Registration Dossier

Administrative data

Endpoint:
short-term repeated dose toxicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Study period:
17 June 2004 - 27 Sept 2004
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Referenceopen allclose all

Reference Type:
study report
Title:
Unnamed
Year:
2004
Report Date:
2004
Reference Type:
study report
Title:
Unnamed
Year:
2004

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 407 (Repeated Dose 28-Day Oral Toxicity in Rodents)
Version / remarks:
July 27, 1995
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.7 (Repeated Dose (28 Days) Toxicity (Oral))
Version / remarks:
September 30, 1996
Deviations:
no
Qualifier:
according to
Guideline:
other: Japanese Guidelines for Screening, Toxicity Testing of Chemicals : Testing Methods for new Substances
Version / remarks:
December 5, 1986
Deviations:
no
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent

Test animals

Species:
rat
Strain:
Wistar
Remarks:
HanBrl:WIST
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: RCC Ltd, Laboratory Animal Services CH-4414 Fullinsdorf / Switzerland
- Age at study initiation: 6 weeks
- Weight at study initiation:
Males: 132.9 - 152.0 grams (mean 139.8 grams)
Females: 115.0 -129.5 grams (mean 120.2 grams)
- Housing: In groups of five in Makrolon type-4 cages with wire mesh tops and standardized softwood bedding.
- Diet: ad libitum, Pelleted standard Provimi Kliba 3433 rat maintenance diet
- Water: ad libitum, community tap-water
- Acclimation period: 7 days

DETAILS OF FOOD AND WATER QUALITY: None of the contaminants analyzed in the water and diet is considered to have been present at a concentration that would have affected the validity of the results.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3
- Humidity (%): 30-70
- Air changes (per hr): 10-15
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
polyethylene glycol
Remarks:
PEG 300
Details on oral exposure:
PREPARATION OF DOSING SOLUTIONS:
The test item formulations were prepared weekly. The test item was weighed into a glass beaker on a tared Mettler balance and the vehicle added. The mixtures were prepared using a magnetic stirrer and stored at room temperature (19-25°C).
Homogeneity of the test item in the vehicle was maintained during the daily administration period using a magnetic stirrer.

Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
First analysis: The mean concentrations of the homogeneity samples taken during pretest preparations were found to be 92.2%, 110.3% and 112.9% of the nominal concentrations of dose group 2 (10 mg/mL), dose group 3 (30 mg/mL), and dose group 4 (90 mg/mL), respectively. The individual concentrations varied in the range from -8% to +7% of the mean concentrations. Therefore, the test item was found to be homogeneously distributed in the vehicle.
Second analysis: The mean concentrations of the homogeneity samples were found to be 109.0%, 108.0%, and 95.8% of the nominal concentrations of dose group 2 (10 mg/mL), dose group 3 (30 mg/mL), and dose group 4 (90 mg/mL), respectively. The individual concentrations varied in the range from -3% to +2% of the mean concentrations. Therefore, the test item was found to be homogeneously distributed in the vehicle.
Duration of treatment / exposure:
28 days (+ 14 days recovery)
Frequency of treatment:
daily
Doses / concentrationsopen allclose all
Dose / conc.:
50 mg/kg bw/day (nominal)
Dose / conc.:
150 mg/kg bw/day (nominal)
Dose / conc.:
450 mg/kg bw/day (nominal)
No. of animals per sex per dose:
10
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale:
Based upon the results of a non-GLP 5-day dose-range-finding study (RCC Study Number 854323) in which the test item was administered by gavage to 2 rats per group and sex.

GENERAL
In the dose range-finding toxicity study, the test item was administered daily by oral gavage to SPF-bred Wistar rats of both sexes at dose levels of 30, 150 or 750 mg/kg body weight for a period of five days. A control group received a similar dose volume (5 mL/kg body weight) of the vehicle, PEG 300. The study comprised two animals per group and sex which were sacrificed after five days of treatment. Clinical signs, food consumption and body weights were recorded periodically during the acclimatization and treatment periods. At the end of the dosing period, all animals were killed, necropsied and examined post mortem. The results of the study are summarized as follows:

Mortality
Female no. 16 (750 mg/kg/day) was found dead on treatment day 3. All other animals
survived until scheduled necropsy.

