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Repeated dose toxicity: oral

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Administrative data

Endpoint:
sub-chronic toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From Mar. 15, 2004 to Nov. 30, 2005
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study well documented, followed guideline, GLP

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2005
Report Date:
2005

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity in Rodents)
Deviations:
no
GLP compliance:
yes
Remarks:
according to U.S. FDA and OECD principles of GLP
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Details on test material:
- Name of test material: N,N-bis (2-hydroxyethyl)-p-phenylenediamine sulfate
- TSIN: GTS03849
- Substance type: Pure active substance
- Physical state: White powder
- Stability under test conditions: Not reported
- Storage condition of test material: At room temperature, Protected from light.

Test animals

Species:
rat
Strain:
other: Crl:CD(SD)IGS BR
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories, Portage, Michigan.
- Age at study initiation: Approx. 6-7 Wk
- Weight at study initiation: 204-299 g (males) and 153-194 g (females)
- Fasting period before study: No
- Housing: Individually, in suspended stainless-steel cages. The animals were given various cage-enrichment devices as a form of environmental enrichment.
- Diet: Certified rodent diet (#8728C, Harlan Teklad); ad libitum (except when animals were fasted for clinical pathology or necropsy procedures).
- Water: Ad libitum
- Acclimation period: 7 d
- The manufacturer analyzed the diet for nutritional components and environmental contaminants. Water samples were routinely analyzed for specified microorganisms and environmental contaminants. No contaminants were known to be present in the diet or water at levels which might have interfered with result of this study.

ENVIRONMENTAL CONDITIONS
- Temperature: 19-25°C
- Humidity: 30-70%
- Air changes: 10 or greater air changes/h
- Photoperiod: 12 h light/12 h dark cycle per d

IN-LIFE DATES: From: Mar. 22, 2004 To: July. 19, 2004

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
other: 0.2% w/v erythorbic acid in reverse osmosis water
Details on oral exposure:
PREPARATION OF DOSING SOLUTIONS: For each dose formulation, the required amount of test substance was added to a volume of vehicle and mixed on a magnetic stirrer until the formulation appeared to be a solution. Additional vehicle was added to achieve the final volume. The formulations were transferred to individual amber glass containers for daily use.
All dose solutions were allowed to come to room temperature prior to dosing.
- Rate of preparation of formulation (frequency): Dose formulations were prepared approx. weekly
- Storage temperature of formulation: Stored in a refrigerator set to maintain 2 to 8°C, protected from light

