear colourless liquid. 99.4%. purified dibromomethane

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals or test system and environmental conditions:
Fifteen male and fifteen female Sprague-Dawley Crl:CD® (SD) IGS BR rats, originally from Charles
River (UK) Limited, Margate, Kent and acclimatised to the laboratory conditions, were used for this
phase of the study. Animals were allocated to groups and given a unique number within the rangefinder
by ear punching. At the start of treatment the males weighed 339 to 412 g and the females
weighed 198 to 267 g.
The animals were housed in air-conditioned rooms within the Safepharm Laboratories Limited
Barrier Maintained Rodent Facility. The rate of air exchange was at least fifteen air changes per
hour and the low intensity fluorescent lighting was controlled to give twelve hours continuous
light and twelve hours darkness. Environmental conditions were continuously monitored by a
computerised system and print-outs of hourly mean temperatures and humidities are included in
the study records. The temperature and relative humidity controls were set to achieve target values
of 21±2ºC and 55 ±15% respectively.

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
polyethylene glycol
Remarks:
Polyethylene Glycol 400
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 an
adverse reaction to treatment at 1000 mg/kg/day, animals at these dosages were only dosed for three
consecutive days. Control animals and animals receiving 75, 150 or 500 mg/kg/day were dosed for
fourteen consecutive days. Animals receiving 75 mg/kg/day were added following the termination of
animals receiving 1000 mg/kg bw/day and treatment started for these animals three days after the
commencement of dosing for the other treatment groups.
Doses:
Dosages of 1000, 500, 150 or 75 mg/kg/day.
Due to an adverse reaction to treatment at 1000 mg/kg bw/day, animals at this dosage were only dosed for three consecutive days. Control animals and animals receiving 75, 150 or 500 mg/kg bw/day were dosed for fourteen consecutive days.
No. of animals per sex per dose:
Three male and three female rats per group
Control animals:
yes
Details on study design:
All animals were examined for overt signs of toxicity, adverse effects, behavioural change, and changes of bodyweights resulting from treatment. On completion of the treatment period, all animals were killed subjected to an internal and external macroscopic examination.
Statistics:
The following parameters were subjected to statistical analysis:
Bodyweight and bodyweight change
Food consumption during gestation and lactation

Results and discussion

Preliminary study:
n/a
Effect levels
Sex:
male/female
Dose descriptor:
LD50
Effect level:
> 1 000 mg/kg bw
Mortality:
None of the rats died during the study
Clinical signs:
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:
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.
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.
Gross pathology:
Treatment at 1000 mg/kg/day - macroscopic necropsy examination did not reveal any obvious cause for the decline in the
condition of the animals.
All animals at 75, 150 or 500 mg/kg/day survived to scheduled termination and necropsy examination did not reveal any affect of treatment at any of these dosages.

Applicant's summary and conclusion

Conclusions:
Since no deaths occurred in any of the dose levels tested, an LD50> 1000 mg/kg bw/day is concluded.
Executive summary:

The Fourteen Day Repeated Dose Oral Range-Finding study for the ‘Oral (Gavage) Reproduction/Development Toxicity Screening Test in the Rat’ was chosen to be the key study for the acute oral toxicity endpoint (Dhisa, N.K., and Fulcher, S. 2007). This study was conducted in accordance with the OECD TG 421 and TSCA OPPTS TG 870.3550, and with GLP standards (for full details see section 3.1.8) thus, it was rated klimisch 1. This range finding study was selected to represent the acute oral toxicity endpoint, in the absence of any other reliable source.

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 Sprague-Dawley Crl:CD® (SD) IGS BR strain rats. A control group of three male and three female rats was dosed with the vehicle (Polyethylene Glycol 400).

No deaths were observed in any of the groups. 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 at Day 4. This dosage was considered to be unsuitable for use in the main reproductive screening investigation and the therefore the animals were terminated on Day 4 of the study, having received three consecutive days doses of 1000 mg/kg/day. Macroscopic necropsy examination did not reveal any obvious cause for the decline in the condition of the animals.

Control animals and animals receiving 75, 150 or 500 mg/kg/day were dosed for fourteen consecutive days. There was no adverse effect on body weight gain at these doses. The incidence of clinical signs observed at 75, 150 or 500 mg/kg/day did not indicate any obvious adverse effect of treatment. All animals survived to scheduled termination (Day 14) and necropsy examination did not reveal any effect of treatment at any of these dosages.

Based on the results of this range finding study, an LD50> 1000 mg/kg/day is concluded.