Clinical Signs
There were no clinical signs evident at any dose level.

Food Consumption
The mean daily food consumption of the test item-treated males compared favorably with that of the control males. The mean daily food consumption of the females treated with 750 mg/kg/day was markedly reduced from days 3-5 of treatment.

Body Weights
No test item-related changes in mean body weights were noted at any dose level.

Organ Weights
Elevated liver-to-body weight ratios were noted in males and females treated with 750 mg/kg/day when compared with the controls. Elevated kidney-to-body weight ratios were noted in males treated with 750 mg/kg/day, whereas elevated spleen-to-body weights were seen in the remaining female treated with 750 mg/kg/day. No organ weight changes of toxicological relevance were noted at any other dose level.

Macroscopical Findings
Red thymic foci were noted in one female treated with 30 mg/kg/day and one female treated with 150 mg/kg/day. The one female treated with 750 mg/kg/day which was found dead (no.16) on treatment day 3 was without macroscopical changes; a cause of death could not beestablished.

ASSESSMENT
Based on the results of the five-day dose range-finding study, dose levels of 50, 150 or 450 mg/kg body weight/day are proposed for the 28-day study (RCC Study Number 854324).
Positive control:
none

Examinations

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily
The animals were observed for clinical signs once before commencement of administration; twice daily on days 1-3; as well as once daily on days 4-28 and once daily during days 29-42 (recovery).

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: weekly
The animals were observed in their home cages, outside their home cages in a standard arena and in the hand. These observations were performed in random sequence once before commencement of administration and once weekly (weeks 1-3) thereafter.

BODY WEIGHT: Yes
- Time schedule for examinations: weekly
Body weights were recorded weekly during pretest, treatment and recovery and before necropsy, using an on-line electronic recording system consisting of a Mettler balance.

FOOD CONSUMPTION AND COMPOUND INTAKE: Yes
The food consumption was recorded once during the pretest period and weekly thereafter, using an on-line electronic recording system consisting of a Mettler balance.

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: after 4 weeks and after 6 weeks
- Anaesthetic used for blood collection: Yes, light isoflurane anesthesia
- Animals fasted: Yes
- How many animals: all
- Parameters examined: Erythrocyte count, Reticulocyte count, Hemoglobin, Reticulocyte maturity index, Hematocrit, Methemoglobin, Mean corpuscular volume, Total leukocyte count, Red cell volume distribution with Differential leukocyte count, Mean corpuscular hemoglobin, Coagulation, Mean corpuscular hemoglobin concentration, Thromboplastin time, Hemoglobin concentration, distribution width, Activated partial thromboplastin time, Platelet (thrombocyte) count

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: after 4 weeks and after 6 weeks
- Animals fasted: Yes, light isoflurane anesthesia
- How many animals: all
- Parameters examined: Glucose, Urea, Creatinine, Bilirubin, total Cholesterol, total Triglycerides, Phospholipids, Aspartate aminotransferase, Alanine aminotransferase, Lactate dehydrogenase, Glutamate dehydrogenase, Creatine kinase,
Alkaline phosphatase, Gamma-glutamyl-transferase, Sodium, Potassium, Chloride, Calcium, Phosphorus inorganic Protein, total Albumin, Globulin, Albumin/Globulin ratio, Bile acids

URINALYSIS: Yes
Urine was collected during the 18-hour fasting period into a specimen vial after 4 weeks and after 6 weeks.
The following urinalysis parameters were determined: Volume (18 hours), Glucose, Specific gravity (relative density), Ketones, Color, Urobilinogen, Appearance, Bilirubin, pH, Erythrocytes, Nitrite, Leukocytes, Protein

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations: During week 4, relevant parameters from a modified Irwin screen test were evaluated in all animals.
- Dose groups that were examined: all
- Battery of functions tested: grip strength / locomotor activity