VEHICLE
- Justification for use and choice of vehicle: Not reported
- Concentration in vehicle: 0.1, 0.4 and 2 mg/mL for 1.0, 4.0 and 20 mg/kg bw/day respectively.
- Amount of vehicle: 10 mL/kg, individual dose volume was based on the most recently recorded body weight.
- Lot/batch no. (Erythorbic acid): Sigma-Aldrich, Lot# 122K0539
- Purity (Erythorbic acid): 99.9%
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Analyses were performed using high-performance liquid chromatography. The method was developed by the sponsor and modified and validated by Covance-Madison (Covance method MA-PG61-2050). For concentration determination, acceptance criteria for results of mean values were ±15% of the theoretical concentration.
1. Homogeneity:
Homogeneity of the test substance in vehicle was established on the first preparation used in this study. Duplicate samples (5 mL each) were taken from the top, middle, and bottom of the highest and lowest concentration dose solutions. Samples were maintained at room temperature protected from light and analyzed on the day of preparation. Mean results of the homogeneity analyses of the top, middle, and bottom locations of the low and high dose concentrations (0.1 and 2.0 mg/mL, respectively) ranged from 96.6 to 97.0% and 98.5 to 99.5% of theoretical, respectively, indicating that the mixing procedure resulted in homogeneous preparations.
2. Concentration verification:
Analyses of the concentration verification were performed from the first preparation used for dosing during weeks 2, 5, 9 and 13. Duplicate samples (5 mL each) were taken from the middle of each solution for concentration determination. For the first preparation used on study, the mean concentration obtained in the homogeneity determination for the middle sample from the lowest and highest concentration dose solution served as the concentration verification value. Dose confirmation mean results for all concentrations ranged from 96.6 to 98.5%, 96.8 to 99.5%, 97.7 to 99.7%, 98.6 to 99.5%, and 74.7 to 90.8% of theoretical for Weeks 1 (initial), 2, 5, 9, and 13, respectively. Results of the Wk 13 analysis of the 0.1-mg/mL concentration did not meet acceptance criteria (within 15% of theoretical).
3. Stability:
The stability of the test substance in the vehicle was established in Covance 6114-461 for the concentration range used in the study. Results of stability analyses indicated that the formulations were stable in the vehicle for up to 7 d under refrigerated storage conditions.
Duration of treatment / exposure:
91 d; 5 animals/sex in control and high dose group underwent 91 d of treatment followed by at least 4 weeks of recovery.
Frequency of treatment:
Daily
Doses / concentrationsopen allclose all
Dose / conc.:
1 mg/kg bw/day (actual dose received)
Dose / conc.:
4 mg/kg bw/day (actual dose received)
Dose / conc.:
20 mg/kg bw/day (actual dose received)
No. of animals per sex per dose:
15 animals/sex/group; additional 5 animals/sex were included in control and high dose group as recovery group animals.
-Five extra animals/sex received in the animal shipment but not assigned to the study underwent both the pre-study
Expanded Clinical Observations and Motor Activity testing to establish baseline values in case replacement animals were needed.
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: The doses selected for this study were based on the results of a 14-day range-finding study (Covance 6114-469).
- Rationale for animal assignment: Post acclimation, animals were randomized into four groups using a computerized blocking procedure designed to achieve body weight balance with respect to treatment groups. After assignment to groups, the mean body weight for each group of each sex was not statistically different at the 5.0% probability level. At randomization, the coefficient of variation of the mean weight for each sex and group did not exceed 10%.
- Rationale for selecting satellite groups: 5 animals/sex were included in control and high dose group to assess the reversibility of any effects after a recovery period.
- Post-exposure recovery period in satellite groups: 4 Wk
- Assignment of animals: The animals were assigned into following control and treatment groups:
Group 1(vehicle control): 0 mg/kg bw/day
Group 2 (Low dose): 1 mg/kg bw/day
Group 3(Mid dose): 4 mg/kg bw/day
Group 4 (High dose): 20 mg/kg bw/day
Positive control:
No

Examinations

Observations and examinations performed and frequency:
CLINICAL OBSERVATIONS: Yes, each animal was observed for mortality, abnormalities and signs of pain or distress; findings were recorded as they were observed.
- Time schedule: Twice daily (a.m. and p.m.)

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Once daily
- Cage side observations included: Abnormal findings were recorded

DETAILED CLINICAL OBSERVATIONS: Yes, these observations were made outside the home cage and included, but were not limited to, changes in skin, fur, eyes, and mucous membranes; occurrences of secretions and excretions; and autonomic activity (e.g., lacrimation, piloerection, pupil size, unusual respiratory pattern). Changes in posture and reactivity to handling and the presence of clonic or tonic movements, stereotypes (e.g., excessive grooming, circling), or bizarre behavior (e.g., self-mutilation, walking backwards) were also recorded. Changes in gait were assessed by allowing the animal to walk freely to allow evaluation of gait. Additional findings were recorded as they were observed.
- Time schedule: Prior to treatment, on Day 1, weekly thereafter, and on the day of each scheduled sacrifice

BODY WEIGHT: Yes
- Time schedule for examinations: Individual body weights were recorded twice prior to treatment, on the first day of treatment, and weekly thereafter.

