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Toxicological information

Developmental toxicity / teratogenicity

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Administrative data

Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1997
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Well documented, according to accepted guidelines.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1997
Report Date:
1997

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
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): hexylene glycol
- Physical state: liquid
- Lot No.: 1
- Analytical purity: 99.72%
- Storage condition of test material: in a sealed container at room temperature in the dark

Test animals

Species:
rat
Strain:
other: Crl:CD(SD)BR
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River (UK) Ltd. Margate
- Age at study initiation: 9 weeks
- Weight at study initiation: between 188.8 to 256.5 g
- Fasting period before study: None
- Housing: in groups of 4 in stainless steel wire mesh cages suspended over cardboard-lined trays.
- Diet (e.g. ad libitum): SQC Rat and Mouse Breeder Diet No 3, Expanded, Special Diets Services Ltd, Witham was provided ad libitum
- Water (e.g. ad libitum): Mains drinking water was available ad libitum
- Acclimation period: None


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19 to 25
- Humidity (%): 40 to 70
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light): 12/12


Administration / exposure

Route of administration:
oral: gavage
Vehicle:
water
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: solutions of the test article in the vehicle were prepared daily for each group. The test article was weighed into a beaker, some vehicle was added and the mixture was stirred until homogenous. It was transferred to a measuring cylinder and made up to final volume. The formulation was transferred to a bottle and stirred again until homogeneous. Before dosing the formulations were stored at room temperature in sealed containers.

Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Analyses for achieved concentrations were conducted on samples of the dosing formulations perpared for each group on Days 1 and 17 of the dosing period. In addition, analyses were preformed on samples from group 2 on day 8. The reserve samples of the formulations for groups 3 and 4 on day 17 and additional formulations for groups 3 and 4 were prepared after the end of dosing.
Details on mating procedure:
Mating was conducted at the suppliers laboratory. It was confirmed by the presence of a vaginal plug or sperm in a vaginal smear. The day on which mating was observed was designated as Day 0 of gestation and females were delivered to the laboratory by Day 3 of gestation.
Duration of treatment / exposure:
10 days (day 6 to day 15 of gestation)
Frequency of treatment:
daily
Duration of test:
17 days (day 3 to day 20 of gestation)
No. of animals per sex per dose:
24 females/dose group
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: selected by sponser following review of results of a 14-day toxicity study in rats
- Rationale for animal assignment (if not random): random

Examinations

Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily
- Cage side observations; mortality

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: daily

BODY WEIGHT: Yes
- Time schedule for examinations: on days 4, 6, 7, 8, 9, 12, 15, 17 and 20 of gestation

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: No data

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

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 20
- Organs examined: liver, kidney, adrenals, and spleen


Ovaries and uterine content:
The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: No
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Other: pregnancy status
Fetal examinations:
- External examinations: Yes: [all per litter]
- Soft tissue examinations: Yes: [half per litter]
- Skeletal examinations: Yes: [half per litter]
- Head examinations: Yes: [half per litter]

- Individual foetal weights were recorded, and foetal abnormalities were recorded
Statistics:
Data were processed where appropriate, to give litter mean values, group mean values, and standard deviations. For each parameter analysed, one of 3 procedures was used;

1. ANOVA. Pairwise comparisons were made using Dunnet's test. Post-dose regression test was performed to determine whether there was a linear relationship between increasing dose and response. Levene's test for equality of variances was also performed.

2. Kruskal-Wallis ANOVA, the Terpstra-Jonckheere test for a dose related trend and the Wilcoxon rank sum test for pairwise comparisons.

3. Cochran-Armitage test for dose response and the Fisher-Irwin Exact test for pairwise comparisons were performed. Where no significant dose response test was seen a Bonferroni adjustment was applied to the pairwise comparisions.
Indices:
Not reported
Historical control data:
Not reported

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:
Maternal toxic effects:yes

Details on maternal toxic effects:
The majority of rats in the high dose group lost weight over the first day of dosing so that the mean body weight gain was significantly lower than controls between days 6 and 7 of gestation. After day 7 of gestation, group mean weight gain was similar to control animals. Group mean intake of the high dose animals was significantly lower than controls between days 6 to 8 of gestation. At necropsy, there were minor incidences of large pale livers, which were not considered to be an adverse effect of treatment because this is a common finding in this strain of rat. The pregnancy rate was 91.7 to 95.8% for all groups.