IMMUNOLOGY: No
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
All animals were anesthetized by intraperitoneal injection of sodium pentobarbitone and killed by exsanguination. Samples of the following tissues and organs were collected from all animals at necropsy and fixed in neutral phosphate buffered 4 % formaldehyde solution (unless otherwise indicated):
Adrenal glands, Aorta, Bone (sternum, femur including joint), Bone marrow (femur), Brain (3 levels), Cecum, Colon, Duodenum, Epididymides (fixed in Bouin's solution), Esophagus, Eyes with optic nerve (fixed in Davidson's solution), Harderian gland (fixed in Davidson's solution), Heart, Ileum, with Peyer's patches, Jejunum with Peyer's patches, Kidneys, Larynx, Lacrimal gland (exorbital), Liver, Lungs (infused with formalin at necropsy), Lymph nodes (mesenteric, mandibular), Mammary gland area Nasal cavity, Ovaries, Pancreas, Pituitary gland, Prostate gland, Rectum, Salivary glands (mandibular, sublingual), Sciatic nerve, Seminal vesicles, Skeletal muscle, Skin, Spinal cord (cervical, midthoracic, lumbar), Spleen, Stomach, Testes (fixed in Bouin's solution), Thymus, Thyroid (incl. parathyroid gland), Tongue, Trachea, Urinary bladder (infused with formalin at necropsy), Uterus, Vagina, Gross lesions

ABSOLUTE AND RELATIVE ORGAN WEIGHTS
The following organ weights were recorded on the scheduled dates of necropsy:
Brain, Thymus, Spleen, Ovaries, Heart, Kidneys, Testes, Liver, Adrenals, Epididymides

HISTOPATHOLOGY: Yes
Slides of organs and tissues that were collected at scheduled sacrifice from the animals of control and high-dose groups, as well as livers of low and middle dose groups, were examined.
Statistics:
The following statistical methods were used to analyze the grip strength, locomotor activity, body weight, organ weights and ratios, as well as:
• The Dunnett-test (many to one t-test) based on a pooled variance estimate were applied if the variables could be assumed to follow a normal distribution for the comparison of the treated groups and the control groups for each sex.
• The Steel-test (many-one rank test) were applied instead of the Dunnett-test when the data can not be assumed to follow a normal distribution.
• Fisher's exact-test were applied to the macroscopic findings.
The following statistical methods were used for statistical analysis of clinical laboratory data:
• Quantitative data were analyzed by a one-way analysis of variance (ANOVA) when the variances are considered homogeneous according to Bartlett. Alternatively, if the variances are considered to be heterogenous (p<0.05), a non-parametric Kruskal-Wallis test was used. Treated groups were compared to the control groups using Dunnett's test if the ANOVA was significant at the 5% level and by Dunn's test in the case of a significant Kruskal-Wallis test (p<0.05).