FOOD CONSUMPTION: Yes
- Time schedule for examinations: Weekly

FOOD EFFICIENCY: No

WATER CONSUMPTION AND COMPOUND INTAKE: No

OPHTHALMOSCOPIC EXAMINATION: Yes, Animals were examined by a board-certified veterinary ophthalmologist using an indirect ophthalmoscope and a slit lamp. The eyes were dilated with a mydriatic agent prior to examination.
- Time schedule for examinations: Prior to treatment in a sequential manner and during Wk 13 in random order. The ophthalmic examinations were done on a day other than that scheduled for the expanded clinical observations.
- Dose groups that were examined: All animals

HAEMATOLOGY: Yes, blood samples for were collected from a jugular vein of animals.
- Time schedule for collection of blood: At each scheduled sacrifice (on Day 92 and on Day 120)
- Anaesthetic used for blood collection: No
- Anticoagulants used: Yes potassium EDTA (for hematology) and sodium citrate (for coagulation parameters)
- Animals fasted: Yes (overnight)
- How many animals: All surviving animals
- Parameters examined: Red blood cell (erythrocyte) count, hemoglobin, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, platelet count, white blood cell (leukocyte) count, differential blood cell count, blood smear, reticulocyte count, prothrombin time and activated partial thromboplastin time.

CLINICAL CHEMISTRY: Yes, blood samples for were collected from a jugular vein of unanesthetized animals.
- Time schedule for collection of blood: At each scheduled sacrifice (on Day 92 and on Day 120)
- Animals fasted: Yes (overnight)
- How many animals: All surviving animals
- Parameters examined: Glucose, urea nitrogen, creatinine, total protein, albumin, globulin, albumin/globulin ratio, cholesterol, total bilirubin, alanine aminotransferase, alkaline phosphatase, gamma glutamyl transferase, aspartate amino transferase, calcium, inorganic phosphorus, sodium, potassium and chloride.

URINALYSIS: Yes, urine specimens were collected on wet ice
- Time schedule for collection of urine: At each scheduled sacrifice (on Day 92 and on Day 120).
- Metabolism cages used for collection of urine: Yes, individual urine collection cages were used
- Animals fasted: Yes (overnight)
- Parameters examined: Specific gravity, pH, protein, glucose, ketones, bilirubin blood, urobilinogen, volume, microscopic examination of sediment, appearance/color and urine chemistry (Sodium, potassium, chloride, sodium excretion, potassium excretion and chloride excretion).

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: Hand-held and open-field expanded clinical observations were done once prestudy and during Wk 4, 8, and 13 (in random order); elicited behavior observations were done once prestudy and during Wk 13 (in random order); and motor activity data were collected prestudy and during Wk 13. Expanded clinical observations and motor activity testing were done on a day other than that scheduled for the weekly detailed clinical observations
- Dose groups that were examined: 10 animals/sex/group (same animals were tested for all the three battery of functions)
- Battery of functions tested: Hand-held and open-field expanded clinical observations, elicited behavior observations, and motor activity. Additional findings were recorded as they were observed.
Sacrifice and pathology:
SACRIFICE: On Day 92, up to 15 animals/sex/group were fasted overnight, anesthetized with carbon dioxide, weighed, and exsanguinated. On Day 120, (after 4 Wk recovery), all surviving animals in Groups 1 and 4 were fasted overnight, anesthetized with carbon dioxide, weighed, and exsanguinated.
GROSS PATHOLOGY: Yes, each animal sacrificed, or died during the study was necropsied. The necropsy included an examination of the external features of the carcass; external body orifices; the abdominal, thoracic, and cranial cavities; organs; and tissues.
- Tissues from each animal (when present) were preserved in 10% neutral-buffered (except testis-preserved in Bouin’s fixative): Adrenal (2), aorta, brain (cerebrum, cerebellum, and medulla), cecum, cervix, colon (proximal and distal (2)), duodenum, epididymis (2), esophagus, eye (2), femur with bone marrow (articular surface, of the distal end), Harderian gland, heart, ileum (including Peyer’s patch), jejunum, kidney (2), lacrimal gland (exorbital), liver, lung with mainstem bronchi, lymph node (mandibular and mesenteric), mammary gland (females), nasal turbinates, ovary (2), pancreas, pituitary gland, prostate, rectum, salivary gland (mandibular (2)), sciatic nerve, seminal vesicle (2), skeletal muscle (thigh), Skin, spinal cord (cervical, thoracic, and lumbar), spleen, sternum with bone marrow, stomach (nonglandular and glandular), testis (2), thymus, thyroid with parathyroid, tissues with macroscopic changes, or alterations (i.e., gross lesions), tongue, trachea, urinary bladder, uterus with uterine horns vagina and zymbal’s gland.
HISTOPATHOLOGY: Yes, preserved tissues from each animal in the control and high-dose groups at the terminal sacrifice and those that died during the study were embedded in paraffin, sectioned, stained with hematoxylin and eosin, and examined microscopically. Macroscopic lesions were also examined microscopically from each animal in the low- and mid-dose groups.
Testes and epididymides from each terminal sacrifice male in the control and high-dose groups were examined microscopically by a board-certified veterinary pathologist:
- Following collection from each male at each scheduled sacrifice, the epididymis was separated from the testes. After adequate fixation in 10% neutral buffered formalin, each testis was sectioned transversely in half, and the cranial pole was sectioned for routine embedding in paraffin, histologic processing, and staining with hematoxylin and eosin. The remaining testicular tissue was stored in 70% ethyl alcohol.
- The epididymides were sectioned longitudinally and processed routinely for histologic evaluation. This longitudinal section should ensure that the head and mid portion of the epididymides were evaluated histologically. The remaining portions of the epididymides were stored in 10% neutral-buffered formalin.

