Octadecanoic acid, 1-(2-hydroxy-2-methylpropoxy)-2,2,6,6-tetramethyl-4-piperidinyl ester

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:

2001

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2001

Report date:

2001

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity Study in Rodents)

Version / remarks:

July 27 1995

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: Japanese Substance Law 1987 (December 9, 1986) by Environmental Agency (no. 700), MHW (10-93) and MITI (1014)

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Details on test material:

- Expiration date of the lot/batch: None provided
- Receipt date: February 7, 2000
- Appearance: White to offwhite granules
- storage: stored at room temperature.

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on species / strain selection:

The laboratory rat was selected as the animal model for this study since it is one of the species recommended by the regulatory agencies for oral toxicity testing. Oral administration of the test article was selected since it is a potential route of human exposure.

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Inc., Raleigh, North Carolina
- Age at study initiation: 8,5 weeks
- Weight at study initiation: 240 to 272 grams for males and 184 to 197 grams for females.
- Housing: suspended stainless steel cages
- Diet (e.g. ad libitum): PMI Certified Rodent Chow, free access
- Water (e.g. ad libitum): tap water ad libitum
- Acclimation period: 14d

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18-26
- Humidity (%): 30-70
- Air changes (per hr): 10-15
- Photoperiod (hrs dark / hrs light): 12

IN-LIFE DATES: 23.8.-18.10.2000

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

polyethylene glycol

Details on oral exposure:

DIET PREPARATION
- Rate of preparation of diet (frequency): weekly, continuously stirring
- Mixing appropriate amounts with (Type of food): The mixtures were dispensed into amber glass jars daily for dosing.
- Storage temperature of food: RT

VEHICLE PEG 400 and Tween 80 mix
- Justification for use and choice of vehicle (if other than water): not water soluble
- Lot/batch no. (if required): 992286

Analytical verification of doses or concentrations:

no

Details on analytical verification of doses or concentrations:

Prior to initiation of the 28-day study, homogeneity and stability analyses were performed on concentrations of the test article in the vehicle which bracketed the low- and high-doses administered in this study. Homogeneity analyses were performed on triplicate samples taken from the top, middle and bottom of the two mixtures. Stability of the test article In the vehicle was evaluated on triplicate samples at 0, 5 and 8 days following preparation. Concentration verification analysis was performed on the vehicle and each test article dosing mixture during weeks 1, 2, 3 and 4. The homogeneity, stability and concentration verification analyses were conducted at SLI.

Duration of treatment / exposure:

28d

Frequency of treatment:

daily

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

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

Doses / concentrations 2

Dose / conc.:

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

Doses / concentrations 3

Dose / conc.:

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

Doses / concentrations 4

Dose / conc.:

1 000 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

5

Control animals:

yes, concurrent vehicle

Details on study design:

Clinical Observations
General health/mortality and moribundity checks were performed twice daily, in the morning and afternoon. A cage-side clinical observation was
performed for each animal daily, between one-half hour and two hours following dosing, and daily during the recovery phase.

Functional Observation Battery (FOB)
a. Home Cage Observations
b. Removal from Home Cage Observations
c. Open Field Observations
d. Manipulative Tests
e. Motor Activity

Bodyweights
Individual bodyweights were recorded on days -2, 8, 15, 22 and 28 (during the treatment phase) and days 35 and 41 (during the recovery phase). In addition, a terminal body weight was recorded on the day of scheduled euthanasia (day 29 or 42) for calculation of relative organ weight data.

Food Consumption
Food consumption was recorded on days -2, 8, 15, 22 and 28 (during the treatment phase) and days 35 and 41 (during the recovery phase).

Blood was collected from all animals on the day of scheduled euthanasia at the end of the treatment phase (day 29) or the recovery phase (day 42) for evaluation of selected hematology, coagulation and biochemistry parameters. The blood samples obtained for hematology and biochemistry evaluations were collected via the orbital plexus while the animals were under light isoflurane anesthesia. The blood samples obtained for the coagulation evaluations were collected via the vena cava at necropsy. Feed was withheld overnight prior to blood collection, however, water was available.

Urinalysis
Urine samples were collected from all animals overnight prior to scheduled euthanasia at the end of the treatment phase (day 29) or the recovery phase (day 42). Each rat was housed in a urine collection cage without food, however, the animals were allowed access to water.

