Benzyl 4-[(1-butyl-5-cyano-1,6-dihydro-2-hydroxy-4-methyl-6-oxopyridin-3-yl)azo]benzoate

Endpoint summary

Description of key information

LD₅₀ (oral, rats) > 5000 mg/kg bw

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

24 July to 13 August, 1987

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 401 (Acute Oral Toxicity)

Version / remarks:

1981

GLP compliance:

yes

Test type:

standard acute method

Limit test:

yes

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Interfauna (UK) Limited, Wyton, Huntingdon, Cambridgeshire, UK
- Age at study initiation: 5 to 8 weeks old
- Weight at study initiation: males: 125 - 150 g; females: 122 - 150 g
- Fasting period before study: overnight until 2 hours after dosing
- Housing: groups of 5 by sex in solid floor polypropylene cages with sawdust bedding
- Diet: ad libitum; Rat and Mouse Expanded Diet No. 1, Special Diet Services Limited, Witham, Essex, UK
- Water: ad libitum
- Acclimation period: minimum 5 days

ENVIRONMENTAL CONDITIONS
- Temperature: 19 - 22 °C
- Relative humidity: 65 - 70 %
- Air changes: 15 per hour
- Photoperiod (hrs dark / hrs light): 12/12, controlled by a time switch

Route of administration:

oral: gavage

Vehicle:

water

Remarks:

distilled

Details on oral exposure:

- Preparation: the test item was ground to a fine powder using a mortar and pestle and freshly prepared as required at the appropriate concentrations in distilled water. Identification and stability of the test item were not determined.
- Administration: oral gavage using a metal cannula attached to a graduated syringe

Doses:

- Dose volume: 10 ml/kg based on fasted body weight at dosing
- Dosage of range-finding study: 2000 and 5000 mg/kg bw
- Dosage of main study: 5000 mg/kg bw

No. of animals per sex per dose:

- Range-finding study: 1 male and 1 female per dose (two doses studied; total = 4 animals)
- Main study: 5 males and 5 females (total = 10 animals)

Control animals:

no

Details on study design:

RANGE-FINDING STUDY
- Duration of observation period following administration: 5 days
- Observations: mortality and overt toxicity
- Frequency of observations: 1 and 4 hours after administration, then daily up to 5 days
- Necropsy of survivors performed: no

MAIN STUDY
- Duration of observation period following administration: 14 days
- Observations: mortality, overt toxicity, clinical observations, bodyweight, post-mortem examination
- Frequency of observations: 1 and 4 hours after administration, then daily up to 5 days
- Frequency of weighing: days 0, 7 and 14
- Necropsy of survivors performed: yes

Preliminary study:

For the five days following oral administration, no mortality was observed at either dose. Using the mortality data, the LD50 of the test item was predicted to be greater than 5000 mg/kg bw, hence this dose was selected for the main study.
The high-dose and low-dose males both demonstrated hunched posture, lethargy, piloerection and decreased respiratory rate at 1 hour post dosing, and the high-dose and low-dose females both demonstrated hunched posture and piloerection at this time point.
All four animals continued to demonstrate hunched posture and piloerection at four hours after administration; no symptoms were observed at 24 hours after adminstration until the end of the test.

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 5 000 mg/kg bw

Based on:

test mat.

Mortality:

No mortality was observed among either male or female rats at the dose tested.

Clinical signs:

No signs of systemic toxicity were noted during the study period.

Body weight:

All animals showed expected gains in bodyweight over the study period.

Gross pathology:

No abnormalities were noted at necropsy of animals killed at the end of the study period.

Interpretation of results:

other: not classified according to the CLP Regulation (EC 1272/2008)

Conclusions:

The LD50 of test item to male and female rats was found to be greater than 5000 mg/kg bw.

Executive summary:

The acute oral toxicity of the test item to male and female Sprague-Dawley rats was evaluated in an experimental study according to the OECD guideline 401 (1981). In a preliminary dose-range finding study, one male and one female were administered 5000 mg/kg bw by oral gavage, and additionally one male and one female were administered 2000 mg/kg bw. All four animals were monitored for mortality and overt toxicity for 5 days (1 and 4 hours then daily). No mortality/overt toxicity was observed, hence the higher dose was selected for the main study.

In the main study, 5 males and 5 females were dosed 5000 mg/kg bw and monitored for mortality and clinical signs at 1 and 4 hours then daily until 14 days, after which time all surviving animals were sacrificed and subjected to necropsy. Body weights were monitored on test days 0, 7 and 14. No mortality occurred; based on mortality, the LD₅₀ value for the test item was found to be greater than 5000 mg/kg bw. No clinical signs, unexpected bodyweight changes or abnormal necropsy findings were noted.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Acute toxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Acute toxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

The acute oral toxicity of the substance was evaluated using three in vivo experimental studies on rats according to the OECD guideline 401 (1981), or equivalent. The key study was chosen based on the purity of the test sample and the test procedure, e.g. guideline available and GLP.

Details are available:

KS - limit test without control animals; no mortality among the 5 male and 5 female animals receiving 5000 mg/kg bw; no signs of systemic toxicity were observed.

SS- limit test with controls; no mortality among the 5 male and 5 female treatment animals receiving 15 g/kg bw or the 5 male and 5 female control animals; sypmtoms (piloerection, hunched posture, waddling, lethargy and diarrhoea) occurred in all treatment animals, and additionally decreased respiratory rate, ptosis and pallor of the extremities in two males and two females, and piloerection in some controls. All symptoms were reversible within 6 days.

SS - no mortality among animals administered either 3000, 4000 or 5000 mg/kg bw in groups of 5 male and 5 female animals without controls; slight yet dose dependent symptoms (dyspnoea, sedation, curved body posure and ruffled fur occurred) occurred up to day 7, however, were reversible.

Justification for classification or non-classification

In the CLP Regulation (EC 1272/2008), acute toxicity is defined as “those adverse effects occurring following oral or dermal administration of a single dose of a substance or a mixture, or multiple doses given within 24 hours, or an inhalation exposure of 4 hours”. A substance can be allocated to one of four toxicity categories based on acute toxicity by the oral, dermal or inhalation route. The numeric criteria based on the acute toxicity estimates (ATE) in mg/kg bodyweight are presented in Annex I, Part 3, Table 3.1.1. For acute oral toxicity: "Category 4: 300 < ATE ≤ 2000", and substances with an ATE of greater than 2000 mg/kg bw are not classified.

Based on the results of the in vivo experimental studies performed on rats, the acute toxicity estimate (ATE) of the substance is greater than 2000 mg/kg body weight. Therefore, no classification is needed.