Results and discussion

Results of examinations

Clinical signs:
effects observed, non-treatment-related
Description (incidence and severity):
No test item-related clinical signs of toxicological relevance were noted during daily observations.
Breathing noises were noted in one to three males at 450 mg/kg/day from days 13-28, and one female at 450 mg/kg/day on day 3 and again on days 21-22. As this finding was noted at low incidence, it was considered to be of no toxicological relevance. Breathing noises were, however, noted in one male for the first four days of the recovery period.
Salivation was observed on days 17 and 18 in females at 450 mg/kg/day and on day 26 in two male rats at 450 mg/kg/day. Soft feces were recorded on treatment day 18 in control and test item-treated rats, on treatment days 4 and 5 in female rats treated with 150 mg/kg/day, and on treatment day 17 in rats treated with 450 mg/kg/day. Emaciation was noted in one male rat at 450 mg/kg/day on day 28 of treatment. Because of their low incidence and intermittent occurrence, these findings were considered to be unrelated to the test item.
An open /scabbed wound was noted in one male treated with 450 mg/kg/day from days 8-28 of treatment. This finding was considered related to internecine conflict.
Mortality:
no mortality observed
Body weight and weight changes:
no effects observed
Description (incidence and severity):
The mean body weights of the test item-treated rats were unaffected.
Food consumption and compound intake (if feeding study):
no effects observed
Description (incidence and severity):
The mean daily food consumption of the test item-treated rats was unaffected.
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
effects observed, non-treatment-related
Description (incidence and severity):
No test item-related differences were noted in the hematology parameters after the treatment period and no late effects were seen after the recovery period.
Significantly reduced red blood cell counts were recorded after four weeks of treatment in females at 50 mg/kg/day (p<0.05) and 150 mg/kg/day (p<0.05). These differences were not dose-related and therefore considered to be unrelated to the test item.
Mean hemoglobin and hematocrit was significantly reduced in females treated with 50 mg/kg/day (p<0.05) and 450 mg/kg/day (p<0.05). A dose-response relationship was not observed as the values in females treated with 150 mg/kg/day exceeded that of the females treated with 450 mg/kg/day, and all remained within the ranges of the historical control values.
The mean relative basophil count was significantly elevated after four weeks of treatment in males treated with 450 mg/kg/day (p<0.05). Although females at this dose level were unaffected after the end of the treatment period, significantly elevated mean relative basophil counts (p<0.05) were noted after the recovery period. The relative monocyte count was elevated after the recovery period in females (p<0.05). All values remained within the ranges of the historical control data and were therefore considered to be incidental.
After the recovery period, hematocrit was significantly reduced in males (p<0.05) and the mean corpuscular hemoglobin concentration was significantly elevated in females (p<0.05).
As these parameters were unaffected after the end of the treatment period, the differences were considered to be incidental.
Clinical biochemistry findings:
effects observed, treatment-related
Description (incidence and severity):
When compared with the controls, significantly elevated cholesterol and phospholipid levels were noted after the treatment period in males and females treated with 450 mg/kg/day (p<0.01), which also exceeded the respective ranges of the historical control data. Elevated phospholipids were also significant in females treated with 50 mg/kg/day (p<0.05) and 150 mg/kg/day (p<0.01), but remained within the ranges of the historical control data. These differences were no longer evident after the recovery period. Triglycerides were significantly elevated after the treatment and recovery periods in females (p<0.01) treated with 450 mg/kg/day when compared with the controls. Although triglycerides were also elevated after the treatment and recovery periods in males at this dose level, the difference did not attain statistical significance, and all differences in triglycerides remained within the ranges of the historical control data. These differences were considered to be non-specific test item-related changes possibly related to metabolic adaptive changes in the liver.
Aspartate aminotransferase activity was significantly reduced after the treatment period in females treated with 150 mg/kg/day and 450 mg/kg/day, whereas it was increased in males treated with 450 mg/kg/day (p<0.05). These contrary findings remained within the ranges of the historical control values and considered to be incidental. Similarly, significantly reduced alanine aminotransferase and glutamate dehydrogenase activities (p<0.05 and p<0.01, respectively) recorded after recovery in males treated previously with 450 mg/kg/day, were not seen after the end of the treatment period, and considered to be incidental.
Creatinine levels were significantly decreased in males treated with 150 mg/kg/day (p<0.05) and both sexes treated with 450 mg/kg/day (p<0.01 or p<0.05). Changes in electrolytes noted after the end of the treatment period (significantly increased calcium in males at 450 mg/kg/day (p<0.01) and females at 150 mg/kg/day (p<0.01) and 450 mg/kg/day (p<0.01); and significantly reduced chloride levels in females at 450 mg/kg/day (p<0.05). Protein levels were significantly elevated in females treated with 150 mg/kg/day (p<0.05) and 450 mg/kg/day (p<0.01), whereas albumin was significantly increased in females treated with 50 mg/kg/day (p<0.01), 150 mg/kg/day (p<0.01) and 450 mg/kg/day (p<0.01). The A/G ratios were significantly increased at 50 mg/kg/day (p<0.05), 150 mg/kg/day (p<0.01) and 450 mg/kg/day (p<0.01). All values remained within the ranges of the historical control values and these were considered to be incidental.
After the recovery period, total bilirubin was significantly reduced in males previously treated with 450 mg/kg/day (p<0.05). Significantly reduced potassium levels (p<0.05) were noted in these males as well. These differences were not seen after the treatment period and were considered to be incidental.
Urinalysis findings:
effects observed, non-treatment-related
Description (incidence and severity):
No test item-related differences were noted in the urinalysis parameters after the treatment period and no late effects were seen after the recovery period. The mean relative density after four weeks of treatment was significantly elevated in males treated with 450 mg/kg/day (p<0.01), but this value did not exceed that of the historical control data, nor was it seen in females and, therefore, it was considered to be incidental. Nitrates were present in the urine of females after the end of the recovery period, but this finding was considered to be due to a slight change in the control value and of no toxicological relevance.
Behaviour (functional findings):
effects observed, non-treatment-related
Description (incidence and severity):
No test item-related differences in the mean fore- or hindlimb grip strength were noted at any dose level tested. The mean hindlimb grip strength of the females treated with 450 mg/kg/day was significantly lower (p<0.05) than that of the control females. As the mean forelimb grip strength of these females was unaffected and the males compared favorably with the controls, this finding was considered unrelated to the test item.
No test item-related differences in the mean locomotor activity were noted at any dose level tested. Males treated with 450 mg/kg/day had significantly elevated mean locomotor activity during 0-10 minutes (p<0.01) and significantly reduced activity during 40-50 minutes (p<0.05). The total mean locomotor activity of these males compared favorably with those of the control males. In females treated with 50 mg/kg/day, the mean locomotor activity was significantly elevated during 30-40 minutes (p<0.05) when compared with the controls. These brief differences to the control values were considered to be fortuitous changes of no toxicological relevance.
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
effects observed, non-treatment-related
Description (incidence and severity):
After 4 Weeks:
Test item-related differences in organ weights after four weeks' treatment were restricted to increased liver weights in males and females treated with 150 mg/kg/day and 450 mg/kg/day. These differences were considered likely to have resulted from metabolic adaptation and were not considered to adverse changes. All other organ weights and ratios were considered to be unaffected. The observed differences were limited to significantly increased liver-to-body weight ratios at 150 mg/kg/day in females (p<0.01) and in both sexes at 450 mg/kg/day (p<0.01), as well as significantly increased liver-to-brain weight ratios in both sexes at 150 mg/kg/day (p<0.05) and 450 mg/kg/day (males p<0.05; females p<0.01). Additionally, females treated with 450 mg/kg/day had significantly elevated mean absolute liver weights (p<0.01) when compared with the controls.
The reduced mean absolute adrenal weights noted in the females treated with 50 mg/kg/day (p<0.05), 150 mg/kg/day (not significant) and 450 mg/kg/day (not significant) were not clearly dose-related and were not accompanied by morphological changes. Therefore, these differences (and those noted in the mean adrenal-to-body weight ratios) were considered to be incidental. Similarly, the significantly elevated mean heart-to-body weight noted in the females treated with 150 mg/kg/day (p<0.05) was not dose-related and also considered to be incidental.