Ophthalmology
Ophthalmologlcal examinations were performed on all rats by a board-certified veterinary ophthalmologist. Dr. David A. Wilkie, near the end of the treatment phase (day 23) and the recovery phase (day 40). Eyes were dilated using 0.5% Mydriacyl®ophthalmicsolution priorto biomicroscopic and indirect ophthalmoscopic examination.

Gross Necropsy
All animals were subjected to a complete gross necropsy at the time of death or scheduled euthanasia (day 29 or 42). The necropsy examination included evaluation of the external surfaces of the body and all viscera. At the end of the treatment phase, five males and five females per group were euthanized on day 29. At the end of the recovery phase, the remaining five males and five females in the control and high-dose groups were euthanized on day 42.

Histopathology
All tissues and organs collected at necropsy (days 29 and 42) from all animals in the control and high-dose groups were processed for histopathological examination. The tissues were trimmed, embedded in paraffin, sectioned and stained with hematoxylin and eosin.

Positive control:

no positive controls

Examinations

Observations and examinations performed and frequency:

Clinical observations
General health/mortality and moribundity checks were performed twice daily, in the morning and afternoon. A cage-side clinical observation was
performed for each animal daily, between one-half hour and two hours following dosing, and daily during the recovery phase.

Functional Obseervation Battery (FOB)
An abbreviated functional observation battery (home cage, removal from home cage and open field) was performed once priorto initiation of dosing
and once during weeks 1, 2 and 3 (days - 1 , 5, 12 and 19, respectively) for each animal. A full FOB assessment (home cage, removal from home cage, open field, manipulative tests and motor activity) was performed during weeks 4 and 6 (days 26/27/28 and 40, respectively). All FOB assessments (except the pretest) were performed blind (animals were not identified by group).

Body weights
Individual bodyweights were recorded on days -2, 8, 15, 22 and 28 (during the treatment phase) and days 35 and 41 (during the recovery phase). In
addition, a terminal body weight was recorded on the day of scheduled euthanasia (day 29 or 42) for calculation of relative organ weight data.

Food consumption
Food consumption was recorded on days -2, 8, 15, 22 and 28 (during the treatment phase) and days 35 and 41 (during the recovery phase).

Ophthalmology
Ophthalmologlcal examinations were performed on all rats by a board-certified veterinary ophthalmologist. Dr. David A. Wilkie, near the end of the treatment phase (day 23) and the recovery phase (day 40). Eyes were dilated using 0.5% Mydriacyl®ophthalmicsolution priorto biomicroscopic and
indirect ophthalmoscopic examination.

Sacrifice and pathology:

Clinical Pathology
Blood was collected from all animals on the day of scheduled euthanasia at the end of the treatment phase (day 29) or the recovery phase (day 42) for evaluation of selected hematology, coagulation and biochemistry parameters. The blood samples obtained for hematology and biochemistry
evaluations were collected via the orbital plexus while the animals were under light isoflurane anesthesia. The blood samples obtained for the
coagulation evaluations were collected via the vena cava at necropsy. Feed was withheld overnight prior to blood collection, however, water was
available.

Gross necropsy
All animals were subjected to a complete gross necropsy at the time of death or scheduled euthanasia (day 29 or 42). The necropsy examination included evaluation of the external surfaces of the body and all viscera. At the end of the treatment phase, five males and five females per group were euthanized on day 29. At the end of the recovery phase, the remaining five males and five females in the control and high-dose groups were euthanized on day 42. The animals were euthanized by carbon dioxide inhalation followed by exsanguination. The animals were fasted overnight prior to euthanasia. A board-certified veterinary pathologist was present at the scheduled necropsy at the end of treatment phase and at the end of the recovery phase (Dr. William H. Baker and Dr. J. Dale Thurman, respectively).

Histopathology
All tissues and organs collected at necropsy (days 29 and 42) from all animals in the control and high-dose groups were processed for histopathological examination. The tissues were trimmed, embedded in paraffin, sectioned and stained with hematoxylin and eosin. Histology was
performed by HistoTechniques, Powell, Ohio, and the tissues were examined microscopically by a board-certified veterinary pathologist.

