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Toxicological information

Repeated dose toxicity: dermal

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Administrative data

Endpoint:
sub-chronic toxicity: dermal
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study performed to GLP and guideline

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1994
Report Date:
1994

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
EPA OPP 82-3 (Subchronic Dermal Toxicity 90 Days)
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): 5,5-dimethylhydantoin (DMH)
-Physical state: white crystalline powder
-Analytical purity: >99.8%
-Lot/batch No.: NO432543
-Stability under test conditions: Stability analysis indicated that DMH remained stable in water for at least 14 days when stored at room temperature.

Test animals

Species:
rat
Strain:
other: CD
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories (Portage, MI)
- Age at study initiation: 32 days old
- Weight at study initiation: Males: 236-313 g - Females: 159-215 g
- Housing: stainless steel cages (1 animal per cage during study)
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: 3 weeks

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 66-77 °F
- Humidity (%): 40-70%
- Air changes (per hr): 10 room air changes per hour.
- Photoperiod: 12 hours per day of fluorescent light.

Administration / exposure

Type of coverage:
occlusive
Vehicle:
water
Details on exposure:
TEST SITE
- Area of exposure: Dosing solution was applied directly to the back
- Type of wrap if used: Wrapped with VETRAP® Bandaging Tape (3M Personal Care Products) and secured with Elastikon®
- Time intervals for shavings or clipplings: Ten days prior to initiation of study


REMOVAL OF TEST SUBSTANCE
- Washing (if done): Rinsed with water
- Time after start of exposure: After 6 hours


TEST MATERIAL
- Amount applied: 0, 39,130 and 390 mg/kg/day corresponding to a dose volume 3.0, 0.3, 1.0 and 3.0 mL/kg/day.
- Constant volume or concentration used: yes - a constant concentration of 13% (w/w) DMH was used.

Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Concentration verification analyses on solutions used for dosing showed analytical values ranging from 99.2% to 106.3% of nominal for the 6 periods of analysis.
Duration of treatment / exposure:
90 days
Frequency of treatment:
6 hours/day; 5 days per week
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
39
Basis:
nominal per unit body weight
Remarks:
Doses / Concentrations:
130
Basis:
nominal per unit body weight
Remarks:
Doses / Concentrations:
390
Basis:
nominal per unit body weight
No. of animals per sex per dose:
15/sex/group
Control animals:
yes
Details on study design:
- Dose selection rationale: Previously a 5-day repeated dermal toxicity study was conducted with DMH to generate information to aid in the selection of dose levels for the 90 day study. Male rats were treated dermally 6 hours/day (occluded) for 5 days with 2 mL/kg of 5 or 10% aqueous solutions of DMH or 25 or 50% aqueous mixtures of DMH. These treatments corresponded to dose levels ranging from 100 to 1000 mg/kg/day. No toxicity or skin irritation was observed. Results of the dose solution preparation indicated that even mixtures of DMH in water could not be prepared above saturating DMH concentrations (~13%).

DMH dose levels for the 90 day study were selected based on the results of the preliminary 5 day study, the maximum aqueous solubility of DMH (13%) and the maximum dose volume which could be adminsitered in the test system (3.0 mL/kg/day).

Examinations

Observations and examinations performed and frequency:

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: twice daily

DERMAL IRRITATION (if dermal study): Yes

BODY WEIGHT: Yes
- Time schedule for examinations: weekly

FOOD CONSUMPTION: Yes
- Time schedule for examinations: weekly

WATER CONSUMPTION: No

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: prior to first exposure and following sixty-third treatment

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at end of study
- How many animals: all animals
- Parameters: Haematocrit, haemoglobin, erythrocyte count, total and differential leukocyte count, platelet count, reticulcyte count, mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC).

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at end of study
- How many animals: all animals
- Parameters examined: sodium, potassium, chloride, calcium, phosphorus, glucose, cholesterol, urea nitrogen, total bilirubin, direct bilirubin, indirect bilirubin, creatinine, total protein, albumin, globulin, A/G ratio, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, gamma glutamyl transpeptidase.

URINALYSIS: No
Sacrifice and pathology:
GROSS PATHOLOGY AND HISTOPATHOLOGY: Yes
High dose group and controls
organs: brain, spinal cord, pituitary, thyroid, parathyroid, thymic region, oesophagus, salivary glands, stomach, small and large intestines, liver, pancreas, kidneys, adrenals, spleen, heart, trachea, lungs, aorta, uterus, vagina, female mammary gland, prostate, testes, seminal vesicles, urinary bladder, lymph nodes sciatic nerve, femur, sternum (including marrow), eyes, exorbital lacrimal gland, thigh musculature, skin (treated and untreated)
* Lungs, liver, kidneys, treated and untreated skin were examined from the low and mid-dose groups. In addition, submandibular lymph nodes were examined from all low and mid dose male rats
Other examinations:
Not specified
Statistics:
Data for quantitative continuous variables were compared for the 3 treatment groups and control group by use of Levene’s test for equality of variances, analysis of variance (ANOVA), and t-tests. The t-tests were used when the F value from the ANOVA was significant. When Levene’s test indicated homogenous variances, and the ANOVA was significant, a pooled t-test was used for pairwise comparisons. When Levene’s test indicated heterogenous variances all groups were compared by an ANOVA for unequal variances followed, when necessary, by a separate variance t-test for pairwise comparisons. Nonparametric data were statistically evaluated using the Kruskal-Wallis test followed by the Mann-Whitney U test when appropriate. Incidence data were compared using Fishers exact test. For all statistical tests, the probability value of <0.05 (two-tailed) was used as the critical level of significance.

Results and discussion

Results of examinations

Clinical signs:
no effects observed
Dermal irritation:
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:
not examined
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
no effects observed
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
not examined
Details on results:
CLINICAL SIGNS
No treatment effects.

MORTALITY One male from the control group was found dead on day 17 and one male from the low dose group was sacrificed moribund on day 39.

BODY WEIGHT GAIN
No treatment related effects.

FOOD CONSUMPTION
No treatment related effects.

OPHTHALMOSCOPIC EXAMINATION
No adverse effects.

HAEMATOLOGY
No treatment related effects.

CLINICAL CHEMISTRY
No treatment related effects

ORGAN WEIGHTS
No treatment related effects

GROSS PATHOLOGY
No treatment related effects.

HISTOPATHOLOGY: NON-NEOPLASTIC
No treatment related effects.

Effect levels

Dose descriptor:
NOEL
Effect level:
390 mg/kg bw/day (nominal)
Sex:
male/female
Basis for effect level:
other: Based upon the observation of no clinical signs of toxicity or effects on any study parameters.

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
No clinical signs of toxicity or effects on any of these parameters were found. Based on the results of this study, repeated dermal exposure to saturated aqueous solutions of DMH does not result in systemic toxicity or skin irritation in the rat. NOEL = 390 mg/kg bw/d.