PATHOLOGY PEER REVIEW:
A peer review of microscopic findings was performed by a board-certified veterinary pathologist at Pathology Associates (PAI). The peer review was performed according to the reviewer’s standard operating procedures.
Other examinations:
ABSOLUTE AND RELATIVE ORGAN WEIGHT: At scheduled sacrifice, the following organs (when present) were weighed; paired organs were weighed together: adrenal (2), brain, epididymis (2), heart, kidney (2), liver, lung, ovary (2), pituitary gland, prostate, salivary gland (mandibular (2)), seminal vesicle (2), spleen, testis (2), thymus, thyroid (2) with parathyroid, uterus. Organ-to-body weight percentages and organ-to-brain weight ratios were calculated.

VAGINAL CYTOLOGY: Daily vaginal smears were prepared and examined to evaluate the stage of the estrous cycle for each female.
- Time schedule for examinations: Daily for 21 consecutive days beginning after Wk 10 (Days 71 through 91). For each animal, the estrous stage was documented each day for the 21 consecutive d.
- How many animals: All surviving females were evaluated

MALE REPRODUCTIVE ASSESSMENT: At each scheduled sacrifice, male reproductive assessment (sperm motility, sperm morphology, and total sperm count) was done by Pathology Associates (PAI).
The details on male reproductive assessment procedures are provided in the study report.
Statistics:
1. The following statistical methods were used to analyze the body weight, body weight change, food consumption, motor activity, grip strength, nociceptive reflex, continuous clinical pathology, and organ weight data:
- Levene’s test was done to test for variancehomogeneity. In the case of heterogeneity of variance at p < 0.05, rank transformation was used to stabilize the variance. Comparison tests took variance heterogeneity into consideration.
- One-way analysis of variance was used to analyze data.
- If the ANOVA was significant (p < 0.05), Dunnett’s t-test was used for control versus treated group comparisons.
2. The length of an estrus cycle for individual animals was determined by counting the number of days from a recording of estrus (including this first day of estrus) up to (but not including) the next recording of estrus that occurs after metestrus, diestrus, or proestrus are recorded. The mean estrus cycle duration (i.e., number of days) was calculated for each animal. Group means and standard deviations for estrus cycle duration were calculated and reported.
For estrus cycle evaluations, the total number of days in each phase, the number of combined days in proestrus and estrus, and the number of combined days in metestrus and diestrus were calculated for each animal. Group means and standard deviations for these parameters were calculated and reported.
3. The following statistical methods were used to analyze the sperm motility, total count, and sperm morphology data:
- The data were analyzed by the Kruskal-Wallis H-test (nonparametric ANOVA).
- If the Kruskal-Wallis H-test was significant, the Wilcoxon-Mann-Whitney two-sample rank sum test was used to compare each treated group with the control group.
For each sex, Groups 2 through 4 were compared with Group 1 (control) at the 5%, two-tailed probability level.