Statistics:

All statistical analyses were performed using a Digital MicroVax 3100 computer. Parametric data was analyzed by one-way analysis of variance (ANOVA). When significance was observed with ANOVA, group by group comparisons were performed using the Tukey-Kramer method. All tests were two-tailed with a minimum significance level of 5%. Rank and count data were analyzed by Kruskal-Wallis Nonparametric ANOVA. When significance was observed, group by group comparisons were performed using Kruskal-Wallis Nonparametric ANOVA. Descriptive (categorical) and quantal data were analyzed by Fischer's Exact Test. When significance was observed, group by group comparisons were performed using Fischer's Exact Test.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Description (incidence and severity):

No other notable clinical abnormalities except for the one dead animal were noted during this study.

Mortality:

no mortality observed

Description (incidence):

No treatment-related mortalities were noted during this study. One control male was found dead on study day 23. The most notable clinical signs that preceded this mortality initially occurred on study day 22 and included diarrhea, salivation, urine stained haircoat and dark material around the nose. Gross necropsy of this animal revealed a distended and thickened bladder/urethra with a calculi in the bladder. Therefore, this mortality was considered a secondary effect of the bladder calculi which resulted in renal failure. This death was not considered treatment related since this was a control animal and bladder calculi are not uncommon in this species/sex of rat.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

Mean body weight gains for males in group 2 were statistically lower than controls on days 8-15. There were no other statistically or biologically significant body weight effects noted among the groups during the treatment or recovery phases.

Food consumption and compound intake (if feeding study):

no effects observed

Description (incidence and severity):

There were no statistically or toxicologically significant differences in mean food consumption (grams/animal/day) among the groups during the treatment or recovery phases.

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

no effects observed

Description (incidence and severity):

No test article-related ocular abnormalities were noted in any of the study animals near the end of the treatment or recovery phases.

Haematological findings:

no effects observed

Description (incidence and severity):

There were no statistically or toxicologically significant differences in hematology and coagulation data among the groups during the treatment or
recovery phases.

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

There were no toxicologically significant differences In biochemistry data among the groups during the treatment or recovery phases. A slight, but statistically significant increase in chloride was observed in the 1000 mg/kg/day males on day 42. In addition, a statistically significant
decrease in triglycerides was observed in the 1000 mg/kg/day females on day 42. These findings were not considered to be biologically meaningful since they occurred at the end of the recovery phase but not during the treatment phase and were generally within the SLI historical control range for these parameters.

Urinalysis findings:

no effects observed

Description (incidence and severity):

There were no statistically significant or biologically meaningful differences among the groups in the urinalysis parameters evaluated at the end of the treatment or recovery phases.

Behaviour (functional findings):

no effects observed

Description (incidence and severity):

There was no evidence of neurological abnormalities in males or females in the test article treated groups. The parameters examined during the weekly functional observation battery did not reveal any notable differences between the treated and control animals nor when the pretest (week -1) results were compared to the week 1-6 results. A slight, statistically significant increase in rearing was noted in the 1000 mg/kg/day males during study week 6. No statistically significant differences were observed in rearing during study weeks 1-4. This finding was not considered toxicologically meaningful since similar effects did not occur in any other parameter within any single neurological functional domain and this finding was noted at the end of the recovery phase.

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

No toxicologically significant organ weight effects were noted in any of the study animals near the end of the treatment or recovery phases. A statistically significant Increase in relative testes/epididymides weight was noted in the 100 mg/kg/day males on day 29. A statistically significant decrease in absolute thyroid/parathyroid weight and heart weight was noted in the 1000 mg/kg/day males on day 42. A statistically significant decrease In absolute ovarian weight was also noted in the 1000 mg/kg/day females on day 29. These differences were not considered toxicologically meaningful since the effects did not occur in a dose-related manner, occurred only in either the absolute or relative comparisons and there was no related pathology noted microscopically.

Gross pathological findings:

effects observed, non-treatment-related

Description (incidence and severity):

Gross necropsy of the one control male that died on study day 23 revealed a distended and thickened bladder/urethra with a calculi in the bladder. Therefore, this mortality was considered a secondary effect of the bladder calculi which resulted in renal toxicity. This death was not considered treatment-related since this was a control animal and bladder calculi are not uncommon in this species/sex of rat. No remarkable gross necropsy observations were noted for the surviving males or females at the end of the treatment or recovery phases.

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

In the control male that died on study day 23, histopathological examination confirmed the gross observations in the bladder and urethra and supported calculi induced renal failure as the most likely cause of death. In the animals that survived, all microscopic changes were considered spontaneous and unrelated to treatment or within the limits of normal variation.

