Registration Dossier

Administrative data

Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
18 November - 2 December 1991
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: No deviations reported. The study fully meets the reported guidelines.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1992
Report date:
1992

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
other: EPA (40 CFR Part 792)
Deviations:
no
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Santovar A
- Substance type: white powder
- Physical state: solid
- Analytical purity: 98%
- Impurities (identity and concentrations): not mentioned
- Lot/batch No.: NOA027
- Expiration date of the lot/batch: 06-1992
- Stability under test conditions: yes, verified
- Storage condition of test material: room temperature
- Other: stability, homogeneity and dose of the tested substance are verified

Test animals

Species:
rat
Strain:
Sprague-Dawley
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories, Inc.
- Age at study initiation: females - 12 weeks
- Weight at study initiation: females - 227 - 276g
- Fasting period before study: not mentioned
- Housing: individually in stainless steel cages
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 11 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18 -26
- Humidity (%): 40 - 70
- Air changes (per hr): not mentioned
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
corn oil
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: prepared once weekly, daily aliquots were stored refrigerated.

Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Prestudy analytical chemistry evaluations indicated that Santovar A was homogeneous and stable in corn oil for up to eight days when stored refrigerated. Analysis of dosing preparations resulted in average test article recoveries ranging from 99.2 to 103.0% indicating that the mixtures were accurately prepared.
Details on mating procedure:
No details mentioned.
Duration of treatment / exposure:
From gestation day 6 - 15.
Frequency of treatment:
Once daily
Duration of test:
Until gestation day 20
Doses / concentrations
Remarks:
Doses / Concentrations:
0, 20, 70, 175 mg/kg/day
Basis:
actual ingested
No. of animals per sex per dose:
25 females
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: based on range finding study (3044.226)

Examinations

Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: twice daily and one half and two hours after dosing

BODY WEIGHT: Yes
- Time schedule for examinations: 0, 6, 9, 12, 16, and 20 days.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 20
- Organs examined: thoracic, abdominal and pelvic cavities. Uterus in detail
Ovaries and uterine content:
The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
Fetal examinations:
- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: half per litter
- Skeletal examinations: Yes: half per litter
- Head examinations: No
Statistics:
Continuous maternal and fetal data, including body weights, body weight gain, food consumption, number of fetuses, implantation sites and corpora lutea, were analyzed by one-way analysis of variance (ANOVA) followed by Dunnett's test. The Mann-Whitney U test was used to compare post-implantation loss and resorptions. Fetal sex ratios were analyzed using the Chi-Square test. Fisher's Exact test was used to analyze the incidence and number of fetal malformations and variations utilzing the dam (litter) as the experimental unit. All analyses were two-tailed with a minimum signifcance level of 5%.

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
The toxicity was characterized by an increase in the incidence of reddish colored vaginal discharge and post-dose salivation at the 70.0 mg/kg/day.
Dermal irritation (if dermal study):
not examined
Mortality:
no mortality observed
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
not specified
Clinical biochemistry findings:
not specified
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Immunological findings:
not examined
Organ weight findings including organ / body weight ratios:
not specified
Gross pathological findings:
not specified
Neuropathological findings:
not examined
Histopathological findings: non-neoplastic:
not examined
Histopathological findings: neoplastic:
not examined
Other effects:
not specified

Maternal developmental toxicity

Number of abortions:
not specified
Pre- and post-implantation loss:
not specified
Total litter losses by resorption:
not specified
Early or late resorptions:
not specified
Dead fetuses:
not specified
Changes in pregnancy duration:
not specified
Changes in number of pregnant:
not specified
Other effects:
not specified
Details on maternal toxic effects:
Maternal toxic effects:yes
Details on maternal toxic effects:
Oral administration of Santovar A produced slight maternal toxicity at the 70.0 mg/kg/ day level and substantial maternal toxicity at the 175.0 mg/kg/day level. The toxicity was characterized by an increase in the incidence of reddish colored vaginal discharge and post-dose salivation at the 70.0 mg/kg/day level and more frequent and severe clinical signs, body weight loss and reduced food consumption at the 175.0 mg/kg/day level.

Effect levels (maternal animals)

open allclose all
Key result
Dose descriptor:
NOEL
Effect level:
20 mg/kg bw/day (actual dose received)
Basis for effect level:
other: maternal toxicity
Key result
Dose descriptor:
NOAEL
Effect level:
70 mg/kg bw/day (actual dose received)
Basis for effect level:
other: maternal toxicity
Key result
Dose descriptor:
NOEL
Effect level:
70 mg/kg bw/day (actual dose received)
Basis for effect level:
other: developmental toxicity

Maternal abnormalities

Key result
Abnormalities:
effects observed, treatment-related
Localisation:
vagina

Results (fetuses)

