3-anilino-5-methyl-5-(4-phenoxyphenyl)-1,3-oxazolidine-2,4-dione;famoxadone (ISO)

Neurotoxicity

Description of key information

Acute Neurotox Study: Systemic NOAEL (rat): 1000 mg.kg (male); 2000 mg/kg (females), No neurotox effects, OPP 81-8, Reliability = 1

Subchronic Neurotox Study: Systemic NOAEL: 200 ppm (males/females), no neurotox effects, OPP 82-7, Reliability = 1

Key value for chemical safety assessment

Effect on neurotoxicity: via oral route

Link to relevant study records

Reference

Reference 1

Endpoint:

neurotoxicity: acute oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPP 81-8 (Neurotoxicity Screening Battery)

Deviations:

no

GLP compliance:

yes

Limit test:

no

Specific details on test material used for the study:

Substance name: DPX-JE874
Lot #: JE874-221
Purity: 97.4%

Species:

rat

Strain:

other: Crl:CD®BR

Sex:

male/female

Route of administration:

oral: gavage

Vehicle:

other: 0.5% Tween 80 and 99.5% bottled, deionized water

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

Single dose

Frequency of treatment:

Single dose

Dose / conc.:

500 mg/kg bw (total dose)

Dose / conc.:

1 000 mg/kg bw (total dose)

Dose / conc.:

2 000 mg/kg bw (total dose)

No. of animals per sex per dose:

12

Control animals:

yes, concurrent vehicle

Clinical signs:

effects observed, non-treatment-related

Description (incidence and severity):

There were no compound-related clinical observations at any concentration in either males or females.

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Although there were no statistically significant differences in absolute body weight, on Test Day 2, the mean body weight value for 2000 mg/kg males was lower than the control value. In addition, male rats administered 2000 mg/kg had significantly lower (65%) body weight gain over the interval of test days 1-2 compared to control values. However, mean body weight values and mean body weight gain values for 2000 mg/kg males over the remainder of the study (test day intervals 2-8 and 8-15) were comparable to control values. Although the lover body weight gain for 2000 mg/kg males was transient, it was accompanied by decreased food consumption and therefore, was considered to be compound-related adverse effect.

There were no compound-related effects on mean absolute body weight evident for females at any dosage concentration. Females administered 500, 1000, or 2000 mg/kg had lower body weight gain (values were not statistically significant) compared to control values; however, there was no dose-response relationship evident. Therefore, the differences from control values for the 500, 1000, and 2000 mg/kg females were not considered to be compound related.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

Male rats administered 2000 mg/kg had significantly lower (13%) mean food consumption over the interval of Test Days 1-2 compared to the control value. Over the remainder of the study, however, food consumption values for males were similar to control for all dosage concentrations. The lower food consumption correlates with the lower body weight gain over the same interval, and therefore, it was considered to be a compound-related adverse effect.
There were no compound-related adverse effects on food consumption in females for any dosage concentration compared to control values. During the interval of Test Days 8-15, 1000 mg/kg females had significantly higher food consumption compared to control. A dose-response relationship was not evident; however, and it was not associated with an adverse effect of the test substance, so the higher food consumption in 1000 mg/kg females was not considered to be compound related.

Behaviour (functional findings):

effects observed, non-treatment-related

Description (incidence and severity):

There were no statistically significant differences compound-related effects at any dosage concentration in males or females for either forelimb grip strength or for hindlimb grip strength and with respect to footsplay.

Males administered 2000 mg/kg had a significantly higher incidence of palpebral closure on test day 1 both in the home cage (10/12) and in an open field (6/12) compared to controls (the incidences of palpebral closure in 0 mg/kg males were 5/12 and 1/12 in the home cage and in an open field, respectively). The incidences of the remaining 31 behavioral indices in the FOB battery, were similar to control for 500, 1000 or 2000 mg/kg males on test days 1, 8, and 15. During the baseline assessment, 2000 mg/kg males had a significantly higher incidence of urination during the assessment in the open field. This occurred prior to administration of the test substance, however, and was considered to be a spurious event. Since there were no converging neurotoxic effects on any other neurobehavioral parameters, the transient increase in incidence of palpebral closure may be related to a general feeling of malaise rather than neurotoxicity. The higher incidence of palpebral closure in 2000 mg/kg males on Test Day 1 is therefore considered to be an adverse effect only insofar it reflects on general malaise that is also manifested as reduced body weight gain.

