(25S)-25-Cyclohexyl-5-O-demethyl-25-de(1-methylpropyl)-22,23-dihydroavermectin A1a

Acute Toxicity: oral

Administrative data

Endpoint:

acute toxicity: oral

Type of information:

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

Adequacy of study:

key study

Study period:

From 29 Oct to 12 Nov 1987

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study run to a method comparable with current guidelines and to GLP

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1988

Report date:

1988

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: Acute toxicology Standard Procedure

Deviations:

no

GLP compliance:

yes

Test type:

standard acute method

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

(2aE,4E,8E)-(5'S,6S,6'R,7S,11R,13S,15S,17aR,20R,20aR,20bS)-6'-Cyclohexyl-5',6,6',7,10,11,14,15,17a,20,20a,20b-dodecahydro-20,20b-dihydroxy-5',6,8,19-tetramethyl-17-oxospiro(11,15-methano-2H,13H,17H-furo(4,3,2-pq)(2,6)benzodioxacyclooctadecin-13,2'-(2H)pyran)-7-yl 2,6-dideoxy-4-O-(2,6-dideoxy-3-O-methyl-alpha-L-arabino-hexopyranosyl)-3-O-methyl-alpha-L-arabino-hexopyranoside

Cas Number:

117704-25-3

Molecular formula:

C50H74O14

IUPAC Name:

(2aE,4E,8E)-(5'S,6S,6'R,7S,11R,13S,15S,17aR,20R,20aR,20bS)-6'-Cyclohexyl-5',6,6',7,10,11,14,15,17a,20,20a,20b-dodecahydro-20,20b-dihydroxy-5',6,8,19-tetramethyl-17-oxospiro(11,15-methano-2H,13H,17H-furo(4,3,2-pq)(2,6)benzodioxacyclooctadecin-13,2'-(2H)pyran)-7-yl 2,6-dideoxy-4-O-(2,6-dideoxy-3-O-methyl-alpha-L-arabino-hexopyranosyl)-3-O-methyl-alpha-L-arabino-hexopyranoside

Constituent 2

Reference substance name:

Avermectin A(sub 1a), 25-cyclohexyl-5-O-demethyl-25-de(1-methylpropyl)-

IUPAC Name:

Avermectin A(sub 1a), 25-cyclohexyl-5-O-demethyl-25-de(1-methylpropyl)-

Test material form:

solid - liquid: suspension

Details on test material:

Batch No.: 15497-87-3
Purity: 95.3%

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories Inc., Wilmington MA
- Age at study initiation: Six-week old
- Weight at study initiation: 164.7 to 173.0 grams for male rats, 141.1 to 150.5 grams for female rats
- Fasting period before study: overnight (i.e. for approximately 17 to 18 hours )
- Housing: Polycarbonate shoe box-type cages, males or females given the same dose were housed together (three per cage). The cage floor was covered with hardwood chip bedding (Ab-sob-dri, Lab products). All test animals were transferred into a clean cage each day.
- Diet (e.g. ad libitum): Prolab RMH-3000 pelleted rodent diet (Agway) ad libitum
- Water (e.g. ad libitum): Drinking water was obtained from a municipal water source subject to regulation by the U.S. Environmental Protection Agency. Water was suplied ad libitum from bottles that were changed two times a week.

ENVIRONMENTAL CONDITIONS
- Temperature (°F): 70±2
- Humidity (%): 50±5
- Air changes (per hr): approximately 18 times per hour with air filtered through 80-90% efficiency filters and finally through HEPA filters.
- Photoperiod (hrs dark / hrs light): illuminated by fluorescent lighting 12 hours a day (7:00 am-7:00pm).

