Isobutyric anhydride

Repeated dose toxicity: oral

Administrative data

Endpoint:

sub-chronic toxicity: oral

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: comparable to guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1987

Report date:

1987

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 408 (Repeated Dose 90-Day Oral Toxicity Study in Rodents)

Deviations:

yes

Remarks:

; no special functional observations

Principles of method if other than guideline:

no guideline stated, but study design is comparable to the procedure of OECD test guideline 408 (Repeated dose 90-day Oral Toxicity in Rodents)

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

2-methylpropan-1-ol

EC Number:

201-148-0

EC Name:

2-methylpropan-1-ol

Cas Number:

78-83-1

IUPAC Name:

2-methylpropan-1-ol

Details on test material:

- Name of test material (as cited in study report): isobutyl alcohol, isobutanol
- Analytical purity: no data
- Impurities (identity and concentrations): no data
- Lot/batch No.: AM 307, purchased from American Scientific Products, Romulus, MI, USA
- Stability under test conditions: stable
- Storage condition of test material: no data

Test animals

Species:

rat

Strain:

Crj: CD(SD)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories Inc., Portage, MI, USA
- Age at study initiation: 22 - 23 days
- Weight at study initiation: 45-55 g
- Fasting period before study: no
- Housing: individually in wire-bottom cages
- Diet (e.g. ad libitum): Purina Certified Rodent Laboratory Chow No. 5002 (pellet)
- Water (e.g. ad libitum): filtered municipal water
- Acclimation period: 7days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 1
- Humidity (%): 43 ± 5
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12 /12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

water

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS: dissolution in water

DIET PREPARATION
- Rate of preparation of dosing solution (frequency): weekly

VEHICLE
- Justification for use and choice of vehicle (if other than water):
- Concentration in vehicle: as required by dose
- Amount of vehicle (if gavage): 10 ml/kg bw

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

GC analysis with a Varian 2100 GC with flame ionization detector connected to a Spectra Physics Model 4100 recording integrator.
Analysis of the test material was performed at week 1, 3, 8, 9, and 13. Measured concentrations were found to in acceptable accordance with nominal values.

Duration of treatment / exposure:

92 days

Frequency of treatment:

daily

Doses / concentrations

Remarks:

Doses / Concentrations:
100, 316, 1000 mg/kg/day
Basis:
actual ingested

No. of animals per sex per dose:

30 in total (10 for interim sacrifice)
In addition, one group of 10 animals per sex (group V) for baseline observation (sacrifice prior to initiation of dosing)

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: preceding rage finding toxicity study (TLR study #032-001)
- Rationale for animal assignment (if not random): random
- Rationale for selecting satellite groups: no satellite groups

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily

DETAILED CLINICAL OBSERVATIONS: No data
- Time schedule:

BODY WEIGHT: Yes
- Time schedule for examinations: weekly

FOOD CONSUMPTION: Yes
- Time schedule for examinations: weekly

FOOD EFFICIENCY: No

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: during pretreatment period and at week 13
- Dose groups that were examined: all rats were examined

HAEMATOLOGY: Yes
- Time schedule for collection of blood: prior to initiation of dosing, at week 4 or 5, and at week 13 or 14
- Anaesthetic used for blood collection: Yes, CO2
- Animals fasted: No data
- How many animals: prior to dosing 10 animals per sex ( group V), at week 4 or 5 (interim sacrifice) and at week 13 or 14 (final sacrifice) 10 animals per sex from each group
- Parameters examined: hemoglobin (HGB), hematocrit (PCV), erythrocyte count (RBC), mean cell volume (MCV), mean cell hemoglobin (MCH), mean cell hemoglobin concentration (MCHC), total and differential leucocyte counts (WBC), estimated platelet count (PLT)

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: prior to initiation of dosing, at week 4 or 5, and at week 13 or 14
- Anaesthetic used for blood collection: Yes, CO2
- Animals fasted: No data
- How many animals: prior to dosing 10 animals per sex ( group V), at week 4 or 5 (interim sacrifice) and at week 13 or 14 (final sacrifice) 10 animals per sex from each group
- Parameters examined: alkaline phosphatase (Alk phos), blood urea nitrogen (BUN), glutamate pyruvate transaminase (SGPT), glutamate oxaloacetate transaminase (SGOT), glucose (Gluc), total protein (TP), albumin (Alb), A/G ratio (calculated), globulin (calculated), total bilirubin (Tot. bili.), sodium (Na), potassium (K), chloride (Cl), calcium (Ca), creatinine, inorganic phosphate (phos.), total carbon dioxide (TCO2), total serum cholesterol (Chol)

URINALYSIS: Yes
- Time schedule for collection of urine: prior to initiation of dosing, at week 4 or 5, and at week 13 or 14
- Metabolism cages used for collection of urine: Yes
- Animals fasted: No data
- Parameters examined. pH, specific gravity, glucose, protein, ketones, bilirubin, urobilinogen, microscopy of sediment.

