Registration Dossier

Administrative data

acute toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
23. 7. 91- 22. 9. 92
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study

Data source

Reference Type:
study report

Materials and methods

Test guideline
equivalent or similar to guideline
OECD Guideline 401 (Acute Oral Toxicity)
not specified
GLP compliance:
Test type:
standard acute method
Limit test:

Test material

Constituent 1
Chemical structure
Reference substance name:
EC Number:
Cas Number:
Molecular formula:
Specific details on test material used for the study:
45W81 (2-bromo-6-(4-toluoyl)-pyridine)
Batch 310/C60

Test animals

Details on test animals or test system and environmental conditions:
Twelve male and twelve female Wistar (VAF) rats, approximately 7 weeks of age and in the weight range 150-2489 on Day 1 study were supplied by Charles River UK Ltd, Manston, Kent. The rat is a conventionally accepted laboratory animal used for safety testing. The animals were housed in Room 4, Building 88, East Wing, under standard environmental conditions. The rats were allowed to acclimatise for approximately 14 days prior to the start of dosing. The rats were allocated, 3 males and 3 females per group, following a routine randomisation procedure, and housed 3 of one sex per cage.

Each animal was identified by ear punch and a within cage system of colour marking on the head .

Pelleted diet (PCD, Special Diet Services, batch 5921 and 6103) and tap water (Bore hole or Thames Water Authority) were provided ad libitum. Tap water from Thames Water Authority was used from Day 8 of the study due to contamination of the Bore hole water with Pseudomonas. This is not thought to have affected the integrity of the study.

No known contaminants were present in the diet which were likely to have affected the study.

Administration / exposure

Route of administration:
oral: gavage
Details on oral exposure:
1% w/v aqueous methyl cellulose (Sigma Chemical Company) Batch 57F 0522 was used as the vehicle.

Suspensions of 45W81 were prepared by the Drug Formulation Laboratory, Drug Safety Evaluation, Beckenham. Dosing suspensions were prepared in vehicle to give final concentrations of 200 and 50mg/ml. Further dosing suspensions of 100, or 150mg/ml were prepared by dilution in vehicle on the day of dosing. No analysis for 45W81 content was performed due to the lack of a suitable validated method.

Doses were administered orally once only by gavage at a volume to bodyweight ratio of 10ml/kg.
Dose Groups
Group 1 (M1, F5) - 500mg/kg (50mg/ml)
Group 2 (M2, F6) - 1000mg/kg (100mg/ml)
Group 3 (M3, F7) - 1500mg/kg (150mg/ml)
Group 4 (M4, F8) - 2000mg/kg (200mg/ml)

Animals in Groups 1 and 2 were dosed on Day 1, group 3 animals on Day 2 and group 4 animals on Day 3. Food was removed from all groups overnight prior to dosing.
No. of animals per sex per dose:
1 male and 1 female per dose
Control animals:
Details on study design:
Clinical Signs
All animals were observed for signs of ill health prior to dosing, at intervals after dosing on Day 1, and twice daily until Day 15, according to stagger.

Individual bodyweights were recorded on Days 1, 2, 8 and 15 according to stagger.

Terminal Procedures
All rats were killed by intraperitoneal injection of sodium pentobarbitone (Euthatal). A full macroscopic examination (excluding the CNS) was performed and the lungs from two female animals dosed at 500mg/kg were taken for histological examination.

Results and discussion

Effect levels
Key result
Dose descriptor:
Effect level:
> 2 000 mg/kg bw
Based on:
test mat.
There were no unscheduled deaths.
Clinical signs:
Clinical signs of hypothermia, hunched posture, piloerection, decreased food consumption, emaciation and a paddling action of the forelimbs were noted in some group 2 (1000mg/kg) animals. Group I (500mg/kg) and group 2 animals showed a reduction in faecal production, dark coloured faeces and a high stepping gait. Other clinical signs observed were considered not to be treatment-related.
Body weight:
Group 3 (1500mg/kg) animals of both sexes showed an initial decrease in bodyweight between Days I and 2. Animals in groups 2 and 4 showed a decreased bodyweight gain between Days 1 and 2.
At termination of the study, the bodyweights of all male groups were similar as were the bodyweights of all female groups.
Gross pathology:
Small dark red discoloured foci of up to Imm diameter were noted in the lungs of two female group I animals macroscopically. Microscopically, minimal hyperaemia (912439, 912438) and alveolar haemorrhage (912438) were present. These lesions were not treatment-related.

Applicant's summary and conclusion

Oral administration of 45W81 to male and female Wistar rats at doses of 500, 1000, 1500 or 2000mg/kg produced a variety of clinical signs in animals dosed at 500 and 1000mg/kg. The significance of the clinical signs observed in these animals were not clear as similar signs were not seen in animals given 1500 or 2000mg/kg.
The acute lethal dose of 45W81 in the Wistar rat was greater than 2000mg/kg.