After 6 Weeks:
Significantly elevated mean absolute and relative liver weights persisted in test item-treated females after the recovery period (p<0.01 or p<0.05), whereas the liver weights of males compared favorably with those of the control males. The differences noted in the females were considered to represent partial reversal insofar as hepatocellular hypertrophy was not seen microscopically.
Significantly elevated mean absolute spleen weights and spleen-to-brain weight ratios were noted in test item-treated males after the recovery period (p<0.01 or p<0.05). These findings were not accompanied by morphological changes and, therefore, considered incidental.


Gross pathological findings:
effects observed, non-treatment-related
Description (incidence and severity):
There was no gross lesion that could be attributed to treatment with the test item. All findings recorded were considered to be within the range of normal background lesions, which may be seen in rats of this strain and age. They consisted of size reductions of seminal vesicles, uterine dilation, renal pelvis dilation, and discolored foci in stomach and lungs.
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
effects observed, non-treatment-related
Description (incidence and severity):
There were no test item-related microscopical changes of toxicological relevance. The only test item-related changes were noted in the liver. There was minimal to slight hepatocellular hypertrophy (mainly centrilobular) in main test animals from both sexes at 150 and 450 mg/kg/day, whereby there was no further sign of liver effects, and the findings reverted completely after the recovery period. From the type, severity and distribution of all other findings recorded, there was no toxicologically significant difference between controls and treated animals.
Histopathological findings: neoplastic:
not examined

Effect levels

Key result
Dose descriptor:
NOAEL
Effect level:
450 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: highest dose tested, no adverse effects observed

Target system / organ toxicity

Key result
Critical effects observed:
no

Applicant's summary and conclusion

Conclusions:
The NOAEL after oral application was determined to be 450 mg/kg bw/day for males and females after 28 days administration to Wistar rats.
Executive summary:

In a subacute toxicity study according OECD TG 407, the test item was administered daily by oral gavage to SPF-bred Wistar rats of both sexes at dose levels of 50, 150 and 450 mg/kg body weight/day for a period of 28 days. A control group was treated similarly with the vehicle, PEG 300, only.

