2,2,6,6-tetramethyl-4-oxopiperidinooxy

Repeated dose toxicity: oral

Administrative data

Endpoint:

short-term repeated dose toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1996-12-23 to 1997-5-23

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: A well conducted study according to guidelines and in complance with GLP

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1997

Report date:

1997

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

EU Method B.7 (Repeated Dose (28 Days) Toxicity (Oral))

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: The Japanese Ministry of Health and Welfare (MHW) Guidelines 1986 for a 28-day repeat dose oral toxicity study as required by Japanese Chemicals Substances Control Law 1973 of the Ministry of International Trade and Industry (MITI) amended 1986.

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

2,2,6,6-tetramethyl-4-oxopiperidinooxy

EC Number:

220-778-7

EC Name:

2,2,6,6-tetramethyl-4-oxopiperidinooxy

Cas Number:

2896-70-0

Molecular formula:

C9H16NO2

IUPAC Name:

(2,2,6,6-tetramethyl-4-oxopiperidin-1-yl)oxidanyl

Details on test material:

- Physical state: Solid
- Analytical purity: 89.3%

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River UK Limited, Manston, Kent, UK
- Age at study initiation: 5-6 weeks
- Weight at study initiation:Males : 121-159g; Females : 118-150g
- Housing: 5/cage
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: 8 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C):21 ± 2°C
- Humidity (%): 55 ± 15%
- Air changes (per hr): >15
- Photoperiod (hrs dark / hrs light): 12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

polyethylene glycol

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

28 Days

Frequency of treatment:

Daily

Doses / concentrations

Remarks:

Doses / Concentrations:
15, 150, 1,000 mg/kg
Basis:
actual ingested

No. of animals per sex per dose:

5

Control animals:

yes, concurrent vehicle

Details on study design:

In addition to the treatment groups of 5 male/5 female rats dosed with 15, 150, 1000 mg/kg and vehicle control, two satellite treatment groups were dosed with either 1000 mg/kg or vehicle control and observed for a post treatment period of 14 days.

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Before dosing, 1 and 5 hours after dosing during the working week. Before dosing and 1 hour after dosing at weekends.
During the treatment free period (recovery animals), observations were made twice daily (once daily at weekends).

BODY WEIGHT: Yes
- Time schedule for examinations: Day 0, 7, 14, 21, 28. The recovery animals were also examined on days 35 and 42.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study):
Water consumption for each cage group was monitored.

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: Five males and five females from each dose level at the end of treatment period (Day 28) and on all recovery group animals at the end of the treatment free period (Day 42)
- Anaesthetic used for blood collection: No
- Animals fasted: No
- How many animals: Five males and five females from each dose level and all recovery animals.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: The end of treatment period (Day 28) and at the end of the treatment free period (Day 42) for recovery animals.
- Animals fasted: No
- How many animals: Five males and five females from each dose level and all recovery animals.

URINALYSIS: Yes
- Time schedule for collection of urine: Week 4 and recovery animals during week 6.
- Metabolism cages used for collection of urine: Yes
- Animals fasted: Yes

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

Statistics:

Data showing a significant dose response were analysed using one way analysis of variance (ANOVA) incorporating Levene's test for homogeneity of variance. Where Levene's test showed unequal variances the data were analysed using nonparametric methods: Kruskal-Wallis ANOVA and Mann-Whitney "U" test.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Water consumption and compound intake (if drinking water study):

no effects observed

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

1,000 mg/kg/day - females - significant decrease in red blood cell parameters (haemoglobin, haematocrit, erythrocyte count, mean corpuscular haemoglobin concentration). There were no effects in the 14 day recovery group.

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

1,000 mg/kg/day -males - increased liver weight (abs/rel); females - significant increase in liver weight (rel), increased adrenal weight (abs/rel), increased spleen weight (rel). There were no effects in the 14 day recovery group.

Gross pathological findings:

effects observed, treatment-related

Description (incidence and severity):

1000 mg/kg/day - male (1/5) - pale liver; female (1/5) - enlarged adrenal gland. There were no effects in the 14 day recovery group.

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

1,000 mg/kg/day - males (3/5) - centrilobular hepatocyte enlargement. There were no effects in the 14 day recovery group.

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY
No clinical signs of toxicity were observed in the animals throughout the test period. Increased salivation was observed in animals in the 1000mg/kg/day dose group around the time of dosing accompanied by red/brown staining of the external body surfaces. This can be associated with an unpleasant tasting or irritating test material and is not thought to be related to toxicity. One animal from the 150 mg/kg/day dose group showed clinical abnormalities and was not considered to be related to toxicity.

BODY WEIGHT AND WEIGHT GAIN
No adverse effects on body weight development were detected.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study)
There was no adverse effect on food consumption detected during the study.

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study)
Daily visual inspection of the water bottles revealed no differences between treatment groups and control groups.

HAEMATOLOGY
Females treated with 1000mg/kg/day showed significant reductions in haemoglobin, haematocrit, erythrocyte count and mean corpuscular haemoglobin concentration with one or two animals showing values outside normal ranges for each parameter.
No changes were observed for recovery females after the 14 day observed period or males dosed with 1000mg/kg/day. No changes were observed for animals or either sex dosed with 15 or 150 mg/kg/day.

CLINICAL CHEMISTRY
Several parameters showed a statistically significant difference between treated animals and controls; however the dose-response relationships were inconclusive. In the absence of any associated changes in other parameters which may indicate target organ toxicity, these intergroup differences were not considered to be toxicologically significant.