There were no compound-related adverse effects on any FOB parameter measured either in the home cage or in a free roaming space for females at any dosage concentration. During the Test Day 1 evaluation, the incidence of urination for 1000 and 2000 mg/kg females while they were in the activity monitors was significantly higher compared to control (3/12 and 4/12 at 1000 and 2000 mg/kg, respectively, compared to 0/12 at 0 mg/kg). However, there is considerable variation in the incidence of urination, which ranged from 0/12 to 7/12 for controls, while the animals were in the activity monitors during the 4 evaluations. Therefore, the significantly higher incidence of urination was considered to be a spurious statistical event.

There were no compound-related adverse effects on motor activity in males at any dosage concentration. On the Test Day 15 evaluation, 1000 mg/kg males had a significantly lower number of movements in the 5th 10-minute block, and a lower (although not statistically significant) total number of movements over the 60-minute period. A dose-response relationship, however, was not evident, and the lower number of movements for the 1000 mg/kg males was not considered to be compound related. There were no statistically significant difference or compound-related effects on motor activity in females at any dosage concentration.

Neuropathological findings:

effects observed, non-treatment-related

Description (incidence and severity):

There were no compound-related gross or microscopic morphological changes detected in the central or peripheral nervous system of males or females at any dosage concentration.

Key result

Dose descriptor:

NOAEL

Effect level:

2 000 mg/kg bw (total dose)

Based on:

test mat.

Sex:

female

Remarks on result:

other: highest dose tested

Key result

Dose descriptor:

NOAEL

Effect level:

1 000 mg/kg bw (total dose)

Based on:

test mat.

Sex:

male

Basis for effect level:

body weight and weight gain

food consumption and compound intake

Conclusions:

NOAEL (rat): 1000 mg/kg (male); 2000 mg/kg (female, highest dose tested)

Executive summary:

Young adult male and female Crl:CD®BR rats (12 rats/gender/concentration) were administered a single dose of the test substance at concentration levels of 0, 500, 1000, or 2000 mg/kg by gavage. The study was conducted following US EPA guideline 81-8

A neurobehavioral test battery, consisting of motor activity (MA) and functional observational battery (FOB) assessments, was conducted on all rats prior to compound administration in order to obtain baseline measurements. This neurobehavioral test battery was conducted again following dosing on test day 1 (approximately 1-3 hours after compound administration), and on test days 8 and 15. Body weights were recorded on the day of baseline FOB and MA assessments, before exposure on test day 1, and on test days 2, 8, and 15. Food consumption was recorded for the intervals between test days 1-2, 2-8, and 8-15. Clinical signs were recorded before dosing on test day 1 and daily thereafter through test day 14 except on neurobehavioral test days.

After completion of the final neurobehavioral test, six rats per group were anesthetized by pentobarbital anesthesia followed by whole-body in situ perfusion. Tissue samples from the nervous system and muscle were saved from all groups. Only tissues from the control (0 mg/kg) and high dose groups (2000 mg/kg) were processed for histopathology and examined.

A single oral dose of test substance at a concentration of 2000 mg/kg caused minimal compound-related effects in adult male rats. Males administered 2000 mg/kg had significantly lower body weight gain and significantly lover food consumption over the interval of Test Days 1-2. Over the remainder of the test period, however, there were no compound-related effects on body weight gain and food consumption values. There were no adverse compound-related effects on survival, clinical signs of toxicity, indicators of neurotoxicity or morphological changes in the nervous system at any dosage concentration. Males administered 2000 mg/kg also had a significantly increased incidence of palpebral closure on test day 1. An increase in the incidence of palpebral closure along with the decreased body weight gain and decreased food consumption for 2000 mg/kg males was interpreted as general malaise. In contrast to the males, there were no compound-related effects in females for body weight or food consumption at any dosage concentration. In addition, compound-related effects on survival, clinical signs of toxicity, indicators of neurotoxicity, and nervous system morphology were not affected by administration of test substance to female rats at any dosage concentration.

Under the conditions of the study, the no-observed-adverse-effect level (N0AEL) in male rats is considered to be 1000 mg/kg based on the lower body weight gain and food consumption and a higher incidence of palpebral closure at 2000 mg/kg. The NOAEL in females is considered to be the highest dose tested, 2000 mg/kg.