NEUROBEHAVIOURAL EXAMINATION: No special examinations

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

Statistics:

body weight, food consumption, clinicopathologic, and organ weight data were tested for homogeneity of variance by Bartlett's method (Steel and Torrie, 1980).
If the data were found to be homogeneous, differences between control and treatment means were tested for statistical significance by the method of Dunnett (Dunnett, 1964).
If the data were found not to be homogeneous, the method of Gill (modified Dunnett's) was employed (Gill, 1977)

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

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:

no effects observed

Haematological findings:

no effects observed

Clinical biochemistry findings:

effects observed, treatment-related

Urinalysis findings:

no effects observed

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:

no effects observed

Histopathological findings: neoplastic:

not examined

Details on results:

CLINICAL SIGNS AND MORTALITY
Treatment related clinical signs were restricted to the high-dose group and included hypoactivity, ataxia, and salivation. Hypoactivity decreased in the course of the experiment and was only sporadically observed after week 4.
The mortality rate was 1/60, 1/60, 2/60 and 11/60 for the control, 100, 316, and 1000 mg/kg/day dose group, respectively. In combination with the results of the gross necropsy and histologic findings, the increased number of death in the high-dose group are not related to a systemic toxicity of orally administered isobutyl alcohol.

BODY WEIGHT AND WEIGHT GAIN
During week 1 the males of the 1000 mg/kg/day dose group gained 10% less body weight than the controls.

FOOD CONSUMPTION
For the first two weeks of the study, food consumption averages of the 1000 mg/kg day dose group males and females were significantly lower than controls ( p ≤ 0.01 - males, p ≤ 0.05 - females week 1 and p ≤ 0.01 - males/females week 2).

FOOD EFFICIENCY
no examined

WATER CONSUMPTION
not examined

OPHTHALMOSCOPIC EXAMINATION
no effects

HAEMATOLOGY
no effects

CLINICAL CHEMISTRY
There was no definite treatment related effect on clinical pathologic parameters. However, the possibility of treatment-related effects was suggested by differences between control and treatment group mean serum potassium, albumin, and total protein concentrations. Group mean serum potassium concentration for males and females in the 1000 mg/kg/day group was 11-15% lower than the control group means at the interim evaluation, but it was similar for treated and control groups at the final clinical pathologic evaluation. Slightly lower than control group means for femals of the 316 mg/kg/day dose group (7%, p ≤ 0.05)and for females of the 1000 mg/kg/day dose group (9% p ≤ 0.01) appeare to be a result of higher than expected values in the control group rather than abnormally low values in the treated groups.

URINALYSIS
no effects

NEUROBEHAVIOUR
not examined

ORGAN WEIGHTS
no effects

GROSS PATHOLOGY
no effects

HISTOPATHOLOGY: NON-NEOPLASTIC
no effects

HISTOPATHOLOGY: NEOPLASTIC (if applicable)
not examined

HISTORICAL CONTROL DATA (if applicable)

Effect levels

Dose descriptor:

NOEL

Effect level:

316 mg/kg bw/day (actual dose received)

Sex:

male/female

Basis for effect level:

other: overall effects clinical signs; body weight; food consumption; clinical chemistry

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Four rats were determined to have died from perforation of the esophagus (incurred during dosing). The case of death of another ten rats was acute tracheitis (or bronchial hemmorhage), which was apparently due to the regurgitation and subsequent aspiration of the isobutyl alcohol and/or its vapors into the trachea (and probably the nasal cavity). The acute lesions of the trachea (inflammation and/or necrosis) seen histologically support this theory.

Applicant's summary and conclusion

Executive summary:

In a subchronic toxicity study (90 days) isobutanol (purity not stated) was administered to 30 rats/sex/dose by gavage at dose levels of 0, 100, 316, and 1000 mg/kg bw/day on the basis of a priliminary range finding study.

 

Treatment related effects were seen only at a dose level of 1000 mg/kg bw/day, but not at dose levels of 100 or 316 mg/kg bw/day. At the 1000 mg/kg bw/day dose level, hypoactivity was observed in all rats and body weight gain in the males was 18% below the control average during week 1. Food consumption averages were below those of the controls for both males and females during week 1 and 2. In addition, serum potassium averages (both sexes) were 11-15% below control averages at the interim evaluation (day 29) only and this may have been related to treatment.

No difference between dosed groups and controls were found for ophthalmoscopic examination, haematology, urinalysis, organ weights, gross pathology and histopathology.

The NOEL is 316 mg/kg bw/day for males and females (EPA/Res. Triangle Inst. 1987)

This subchronic toxicity study in the rat is acceptable and satisfies the guideline requirements for a subchroic oral study (OECD 408).