URINALYSIS
There were no treatment related effects in the parameters measured that could be attributable to test material toxicity. An increase in the urine volume, of reduced specific gravity, was observed in animals of both sexes in the 1000mg/kg/day and females in the 150 mg/kg/day treatment group. As no evidence of an effect on kidney function was observed, the increase was considered to be related to increased salivation and possible elevated water consumption although this was not detected by visual inspection of the water bottles.

ORGAN WEIGHTS
Males treated with 1000 mg/kg/day showed statistically significant increases in liver weight, both absolute and relative to bodyweight when compared to controls. Females treated with 1000mg/kg/day showed a significant increase in liver weight (relative to bodyweight) and also absolute and relative adrenal weight and group mean relative spleen weight.
With the exception of elevated relative liver weights amongst recovery females 1000mg/kg/day a complete regression of organ weight changes was observed after the 14 day post treatment period.

No treatment-related organ weight changes were detected in the 150 or 15 mg/kg/day treatment groups. Remaining statistically significant differences were either confined to recovery group animals or isolated instances and were not considered to be toxicologically significant.

GROSS PATHOLOGY
In the 1000mg/kg/day treatment group, one male showed small pale areas on the left lobe of the liver, whilst one female showed enlarged adrenals at sacrifice.
No treatment related macroscopic abnormalities were detected for recovery group animals or animals dosed with 150 or 15 mg/kg/day.
Hydronephorsis was recorded for one recovery control female and one male from the 150 mg/kg/day dose group and was not considered dose related and not toxicologically significant.

HISTOPATHOLOGY: NON-NEOPLASTIC
Treatment related changes were observed in the liver. Centrilobular hepatocyte enlargement was observed for three male rats in the 1000mg/kg/day dose group. Male rats from remaining treatment groups were not affected. Such a change is commonly observed in the rodent liver following the administration of xenobiotics. In the recovery animals, regression of the condition was observed after fourteen days without treatment.
No other evidence of treatment related morphological changes were observed.

Effect levels

Dose descriptor:

NOEL

Effect level:

150 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

haematology

histopathology: non-neoplastic

organ weights and organ / body weight ratios

Target system / organ toxicity

Critical effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

The NOEL in a 28 day oral gavage study in rats with 2,2,6,6-tetramethyl-4-oxopiperidinooxy was 150 mg/kg/day. The effects in the high dose
group of 1,000 mg/kg/day were a decrease in red blood cell parameters, increased organ weights and gross and microscopic changes in the liver.

Executive summary:

A 28-day repeated dose study was performed in accordance with EU Method B7 and GLP, to assess the systemic toxicity of 2,2,6,6-tetramethyl-4-oxopiperidinooxy to Sprague-Dawley rats.

The test material was administered by gavage to three groups, each containing five male and five female Sprague-Dawley rats for 28 consecutive days. The treatments were administered at doses of 15, 150 and 1000mg/kg/day. A control group was dosed with vehicle (Polyethylene glycol 400). Two recovery groups of five male and five female animals were treated with 1000mg/kg/day or the vehicle alone for 28 consecutive days and then maintained without treatment for a further 14 days.

 

Clinical signs, bodyweight development, food and water consumption were monitored during the study. Haematology, blood chemistry and urinalysis were evaluated for all non-recovery animals at the end of the 28-day treatment period and all recovery group animals at the end of the 14-day treatment free period.

 

All animals were subject to a gross necropsy examination and histopathological evaluation of selected tissues was performed.

 

There were no mortalities during the study. No significant effects were observed in the body weights, food consumption or water consumption. Animals treated with the test material showed no adverse clinical signs that could be attributed to toxicity of the test material.

 

Females in the 1000mg/kg/day treatment group showed statistically significant reductions in haemoglobin, haematocrit, erythrocyte count and mean corpuscular haemoglobin concentrations when compared to the controls. No such changes were detected for males treated with 1000mg/kg/day, or animals treated with 150 or 15 mg/kg/day.

Recovery group animals showed no haematological changes after 14 days without treatment.

 

Neither the blood chemistry nor the urinalysis results showed any treatment related effects.

 

The liver weights of males treated with 1000mg/kg/day was increased both absolute and in comparison with the controls. Females from the 1000mg/kg/day showed an increase in the relative and absolute adrenal weights in addition to an increase in relative spleen weight.

No treatment related organ weight changes were detected in the 150 or 15 mg/kg/day dose groups after 28 days or in the recovery animals at the end of the 14-day treatment free period.

 

In the 1000mg/kg/day treatment group, one male showed small pale areas on the left lobe of the liver, whilst one female showed enlarged adrenals at sacrifice.

No treatment related macroscopic abnormalities were detected for recovery group animals or animals dosed with 150 or 15 mg/kg/day. 

 

Centrilobular hepatocyte enlargement was observed for three male rats in the 1000mg/kg/day dose group. In the recovery animals, regression of the condition was observed after14 days without treatment.

No other evidence of treatment related morphological changes were observed in the remaining treatment groups.

 

The test substance, 2,2,6,6-tetrametyl-4-oxopipeidinooxy, resulted in toxicologically significant adverse effects when administered orally at a dose level of 1000mg/kg/day for 28 consecutive days.

No effects were observed in the 15 or 150 mg/kg/day treatment groups therefore the ’No Observed Effect Level’ (NOEL) was considered to be 150 mg/kg/day.