Reference 2

Endpoint:

neurotoxicity: sub-chronic oral

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: U.S. EPA Pesticide Guidelines, Subdivision F, 82-7

Deviations:

no

GLP compliance:

yes

Limit test:

no

Specific details on test material used for the study:

Substance name: DPX-JE874
Lot #: JE874-221
Purity: 97.4%

Species:

rat

Strain:

other: Crl:CD®BR

Sex:

male/female

Route of administration:

oral: feed

Vehicle:

other: diet

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

90 days

Frequency of treatment:

Continuously in diet

Dose / conc.:

50 ppm

Dose / conc.:

200 ppm

Dose / conc.:

800 ppm

No. of animals per sex per dose:

12

Control animals:

yes, plain diet

Clinical signs:

effects observed, non-treatment-related

Description (incidence and severity):

There were no compound-related clinical observations at any dietary concentration in either males or females.

Mortality:

no mortality observed

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Mean body weight of 800 ppm males was significantly lower than the control value on test day 21; and body weights were generally lower, although not statistically significant, than the control values over the 90-day period. Mean body weight gain for 800 ppm males was also significantly lower for test days 0-7 compared to the control value. Cumulative mean body weight gain for test days 0 to 21 was 15% lower for 800 ppm males compared to control males. However, the 800 ppm males appeared to recover such that the cumulative mean body weight gain for test days 0-49 was only 8% lower than the control value; and for test days 0-91, cumulative mean body weight gain was 6% lower than the control value. The lover body weights and body weight gain values for 800 ppm males were reflected by the lower food consumption and food efficiency values during test days 0-21. Although the cumulative body weight gain for 800 ppm males was only 6% lower than the control values over the interval of test days 0-91 in the current study, the differences in body weight and weight gain were accompanied by lower food efficiency. Therefore, the body weight and weight gain differences in 800 ppm males were considered to be compound-related. Although the animals appeared to compensate for the effects which occurred during the first 3 weeks of the study, the effects on body weight and weight gain were considered to be adverse. There were no compound-related effects on body weight or weight gain in male rats at 50 or 200 ppm.

Mean body weight of female rats fed diets containing 800 ppm of the test substance was significantly lower on test days 42-56 and 70-84 compared to control values. Mean body weight gain of 800 ppm females was significantly lower for test days 0-7; and cumulative body weight gain values were significantly lower for the test day intervals of 0-49 (21% lower) and 0-91 (20% lower) compared to control values. The lower body weights and body weight gain values for the 800 ppm females is also reflected by significantly lower food consumption during test days 0-7, and significantly lower food efficiency over the intervals of test days 0-49 and 0-91. Since cumulative body weight gain of 800 ppm females was 20% lower than the control values over the 90-day feeding period, and was accompanied by significantly lower food efficiency, the lower mean body weights and cumulative body weight gain were considered to be compound related and adverse. There were no compound related effects on body weight or weight gain in female rats at 50 or 200 ppm.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

During the first week of the study (test days 0-7) food consumption of 800 ppm males and females was significantly lower than their respective controls. The lower food consumption in 800 ppm males was considered to be compound related and adverse since it was accompanied by lower body weight and weight gain. The effects on food consumption in 800 ppm females was considered to be compound related and adverse since the body weight decrement persisted throughout the course of the study.

There was no compound-related effects on food consumption in either males or females at dietary concentrations of 50 or 200 ppm. For the interval of test days 63-70, 200 ppm males had significantly lower food consumption compared to the control value. However, this difference was considered to be due to biological variation since a dose-response relationship was not evident.

The mean daily intake of test substance over the course of the 90-day feeding period for male rats was 0, 2.9, 11.7, and 46.9 mg/kg body weight and for female rats was 0, 3.7, 14.4, and 59.3 mg/kg body weight for 0, 50, 200, and 800 ppm, respectively.

Food efficiency:

effects observed, treatment-related

Description (incidence and severity):

Food efficiency was lower for 800 ppm males during test days 0-21 (statistically significant only for the interval of test days 14-21). Similarly, food efficiency was significantly lower for 800 ppm females over the intervals of test days 0-49 and 0-91. The lower food efficiency in 800 ppm males was considered to be compound related and adverse since it was accompanied by lower body weight and weight gain. The effects on food efficiency in 800 ppm females was considered to be compound related and adverse since the body weight decrement persisted throughout the course of the study.
There was no compound-related effects on food efficiency in either males or females at dietary concentrations of 50 or 200 ppm.

Behaviour (functional findings):

effects observed, non-treatment-related

Description (incidence and severity):

There were no statistically significant differences or compound-related effects at any dietary concentration in males of females for either forelimb grip strength or for hindlimb grip strength.