The groups comprised 5 animals per sex that were sacrificed after 28 days of treatment. Additional 5 rats per sex and group were used at 0 and 450 mg/kg. These animals were treated for 28 days and then allowed a 14-day treatment-free recovery period after which they were sacrificed.

Clinical signs, outside cage observation, food consumption and body weights were recorded periodically during pretest, the treatment and recovery periods. Functional observational battery, locomotor activity and grip strength were performed during week 4.

At the end of the dosing and the treatment-free recovery period, blood samples were withdrawn for hematology and plasma chemistry analyses. Urine samples were collected for urinalyses. All animals were killed, necropsied and examined post mortem. Histological examinations were performed on organs and tissues from all control and high dose animals, and all gross lesions from all animals.

All animals survived until scheduled necropsy. No test item-related clinical signs of toxicological relevance were, noted during daily observations or detailed weekly observations (weeks 1-3). During the functional observational battery (week 4), no clinical signs of toxicological relevance were noted. No test item-related differences in the mean fore- or hindlimb grip strength were noted at any dose level tested. No test item-related differences in the mean locomotor activity were noted at any dose level tested. The mean daily food consumption of the test item-treated rats was unaffected. The mean body weights of the test item-treated rats were unaffected.

No test item-related differences were noted in the hematology parameters after the treatment period and no late effects were seen after the recovery period.

When compared with the controls, elevated cholesterol and phospholipid levels were noted after the treatment period in males and females treated with 450 mg/kg/day. These differences also exceeded the respective ranges of the historical control data. Elevated phospholipids were also noted in females treated with 50 mg/kg/day and 150 mg/kg/day, but remained within the ranges of the historical control data. These differences were no longer evident after the recovery period. Triglycerides were elevated after the treatment and recovery periods in females treated with 450 mg/kg/day when compared with the controls. Although triglycerides were also elevated after the treatment and recovery periods in males at this dose level, all differences in triglycerides remained within the ranges of the historical control data. These differences were considered to be non-specific test item-related changes possibly related to metabolic adaptive changes in the liver.

No test item-related differences were noted in the urinalysis parameters after the treatment period and no late effects were seen after the recovery period.

Test item-related differences in organ weights after four weeks' treatment were restricted to increased liver weights in males and females treated with 150 mg/kg/day and 450 mg/kg/day. These differences were considered likely to have resulted from metabolic adaptation and were not considered to adverse changes. All other organ weights and ratios were considered to be unaffected.

Elevated mean absolute and relative liver weights persisted in test item-treated females after the recovery period, whereas the liver weights of males compared favorably with those of the control males. The differences noted in the females were considered to represent partial reversal insofar as hepatocellular hypertrophy was not seen microscopically after the recovery period.

There was no gross lesion that could be attributed to treatment with the test item.

Hepatocellular hypertrophy, mainly centrilobular at minor severity degrees, was noted in animals from both sexes at 150 and 450 mg/kg/day. There was no further indicator for findings in the liver that could be attributed to treatment with the test item. Moreover, the findings recovered completely after the recovery period. Therefore, this finding is considered to be not of adverse nature.

Conclusion

Test item-related findings noted after the treatment period included changes in clinical chemistry parameters associated with the liver (elevated cholesterol in both sexes at 450 mg/kg/day and elevated triglycerides in females at 450 mg/kg/day that reverted after recovery to levels comparable to the historical control values; elevated phospholipids in females at 50 and 150 mg/kg/day and both sexes at 450 mg/kg/day that remained within or reverted after recovery to levels comparable to the historical control values); increased liver weights in both sexes treated with 150 mg/kg/day and 450 mg/kg/day that showed complete reversal in males and partial reversal in females after the recovery period; and minor degrees of mainly centrilobular hepatocellular hypertrophy in animals from both sexes at 150 and 450 mg/kg/day that recovered completely after the recovery period.

Therefore, these findings were considered likely to be due to metabolic adaptation and were not adverse. Although NOEL could not be established, the NOAEL was considered to be 450 mg/kg/day.