Fetal body weight changes:
effects observed, treatment-related
Description (incidence and severity):
Mean fetal body weight was slightly, but statistically reduced at the 175.0 mg/kg/day level when compared to the control group.
Reduction in number of live offspring:
not specified
Changes in sex ratio:
not specified
Changes in litter size and weights:
not specified
Changes in postnatal survival:
not specified
External malformations:
not specified
Skeletal malformations:
effects observed, non-treatment-related
Description (incidence and severity):
Slight, nonstatistical increases in the incidence of skull anomalies and 7th cervical ribs were observed in the 175.0 mg/kg/day group.
Visceral malformations:
not specified
Other effects:
not specified
Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:yes
Details on embryotoxic / teratogenic effects:
Mean fetal body weight was slightly, but statistically reduced at the 175.0 mg/kg/day level when compared to the control group. Slight, nonstatistical increases in the incidence of skull anomalies and 7th cervical ribs were observed in the 175.0 mg/kg/day group.

Effect levels (fetuses)

Key result
Dose descriptor:
NOEL
Effect level:
70 mg/kg bw/day (nominal)
Based on:
test mat.
Sex:
not specified
Basis for effect level:
fetal/pup body weight changes

Fetal abnormalities

Key result
Abnormalities:
not specified

Overall developmental toxicity

Key result
Developmental effects observed:
not specified
Lowest effective dose / conc.:
20 mg/kg bw/day
Treatment related:
yes

Any other information on results incl. tables

The increase in reddish colored vaginal discharge did not result in adverse effects in rats (e.g. no change in spontanious abortions, in litter size etc). Post-dose salivation is not considered adverse. Therefore the reviewer considers 70 mg/kg bw/day as a NOAEL.

Applicant's summary and conclusion

Conclusions:
Sprague-Dawley rats were treated with 0, 20, 70, and 175 mg/kg 2,5-Di-t-pentylhydroquinone once daily during gestation days 6-15. Based on the results of this study, a dosage level of 20.0 mg/kg/day was considered a no-observed-effect level (NOEL) for maternal toxicity and a dosage level of 70.0 mg/kg/day was considered a NOEL for developmental toxicity. Santovar A at a dosage level of 175.0 mg/kg/day produced substantial maternal toxicity with minimal developmental toxicity.
Executive summary:

This study was performed to detect and evaluate the potential embryotoxic or teratogenic effects of Santovar A when administered orally to pregnant rats during the period of major organogenesis. The study design consisted of a vehicle control and three treatment groups. Each group contained twenty-five mated female Sprague-Dawley rats. The test article was mixed with corn oil and administered at dosage levels of 20.0, 70.0 and 175.0 mg/kg/day from gestation day 6 through gestation day 15. All doses were given at a constant volume of 5 ml/kg. Control animals were administered corn oil under the same experimental conditions and at an equivalent dose volume. The animals were observed daily for clinical signs of toxicity. Body weights and food consumption were measured on gestation days 0, 6, 9, 12, 16 and 20. All females were euthanized on gestation day 20 and subjected to cesarean section. Fetuses were individually weighed, sexed and examined for external, visceral and skeletal abnormalities.

 

Oral administration of Santovar A produced slight maternal toxicity at the 70.0 mg/kg/day level and substantial maternal toxicity at the 175.0 mg/kg/ day level.

The toxicity was characterized by an increase in the incidence of reddish colored vaginal discharge and post-dose salivation at the 70.0 mg/kg/day level and more frequent and severe clinical signs, body weight loss and reduced food consumption at the 175.0 mg/kg/day level. No adverse clinical signs were observed in the 20.0 mg/kg/day group. Similarly, no treatment-related differences in mean body weights, body weight gain or food consumption were observed at the 20.0 or 70.0 mg/kg/day levels. Mean fetal body weight was slightly, but statistically reduced at the 175.0 mg/kg/day level when compared to the control group. All other cesarean section parameters were comparable among the groups. No apparent treatment-related malformations or developmental variations were observed at the 20.0 or 70.0 mg/kg/day levels. Slight, non-statistical increases in the incidence of skull anomalies and 7th cervical ribs were observed in the 175.0 mg/kg/day group. The number of litters with sternebra(e) #5 and/or #6 unossifed was also statistically increased at this level when compared to the control group. The number of litters in the control group with unossifed sternebrae in this study is unusually low when compared to SLS historical control data.

Therefore, it is not clear if the increase in the number of litters with sternebra(e) #5 and/or #6 unossified at the 175.0 mg/kg/day level in this study was spontaneous or associated with the reduced fetal body weights observed at this level.

 

Based on the results of this study, a dosage level of 20.0 mg/kg/day was considered a no-observed-effect level (NOEL) for maternal toxicity and a dosage level of 70.0 mg/kg/day was considered a NOEL for developmental toxicity.

Santovar A at a dosage level of 175.0 mg/kg/day produced substantial maternal toxicity with minimal developmental toxicity.