4'-methoxyacetoacetanilide

Endpoint summary

Description of key information

KEY STUDY (KEY_401_1997_Inveresk_14820), LD50 female rat (= most sensitive sex): 1755 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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Well performed GLP and OECD guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 401 (Acute Oral Toxicity)

Deviations:

no

GLP compliance:

yes

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan Olac Ltd, Shaw's Farm, Blackthorn, Bicester
- Age at study initiation: 5-7 weeks old
- Weight at study initiation:
-- male , mean: 192 g
-- female, mean: 156 g
- Fasting period before study: overnight prior to dosing
- Housing: in suspended polypropylene cages with stainless steel grid tops and bottoms
- Diet (e.g. ad libitum): Rat and Mouse No. 1 Maintenance Diet, supplied by Special Diets Services, 1 Stepfield, Witham, Essex, CM8 3AD, ad libitum
- Water (e.g. ad libitum): Domestic mains quality drinking water, ad libitum
- Acclimation period: for at least 5 days prior to commencement of the study

ENVIRONMENTAL CONDITIONS
- Temperature (°C): maximum/minimum 20°C / 19°C
- Humidity (%): Although the mean humidity is outwith the range specified in the protocol, 55 % ± 15 %, it is considered not to have affected the outcome of the study.
- Air changes (per hr): 15-20 air changes per hour
- Photoperiod (hrs dark / hrs light): 12 h light/dark cycle

Route of administration:

oral: gavage

Vehicle:

CMC (carboxymethyl cellulose)

Remarks:

0.5%

Details on oral exposure:

VEHICLE

- Concentration in vehicle:

Dose level / Conc.
1250 / 125 mg/ml
1500 / 150 mg/ml
1750 / 175 mg/ml
2000 / 200 mg/ml

- Amount of vehicle (if gavage): 10 ml/kg bw

Doses:

1250, 1500, 1750 and 2000 mg/kg bw.

No. of animals per sex per dose:

4 groups of 5 male and 5 female rats were dosed

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days

- Frequency of observations and weighing:
-- Body weights were recorded weekly
-- Animals were observed daily up to 14 days

- Necropsy of survivors performed: yes

- Other examinations performed:
-- clinical signs: yes
-- body weight: yes
-- organ weights: no
-- necropsy: yes

Statistics:

The intercept and slope values of the dose-response curve and hence the LD50, was estimated by applying the standard technique of maximum likelihood estimation to the probit model, as described in Finney (1971)

Sex:

male

Dose descriptor:

LD50

Effect level:

1 941 mg/kg bw

Based on:

test mat.

Sex:

female

Dose descriptor:

LD50

Effect level:

1 755 mg/kg bw

Based on:

test mat.

Mortality:

Dose / male / female
level

1250 / 0 of 5 / 0 of 5
1500 / 1 of 5 / 1 of 5
1750 / 1 of 5 / 1 of 5
2000 / 3 of 5 / 5 of 5

Clinical signs:

other: Clinical signs noted from Day 1 included ataxia, subdued behaviour, piloerection, prostration, tremors, hunched appearance, laboured breathing, increased salivation and a red discharge from the eyes and/or nose. Generally, the surviving animals recovered

Gross pathology:

None of the necropsy findings were considered to be related to treatment.

Interpretation of results:

Toxicity Category IV

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

Under the conditions of the study, the median oral lethal doses (LD50s) for the test item in rats were estimated to be:
Males: 1941 mg/kg bw
Females: 1755 mg/kg bw
Males and Females: 1830 mg/kg bw

These findings meet criteria for a classification as acutely toxic according to REGULATION (EC) No 1272/2008:

Acute oral toxicity: Category 4

Executive summary:

This study investigated the acute oral toxicity potential and median oral lethal dose (LD50) of the test substance, after a single oral gavage administration to rats.

 

In the study, 4 groups of 5 male and 5 female rats were dosed with 1250, 1500, 1750 and 2000 mg/kg bw. Dosing solutions were administered via oral gavage at a dose volume of 10 ml/kg bw. The vehicle was 0.5% Carboxymethylcellulose. The animals were observed daily for reaction to treatment for up to 14 days after dosing. Following premature death or sacrifice, on Day 15, the animals were subjected to necropsy. Body weights were recorded weekly.