Effect levels (maternal animals)

Key result
Dose descriptor:
NOAEL
Effect level:
300 mg/kg bw/day (actual dose received)
Based on:
test mat.
Basis for effect level:
body weight and weight gain

Results (fetuses)

Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
The mean number of corpora lutea in the high dose group was slightly higher and the mean number of implantations was slightly lower than the control values. This resulted in a significant increase in percentage pre-implantation loss. There was a slight, non-significant reduction in mean litter weight in the high dose group compared to control. Malformations were observed in all dose groups. The nature and incidence was unrelated to maternal treatment. The overall incidence of external/visceral variations was slightly higher in the treated groups compared to the control due to a higher proportion of foetuses showing subcutaneous hemorrhage of the trunk and limbs. The overall incidence of skeletal variations in the treated groups was also slightly higher than control; which were incomplete ossification of cranial, sternebral, or forepaw structures.

Effect levels (fetuses)

Key result
Dose descriptor:
NOAEL
Effect level:
300 mg/kg bw/day (actual dose received)
Based on:
test mat.
Basis for effect level:
other: slight delay in ossification, greater number of fetuses with extra thoraco-lumbar ribs, and slight decrease (not statistically significant) in foetal body weight at 1000 mg/kg bw/d. No teratogenic effects were observed.

Fetal abnormalities

Abnormalities:
not specified

Overall developmental toxicity

Developmental effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
Oral administration of 1000 mg/kg body weight/day of hexylene glycol to pregnant female rats was associated with slightly reduced body weight gain and food intake. At 300 mg/kg body weight/day of hexylene glycol, there was a transient reduction in body weight gain and only at 30 mg/kg body weight/day of hexylene glycol there were no adverse effects. At 1000 mg/kg body weight/day of hexylene glycol, marginally lower foetal weights and marginally higher incidences of foetal variations were associated with the reduction in maternal weight gain. There were no adverse effects of treatment on pregnancy or the foetus at 30 or 300 mg/kg body weight/day.
Executive summary:

The developmental toxicity of hexylene glycol has been assessed in a GLP study in rats that was conducted according to OECD test guideline 414 (date not provided) (Clode, 1997). Hexylene glycol was administered by oral gavage to groups of pregnant female rats (Crl:CD(SD)BR strain) on gestation days 6 to 15, inclusive. Dose levels were 0 (water vehicle), 30, 300, or 1000 mg/kg body weight/day and 24 pregnant females were included in each dosing group. Animals were killed on gestation day 20 and uterine/implantation and foetal effects were examined.

Hexylene glycol did not affect survival, clinical observations, or necropsy findings in maternal animals. Body weight gain was decreased over the first dosing period (gestation days 6 to 7) in mid- and high-dose maternal animals and returned to control levels thereafter. Food intake was lower in high-dose maternal animals over the gestation day 6 to 7 and 7 to 8 periods and returned to control levels thereafter. No other effects were observed in the maternal animals of any dose group. Mean litter and foetal weights in the high-dose group were marginally but not statistically significantly lower than in the control group. There were no adverse effects of treatment on sex ratio or on the incidences of foetal malformations or external/visceral variations. The incidence of skeletal variations in the high-dose group was slightly higher than in the control group but the nature of the specific changes involved (mainly incomplete ossification of cranial, sternebral, or forepaw structures) suggested only marginal delay in the normal ossification process. Moreover, the variations in the high-dose group were considered to be associated with the reduction in maternal body weight gain. Based on these findings a NOAEL of 300 mg/kg body weight/day was determined for maternal and foetal effects of hexylene glycol (Clode, 1997).