Effect levels

Dose descriptor:

NOEL

Effect level:

1 000 mg/kg bw/day (actual dose received)

Sex:

male/female

Basis for effect level:

other: absence of treatment-related adverse effects

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Table 2: Summary of survival and clinical observations

		Male				Female
Group		1	2	3	4	1	2	3	4
Level [mg/kg bw/day]		0	100	500	1000	0	100	500	1000
Dead -         Found dead -         Scheduled euthanasia	Day 1 – 29	1/1 5/5	0/0 5/5	0/0 5/5	0/0 5/5	- 5/5	- 5/5	- 5/5	- 5/5
Excreta -         Diarrhea		1/1	0/0	0/0	0/0	-	-	-	-
Body -         Urine stain -         Fecal stain		1/1 1/1	0/0 0/0	0/0 0/0	0/0 0/0	-	-	-	-
Eyes -         Dark material around eye(s)		1/1	0/0	0/0	0/0	-	-	-	-
Nose / mouth -         Malalignment -         Dark material around nose -         Scab(s) -         Swelling -         Dark material around mouth		1/1 1/1 - - -	0/0 0/0 - - -	0/0 0/0 - - -	0/0 0/0 - - -	- 0/0 0/0 0/0 0/0	- 0/0 0/0 0/0 0/0	- 0/0 0/0 0/0 0/0	- 2/1 2/1 2/1 1/1
Post-dose -         Diarrhea -         Urine stain -         Salivation		2/1 1/1 1/1	0/0 0/0 0/0	0/0 0/0 0/0	0/0 0/0 0/0	-	-	-	-
Dead -         Scheduled euthanasia	Day 30 - 42	4/4	-	-	5/5	5/5	-	-	5/5
Nose / mouth -         Dark material around nose -         Scab(s)		-	-	-	-	0/0 0/0	-	-	2/1 5/1

Note: Data reflect the total occurrence of each clinical finding over the number of animals exhibiting the finding. Males and females in groups 2 and 3 were euthanized on day 29.

Table 3: Summary of body weight data (grams)

		Male				Female
Group		1	2	3	4	1	2	3	4
Level [mg/kg bw/day]		0	100	500	1000	0	100	500	1000
Day – 2	Mean SD N	261 6.8 10	267 4.4 5	265 5.5 5	262 9.4 10	192 4.2 10	191 4.8 5	192 4.7 5	192 4.2 10
Day 8	Mean SD N	309 8.2 10	312 9.5 5	322 11.0 5	312 12.3 10	211 7.5 10	211 7.5 5	215 3.1 5	212 6.7 10
Day 15	Mean SD N	340 10.9 10	333 18.1 5	354 12.5 5	340 16.7 10	223 8.2 10	220 12.6 5	226 7.3 5	223 6.5 10
Day 22	Mean SD N	361 16.4 10	357 22.1 5	383 15.0 5	363 18.4 10	232 8.7 10	227 13.3 5	233 4.5 5	229 8.0 10
Day 28	Mean SD N	373 20.6 9	361 31.9 5	389 17.6 5	374 20.3 10	230 9.0 10	228 12.8 5	234 4.7 5	229 8.0 10
Day 35	Mean SD N	408 12.9 4	-	-	401 21.0 5	235 9.8 5	-	-	242 2.3 5
Day 41	Mean SD N	426 17.5 4	-	-	412 20.2 5	238 12.3 5	-	-	244 6.8 5