 

At 1250 mg/kg bw there were no premature decedents, at 1500 mg/kg bw, one male was found dead on Day 2 and 1 female was killed humanely on Day 2. At 1750 mg/kg bw, one male and 1 female were found dead on Day 2 and at 2000 mg/kg bw, one male was found dead on Day 1, and another 2 males were killed humanely, one on Day 1 and another on Day 2, all 5 females were killed humanely, three on Day 1 and two on Day 2.

 

Clinical signs noted from Day 1 included ataxia, subdued behaviour, piloerection, prostration, tremors, hunched appearance, laboured breathing, increased salivation and a red discharge from the eyes and/or nose. Generally, the surviving animals recovered by Day 4.

 

Body weight performance was considered to have been satisfactory.

 

None of the necropsy findings were considered to be related to treatment.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

1 755 mg/kg bw

Quality of whole database:

reliable

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

Discussion of classification or non-classification

 

Testing of p-acetoacetanisidide for acute oral toxicity revealed an LD50 value of 1755 mg/kg bw. Acetoacetanisidid congeners are suspected to form methemoglobin in man. The absence of definite indications for MetHb formation in this study might be attributed to the relative insensitivity of the rat to methemoglobinaemia inducing toxicants as compared to cat or man. Therefore and following precautionary principles p-acetoacetanisidide is assumed to be a MetHb forming agent in man.

Read across hypothesis / justification

The purpose of this assessment is to provide justification for read across in order to predict the skin sensitizing potential and MetHb forming properties of the target substance p-acetoacetanisidide (5437-98-9) based on available date coming from the source substances o-acetoacetanisidide (92-15-9).

Source and target substance are position isomeric acetoacetanisidides without any other structural differences. Both substances are characterized by similar physical-chemical properties and available data show a consistent toxicity profile. Therefore, it can reasonably be assumed, that acute toxicity, MetHb forming properties and the possible skin sensitizing potential of p-acetoacetanisidide and o-acetoacetanisidide are likely to be similar.

Data Matrix

	Target Chemical	Source Chemical
CAS #	5437-98-9	92-15-9
CHEMICAL NAME	p-acetoacetanisidide	o-acetoacetanisidide
Other name	4'-methoxyacetoacetanilide N-Acetoacetyl-p-anisidine	2’-methoxyacetoacetanilide N-Acetoacetyl-o-anisidine
Structure	Not displayed	Not displayed
Physical and chemical properties
Purity	99.4 %	99.86 % (w/w)
Physical state	solid	solid
Melting point	116°C	82°C
Decomposition Temp.	>450°C	>450°C
Density	1.242 g/cm^3	1.31 g/cm^3
Vapour pressure (calculate)	< 0.001 Pa at 20°C	0.000036 Pa at 20°C
Log Pow (at 23°C)		0.91
Water solubility	0.1 – 1 g/L	3.24 g/L
Solubility in organic solvents (n-octanol)	> 1 g/L	> 1 g/L
Solubility in organic solvents (DMSO)	> 1 g/L	> 1 g/L
Environmental fate and pathways
Biodegradation	OECD Guideline 302 B: > 97 % after 20 days	OECD Guideline 301 F: Readily biodegradable after 28 days
Ecotoxicological Information
Acute toxicity fish	LC50:     331.7 mg/L LC0:      220.0 mg/L LC100:   500.0 mg/L	LC50:     332 mg/L LC0:      220 mg/L LC100:   500 mg/L
Toxicological Information
Acute Toxicity, oral, rat	LD50: 1755 mg/kg bw	LD50: 1535 mg/kg bw
Acute Toxicity, oral, cat	Read across prediction: MetHb formation	MetHb formation
Skin irritation	Not irritating	Not irritating
Eye irritation	Not irritating	Not irritating
Skin sensitization (LLNA)	Read across prediction: Not sensitising	Not sensitising
Genetic toxicity in vitro (AMES)	negative	negative

Justification for selection of acute toxicity – oral endpoint
Most reliable study available

Justification for classification or non-classification

The LD50 value of 1755 mg/kg bw meets criteria for classification as acutely toxic Cat 4 according to REGULATION (EC) No 1272/2008.

Since formation of methemoglobin in humans is assumed and systemic availability for all three exposure routs is not unlikely a classification as Cat 4, H302/H312/332 irrespective of the routes tested is warranted.