There were no compound-related effects at any dietary concentration in males or females on foot splay. At the week 4 evaluation, 50 ppm females had a significantly higher mean foot splay value compared to the control value. However, since a dose-related trend was not evident, it was considered to be due to biological variation.

There were no compound-related adverse effects among the 33 behavioral indices in the FOB battery at the week 4, 8, or 13 evaluations for either males or females at any dietary concentration. During the week 4 evaluation, the incidence of low arousal for 800 ppm males was significantly higher compared to control (2/12, 0/12, 0/12, and 4/12 for 0, 50, 200, and 800 ppm males, respectively). During the week 13 evaluation, however, 800 ppm males had a significantly higher incidence of high arousal compared to control (0/12, 0/12, 0/12, 2/12 for 0, 50, 200, and 800 ppm males, respectively). Since these incidences for the 800 ppm males were not consistent with time, they were considered to be spurious. Furthermore, there was no evidence of central nervous system sedation or excitation in the motor activity assessment.

There were no compound-related adverse effects on motor activity in males or females at any dietary concentration.
For males, there were no statistically significant differences in either duration of movement or number of movements at any evaluation. Females fed diet containing 200 ppm test substance had significantly higher duration of movement during the second, third, and sixth 10-minute blocks, and significantly higher total duration of movement at the week 4 evaluation. These differences were also reflected by a significantly higher number of movements in the sixth 10-minute block and in the total number of movements during the week 4 evaluation for 200 ppm females. Since these differences did not persist over the duration of the study, and since a dose-response relationship was not evident, they considered to be spurious.

Neuropathological findings:

effects observed, non-treatment-related

Description (incidence and severity):

There were no compound-related gross or microscopic morphological changes detected in the central or peripheral nervous system of males or females in the 800 ppm concentration groups. Since compound-related changes were not detected at 800 ppm, microscopic evaluation of tissues from the 50 and 200 ppm concentration groups was not conducted.

Key result

Dose descriptor:

NOAEL

Effect level:

200 ppm

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

food consumption and compound intake

food efficiency

Conclusions:

NOAEL (rat): 200 ppm (male/female)

Executive summary:

The purpose of this study vas to assess the potential neurotoxicity of subchronic exposure of adult rats to test substance. Young adult male and female Crl:CD®BR rats (12 rats/gender/concentration) were administered diets containing 0, 50, 200, or 800 ppm of test substance for approximately 90 days. Samples of the prepared diet were collected periodically during the study to verify the concentration of test substance. The rats were weighed weekly throughout the study, and on the days of neurobehavioral testing. Food consumption was determined weekly and clinical signs of toxicity were monitored throughout the study.

A neurobehavioral test battery, consisting of motor activity and functional observational battery assessments, was conducted on all study rats prior to compound administration in order to obtain baseline measurements. This neurobehavioral test battery was conducted again following approximately 4, 8, and 13 weeks of dietary administration. After completion of the final neurobehavioral test on week 13, six rats per gender per concentration were anesthetized by pentobarbital anesthesia followed by whole-body in situ perfusion. Tissue samples from the nervous system and muscle were saved from all groups. Only tissues from the control (0 ppm) and high concentration groups (800 ppm) were processed for histopathology and examined.

Dietary administration of the test substance to adult male and female rats at concentrations up to 800 ppm caused minimal compound-related effects. Males and females administered 800 ppm diet had a compound-related decrease in body weight, body weight gain, food consumption, and food efficiency. Since the decrement in body weight gain for females exceeded 10% of the control value by the end of the 90-day feeding period, these effects were considered to be adverse.

There were no other compound-related effects detected in clinical observations, neurobehavioral evaluations, motor activity, or nervous system morphology in either males or females at any dietary concentration. Therefore, evidence of neurotoxicity was not observed at dietary concentrations which elicited compound-related changes in body weight and food consumption parameters, in clinical pathology parameters, and in morphological structure and function.

Under the conditions of this study, the no-observed-adverse-effect level was considered to be 200 ppm for males and females based on the decrements in body weight, body weight gain, food consumption, and food efficiency at 800 ppm.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Quality of whole database:

Guideline studies were available in rats for acute and 90-day exposures.

Justification for classification or non-classification

No neurotoxic effects were observed in acute or 90-day neurotoxicity studies.  Therefore, the test substance is not classified for neurotoxicity according to EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.