IN-LIFE DATES: From 29 Oct to 12 Nov 1987

Administration / exposure

Route of administration:

oral: unspecified

Vehicle:

other: 0.1% (w/v) aqueous methylcellulose solution

Details on oral exposure:

VEHICLE
- Concentration in vehicle: 10%
- Amount of vehicle (if gavage):
- Justification for choice of vehicle:
- Lot/batch no. (if required): R74386-0376
- Purity:

MAXIMUM DOSE VOLUME APPLIED:

DOSAGE PREPARATION (if unusual):

CLASS METHOD (if applicable)
- Rationale for the selection of the starting dose

Doses:

500, 1000 and 2000 mg/kg

No. of animals per sex per dose:

3

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: All rats were observed for clinical signs and mortality for 14 days after dosing. The individual body weights of the animals was obtained at least six times during the study, i.e. on the day of dosing (day 0) and on the day 1, 4, 7, 10, and prior to the sacrifice on day 14.
- Necropsy of survivors performed: Animals that died during the study and those that survived to sacrifice were necropsied for gross pathological changes.
- Other examinations performed: Changes were apparent on the gastric mucosa of one male rat given the low oral dose of 500 mg/kg. Therefore, the stomach of this animal was submitted to Pathology for microscopic evaluation. Following fixation in 10% neutral buffered formalin, the tissue was trimmed, embedded in paraffin, cut at 5 to 6 microns, and stained with hematoxylin and eosin.

Statistics:

None stated

Results and discussion

Effect levels

Effect levels 1

Sex:

female

Dose descriptor:

approximate LD50

Effect level:

500 - 1 000 mg/kg bw

Based on:

test mat.

Effect levels 2

Sex:

male

Dose descriptor:

approximate LD50

Effect level:

1 000 - 2 000 mg/kg bw

Based on:

test mat.

Mortality:

No mortality was produced by an oral dose of 500 mg/kg in animals of either sex or by a dose of 1000 mg/kg in males. Two of three females given 1000 mg/kg and all rats given the high dose of 2000 mg/kg died.

Clinical signs:

other: In animals given the low dose of 500 mg/kg, no clinical signs were noted on the day of dosing (day 0), and one rat of either sex was asymptomatic throught the 14-day observation period. Within about 5 to 7 hours of dosing, the activity of animals given 10

Gross pathology:

In the animals found dead on day 2 or day 3, the liver was dark, a yellowish material was apparent on the mucosa of the stomach near the pylorus, and portions of the small intestine were rendened and contained a yellow material. In the rats found dead on day 4 or 6, the lungs were reddened and mottled, the liver was dark, and the pancreas appeared white. The stomach contained a considerable amount of food, but the intestines were essentially empty. The kidneys were dark in situ and reddened throughout when cross-sectioned, the spleen was small, and a lack of body fat was noted.
At sacrifice on day 14, no gross pathological changes were apperent in any of the surviving rats with the exception of one low dose male which had been asyptomatic throught the study period. In this animal, white focal areas, measuring 1 to 2 mm in diameter, were visible on the aglandular portion the stomach when viewed in situ. When the stomach was excised and oppened, six raised areas, ranging in size from 1 to 8 mm in diameter, were apperent on the aglandular mucosa. At the three larger areas, there was a very narrow band of whitish, thichened, and rounded tissue at the perimeter of the rained edge. The center of these areas was depressed and often contained a small amount oof white material that was firmly adhered to the underlying mucosa. No gross changes were noted on the glandular portion of the stomach, and all other internal organs of this animal appeared essentially normal.

Other findings:

Microscopically, the raised white areas that were seen grossly on the mucosa of the aglandular stomach are keratinaceous cysts with associated mucosal dysplasia. These structures appear to be developmental defects rather than treatment-related lesions. The mucosal projections consist of submucosal, keratin-filled cysts opening to the interior of the stomach via small pores surrounded by narrow rims of glandular mucosa consisting of many pits lined by simple cilumnar epithelium and scattered goblet cells. These are overlain by mucus, keratin, and cell debris and in turn are surrounded by rims of thickly keratinized, stratified squamous epithelium that becomes less keratinized where it extends down onto the stalk of each projection.

Applicant's summary and conclusion

Interpretation of results:

Toxicity Category IV

Remarks:

Migrated information Criteria used for interpretation of results: EU

Conclusions:

The approximate acute oral median lethal dose (LD50) of the test item in the female rat was estimated to be in the range of 500 - 1000 mg/kg body weight, and the approximate LD50 for males was between 1000 and 2000 mg/kg bw.