Table 4: Summary of gross necropsy observations

		Male				Female
Group		1	2	3	4	1	2	3	4
Level [mg/kg bw/day]		0	100	500	1000	0	100	500	1000
Found dead	No. of animals examined	1	0	0	0	-	-	-	-
	Adrenal -         Reddened -         Enlarged	1 1	0 0	0 0	0 0	-	-	-	-
	Haircoat -         Wet matting -         Dark material -         Dried matted material	1 1 1	0 0 0	0 0 0	0 0 0	-	-	-	-
	Small intestine -         Content abnormal	1	0	0	0	-	-	-	-
	Large intestine -         Content abnormal	1	0	0	0	-	-	-	-
	Kidney -         Dilated pelvis -         Foci	1 1	0 0	0 0	0 0	-	-	-	-
	Lymph node -         Renal - enlarged	1	0	0	0	-	-	-	-
	Ureter -         Distended	1	0	0	0	-	-	-	-
	Urinary bladder / urethra -         Distended -         Thickened -         Calculi	1 1 1	0 0 0	0 0 0	0 0 0	-	-	-	-
Scheduled euthanasia Day 29	No. of animals examined	5	5	5	5	5	5	5	5
	All tissues within normal limits	3	2	2	1	2	3	4	2
	Ileum -         Content abnormal	-	-	-	-	0	0	0	1
	Cecum -         Content abnormal	0	0	1	1	-	-	-	-
	Colon -         Content abnormal	1	0	0	1	-	-	-	-
	Epididymides -         Green raised area	0	1	0	0	-	-	-	-
	Haircoat -         Dark material	0	0	1	0	0	1	0	0
	Liver -         Tan area(s)	0	2	0	0	0	1	1	1
	Lung -         Foci -         Dark red area(s)	0 0	0 1	0 2	3 2	0 2	0 0	0 0	1 2
	Stomach -         Raised area(s) -         Content abnormal	0 -	0 -	1 -	1 -	- 0	- 0	- 0	- 1
	Thymus -         Foci	1	1	0	0	-	-	-	-
	Ovary - Periovarian cyst	-	-	-	-	1	0	0	0
Scheduled euthanasia Day 42 Recovery phase	No. of animals examined	4	0	0	5	5	0	0	5
	All tissues within normal limits	2	-	-	3	2	-	-	2
	Diaphragm -         Thin area	-	-	-	-	0	-	-	1
	Liver -         Tan area(s)	1	-	-	0	1	-	-	0
	Lung -         Foci -         Dark read area(s)	1 0	-	-	0 2	- 3	-	-	- 1
	Thyroid gland -         Small	-	-	-	-	0	-	-	1

Table 5: Summary of absolute organ weight data (grams)

			Male				Female
Group			1	2	3	4	1	2	3	4
Level [mg/kg bw/day]			0	100	500	1000	0	100	500	1000
Scheduled euthanasia Day 29	Brain	Mean SD N	2.04 0.047 5	2.07 0.067 5	2.03 0.078 5	2.04 0.025 5	1.99 0.034 5	1.97 0.067 5	2.01 0.038 5	1.99 0.062 5
	Adrenals	Mean SD N	0.0558 0.01212 5	0.0512 0.01015 5	0.0574 0.01373 5	0.0545 0.00565 5	0.0658 0.00596 5	0.0623 0.00825 5	0.0610 0.01096 5	0.0641 0.00999 5
	Thyroids/ Parathyroid	Mean SD N	0.0168 0.00493 5	0.0187 0.00284 5	0.0185 0.0423 5	0.0167 0.00288 5	0.0151 0.00145 5	0.0128 0.00289 5	0.0142 0.00219 5	0.0129 0.00247 5
	Heart	Mean SD N	1.16 0.114 5	1.19 0.118 5	1.32 0.119 5	1.24 0.106 5	0.88 0.082 5	0.80 0.044 5	0.90 0.046 5	0.85 0.047 5
	Thymus	Mean SD N	0.37 0.033 5	0.35 0.134 5	0.46 0.136 5	0.45 0.055 5	0.45 0.130 5	0.37 0.078 5	0.53 0.119 5	0.44 0.083 5
	Spleen	Mean SD N	0.62 0.074 5	0.63 0.064 5	0.66 0.121 5	0.56 0.101 5	0.50 0.112 5	0.48 0.024 5	0.44 0.046 5	0.43 0.072 5
	Kidneys	Mean SD N	3.00 0.316 5	3.09 0.215 5	3.40 0.397 5	3.05 0.243 5	1.95 0.109 5	1.86 0.092 5	1.84 0.064 5	1.90 0.132 5
	Liver	Mean SD N	10.48 1.411 5	11.10 1.277 5	11.71 0.818 5	11.54 0.851 5	7.42 0.670 5	7.47 0.887 5	7.26 0.134 5	7.07 0.342 5
	Testes/ Epididymides	Mean SD N	3.94 0.358 5	4.48 0.156 5	4.44 0.465 5	4.17 0.320 5	-	-	-	-
	Ovaries	Mean SD N	-	-	-	-	0.0845 0.00831 5	0.0754 0.00765 5	0.0722 0.00801 5	0.0695 0.00479 5
Scheduled euthanasia Day 42 Recovery phase	Brain	Mean SD N	2.18 0.084 4	-	-	2.16 0.065 5	2.05 0.112 5	-	-	1.96 0.054 5
	Adrenals	Mean SD N	0.0682 0.01977 4	-	-	0.0501 0.00882 5	0.0657 0.01230 5	-	-	0.0708 0.00272 5
	Thyroids/ Parathyroid	Mean SD N	0.0219 0.00180 4	-	-	0.0164 0.00226 5	0.0136 0.00132 5	-	-	0.0156 0.00298 5
	Heart	Mean SD N	1.50 0.052 4	-	-	1.31 0.073 5	0.93 0.068 5	-	-	0.90 0.036 5
	Thymus	Mean SD N	0.50 0.168 4	-	-	0.43 0.093 5	0.36 0.030 5	-	-	0.37 0.097 5
	Spleen	Mean SD N	0.76 0.079 4	-	-	0.80 0.110 5	0.50 0.029 5	-	-	0.53 0.046 5
	Kidneys	Mean SD N	3.74 0.287 4	-	-	3.53 0.308 5	1.98 0.101 5	-	-	2.00 0.264 5
	Liver	Mean SD N	13.14 1.371 4	-	-	12.42 0.642 5	7.27 0.617 5	-	-	7.13 0.252 5
	Testes/ Epididymides	Mean SD N	4.34 0.319 4	-	-	4.15 0.510 5	-	-	-	-
	Ovaries	Mean SD N	-	-	-	-	0.0766 0.00671 5	-	-	0.0764 0.01007 5