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
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
no effects observed
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Behaviour (functional findings):
no effects observed
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
no effects observed
Neuropathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
not examined
Details on results:
CLINICAL SIGNS AND MORTALITY: One Group 1 (vehicle control) male died on Day 72 from causes unrelated to treatment (severe, acute pyelonephritis). All other animals survived in apparent good health until scheduled sacrifice.
- No treatment-related clinical observations were noted during the treatment or recovery phase of the study. The few clinical observations noted for surviving animals (malocclusion, missing teeth, barbering, oral discharge, few feces, red haircoat, and sores or scabs) were unrelated to dose, were of small incidence and short duration, and therefore, were not considered treatment related.

BODY WEIGHT AND WEIGHT GAIN: Mean body weights and body weight changes of treated animals were comparable with controls throughout the treatment and recovery periods.

FOOD CONSUMPTION: No treatment-related effects on food consumption were noted during treatment and recovery.

OPHTHALMOSCOPIC EXAMINATION: There were no treatment-related ophthalmic observations

HAEMATOLOGY: Very few statistically significant or otherwise notable differences for clinical pathology test results were observed between the control and treated animals. None of the differences in the haematology parameters were attributable to treatment with test substance.

CLINICAL CHEMISTRY: Statistically significantly higher triglyceride concentration was observed in mid dose females at Wk 14. However, this variation was considered incidental, as the difference was extremely small (i.e., only 6 mg/dL), males were unaffected, and there were no correlative findings. The difference for triglyceride concentration was consistent with normal biological variation.

URINALYSIS: None of the differences in the urinalysis parameters were attributable to treatment with test substance.

NEUROBEHAVIOUR: No test substance-related effects on neurobehavioral assessment tests were apparent during treatment. Motor activity was significantly decreased at the 30-40 and 0-40 minute intervals for high dose group females. However, because values recorded during acclimation were also lower for high dose group females compared with controls and because a similar effect was not seen in males, these decreases were not considered to be toxicologically important.

ORGAN WEIGHTS: Terminal organ weight and organ to body weight ratio were not affected by treatment. Decreased mean absolute testicular and thymic weight values were observed in high dose group recovery males. However, there was no histological correlate to support this finding and were not attributed to the treatment.

GROSS PATHOLOGY: No treatment related differences were observed in macroscopic findings.

HISTOPATHOLOGY: NON-NEOPLASTIC: All histological findings were of the kind commonly found in laboratory rats of age and strain used in the study or were of singular occurrence or distributed (scattered) randomly among the groups without relation to dosage.

OTHER FINDINGS:
- Vaginal Cytology: The mean number of days in each stage and the mean estrus cycle duration was comparable across groups.
- Male Reproductive Assessment: The mean percent sperm motility, caudal epididymal sperm count, and sperm morphology were not affected by treatment. No biologically meaningful differences were observed between the study groups.

Effect levels

Key result
Dose descriptor:
NOAEL
Effect level:
20 mg/kg bw/day (actual dose received)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: overall effects

Target system / organ toxicity

Key result
Critical effects observed:
no

Applicant's summary and conclusion

Conclusions:
Administration of N,N-bis (2-hydroxyethyl)-p-phenylenediamine sulfate to Crl:CD(SD)IGS BR rats at dose levels of 0, 1, 4 and 20 mg/kg bw/day by oral gavage over a period of 91 d did not elicit any toxic response at any of the dose levels tested.
The No Observed Adverse Effect Level (NOAEL) for subchronic oral toxicity of test substance was determined to be higher than 20 mg/kg bw/day.
Executive summary:

Subchronic toxicity of N,N-bis (2-hydroxyethyl)-p-phenylenediamine sulfate was performed following OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity in Rodents).