Applicant's summary and conclusion

Conclusions:

Based on the results of this study, a dosage level of 1000 mg/kg/day was considered to be the no-observed-effect level (NOEL) following 28-day oral administration of the test substance to rats.

Executive summary:

The purpose of this study was to evaluate the potential toxicity of the test substance when administered orally, by gavage, to rats for 28 consecutive days followed by a 14-day recovery phase. The study design consisted of a control group and three treatment groups with ten animals per sex in the control and high-dose groups and five animals per sex in the low- and mid-dose groups. The test article in the vehicle was administered as a single daily dose at dosage levels of 100, 500 and 1000 mg/kg/day for 28 consecutive days. Control animals received the vehicle (10% w/v mixture of polysorbate 80 and polyethylene glycol 400) under the same experimental conditions. Cage-side observations were performed daily, between 30-120 minutes following dosing, and daily during the recovery phase. A functional observation battery was performed on days -1 , 5,12,19, 26/27/28 and 40 for each animal. Individual body weights were recorded on days -2, 8,15, 22, 28, 35 and 41. In addition, a terminal body weight was recorded on the day of scheduled euthanasia (day 29 or 42). Food consumption was recorded on days -2,8,15, 22, 28, 35 and 41. Blood and urine samples were obtained from all animals on the day of scheduled euthanasia (day 29 or 42) for evaluation of selected clinical pathology parameters. Ophthalmology examinations were performed on all animals on days 23 and 40. Each rat was subjected to a complete gross necropsy examination at the time of death or scheduled euthanasia (day 29 or 42). Five males and five females per group were euthanized at the end of the treatment phase (day 29). The remaining males and females in the control and high-dose groups were euthanized at the end of the recovery phase (day 42). Fresh organ weights were obtained for all animals at scheduled euthanasia and selected tissues were preserved from all rats. All tissues and organs collected at necropsy from animals in the control and high-dose groups were examined microscopically. Oral administration of the test article to rats did not produce any treatment-related mortalities. One control male was found dead on day 23 from a bladder calculi. However, this death was not considered treatment-related since Itoccurred In a control animal and apparently was a result of renal failure that was secondary to the bladder calculi. No treatment-related clinical abnormalities, bodyweight effects, food consumption abnormalities or ophthalmologlcal findings were noted during the main or recovery phases of this study. Weekly neurotoxicological evaluations of the animals did not reveal any notable abnormalities. FOB examinations conducted prior to dosing were consistent between control and treated animals and no notable abnormalities were observed in any animal during the recovery phase. No treatment-related abnormalities were observed in the clinical pathology parameters evaluated or organ weight data. In addition, there was no evidence of treatment-related effects on the organs or tissues as determined by histopathological evaluation. Based on the results of this study, a dosage level of 1000 mg/kg/day was considered to be the no-observed-effect level (NOEL) following 28-day oral administration of the test substance to rats.