The study was designed to evaluate the toxicity of the test substance, when administered daily at dose levels of 0, 1, 4 and 20 mg/kg bw/day via oral gavage to Crl:CD(SD)IGS BR rats for 91 d and to assess the reversibility of any effects after a 4 Wk recovery period.

A total of 140 Crl:CD(SD)IGS BR rats (70/sex) of 6-7 Wk age (source: Charles River Laboratories, Portage, Michigan), weighing 204-299 g (males) and 153-194 g (females) were housed individually, in suspended stainless-steel cages. The animals were maintained under standard laboratory conditions (temperature: 19-25°C, relative humidity: 30-70%, 10 or greater air changes/h, 12 h light/12 h dark cycle per d). The animals were fed on certified rodent diet (#8728C, Harlan Teklad); ad libitum and acclimated to laboratory condition for a period of 7 d.

Dose formulations were prepared weekly, stored in a refrigerator set to maintain 2 to 8°C and protected from light. For each dose level, the required amount of test substance was added to a volume of vehicle (0.2% w/v erythorbic acid in reverse osmosis water) and mixed on a magnetic stirrer until the formulation appeared to be a solution.

Post acclimation, animals were randomized into four treatment and one vehicle control group (containing 15 animal/sex/ group each) using a computerized blocking procedure designed to achieve body weight balance with respect to treatment groups. An additional 5 animals/sex were included in control and high dose groups to assess the reversibility of any effects after a 4 Wk recovery period.

The animals were observed twice daily (a.m. and p.m.) for mortality, abnormalities, and signs of pain or distress. Cage side observations were made for each animal once daily. Detailed clinical observations were performed prior to treatment, on Day 1, weekly thereafter, and on the day of each scheduled sacrifice. Neurobehavioral observations were performed weekly; hand-held and open-field expanded clinical observations were done pre-study and during Weeks 4, 8, and 13; elicited behavior observations were done prestudy and during Wk 13; and motor activity data were collected pre-study and during Wk 13. Ophthalmic examinations were done prior to treatment and during Wk 13. Body weights were collected twice prior to treatment, on Day 1, and weekly thereafter. Food consumption data were measured weekly. Vaginal cytology data were collected once daily for 21 consecutive days, beginning after Wk 10. Blood and urine samples for hematology, coagulation, clinical chemistry, urinalysis, and urine chemistry were collected at each scheduled sacrifice (on Day 92 and Day 120).

 

On Day 92, up to 15 animals/sex/group were anesthetized, weighed, and necropsied. On Day 120, all surviving animals (recovery group) were anesthetized, weighed, and necropsied. Each animal sacrificed, or died during the study was necropsied, selected organs were weighed and selected tissues collected and preserved. At each scheduled sacrifice, male reproductive assessment (sperm motility, morphology, and count) was done by Pathology Associates (PAI). Microscopic examination of tissues was performed, and a pathology peer review was conducted.

 

One Group 1 (vehicle control) male died on Day 72 from causes unrelated to treatment (severe, acute pyelonephritis). All other animals survived in apparent good health until scheduled sacrifice. No treatment-related clinical observations were noted during the treatment or recovery phase of the study.

There were no test substance-related effects on ophthalmic observations; effects on neurobehavioral assessment tests; effects on body weights or body weight changes; effects on food consumption; or effects on vaginal cytology. Test substance had no effect on clinical pathology test results.

The mean percent sperm motility, caudal epididymal sperm count, and sperm morphology were not affected by treatment. No biologically meaningful differences were observed between the study groups.

 

Based on the results of the study, the No Observed Adverse Effect Level (NOAEL) following oral gavage administration of N,N-bis (2-hydroxyethyl)-PPD Sulf to rats at doses of 0, 1, 4, or 20 mg/kg/day for 91 d was determined to be greater than 20 mg/kg/day.

 

This repeated dose toxicity study is classified as acceptable, and satisfies the guideline requirements of OECD 408 method.