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Diss Factsheets

Administrative data

Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1 September - 26 September 1987.
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1987
Report date:
1987

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 406 (Skin Sensitisation)
GLP compliance:
yes
Type of study:
guinea pig maximisation test
Justification for non-LLNA method:
The study was performed in 1990 before the LLNA method had been validated.

Test material

Constituent 1
Chemical structure
Reference substance name:
1,3-dihydro-5-methoxy-2H-benzimidazole-2-thione
EC Number:
253-326-2
EC Name:
1,3-dihydro-5-methoxy-2H-benzimidazole-2-thione
Cas Number:
37052-78-1
Molecular formula:
C8H8N2OS
IUPAC Name:
5-methoxy-1,3-dihydro-2H-benzimidazole-2-thione
Specific details on test material used for the study:
Batch no. : 685 20-01.
Purity: 99.2%.

In vivo test system

Test animals

Species:
guinea pig
Strain:
Dunkin-Hartley
Sex:
female
Details on test animals and environmental conditions:
The guinea-pigs selected for the study were all acclimated to the laboratory environment.
Mean weight: 426 grams

The guinea-pigs were housed in suspended cages with wire mesh floors . They had free access to tap water and a Vitamin C-enriched Guinea-Pig Diet. Hay was given once weekly.
Animal room temperature was approximately 21°C and relative humidity 30-70%.
Air exchange was maintained at approximately 15 air changes per hour and lighting was controlled by means of a time switch to give 12 hours of artificial light in each 24 hour period.

Study design: in vivo (non-LLNA)

Inductionopen allclose all
Route:
intradermal
Vehicle:
other: liquid paraffin
Concentration / amount:
Injection 1: 0,1 ml FCA in water,
Injection 2: 0,1 ml Metmercazole 5 w/w% in liquid paraffin
Injection 3: 0,1 ml, Metmercazole 5% wjw in a 50 : 50 mixture of Freund's
complete adjuvant and liquid paraffin.
Route:
epicutaneous, occlusive
Vehicle:
other: Liquid paraffin
Concentration / amount:
50 w/w%
Day(s)/duration:
A week after the injections; application 48 hours
Challenge
Route:
epicutaneous, open
Vehicle:
other: liquid paraffin
Concentration / amount:
25 och 50 w/w%
Day(s)/duration:
24 hours
No. of animals per dose:
20
20 control animals
Details on study design:
Induction: 20 animals were given 3 injections:1. Freund's complete adjuvant was diluted with anequal volume of water for irrigation, 2. Metmercazole, 5% wjw in liquid paraffin, 3 . Metmercazole, 5% wjw in a 50 : 50 mixture of Freund's complete adjuvant and liquid paraffin.

Topical appl ication (induction phase): One week after the injections :2 x 4 cm patch of Whatman No. 3 paper was saturated with Metmercazole, 50% w/w in liquid paraffin. The patch was
placed on the skin and covered by a length of impermeable plastic adhesive tape. The dressing was left in place for 48 hours.

Control animals: During the induction period the control animals were treated similarly to the test animals with the exception that the test compound was omitted from the intradermal injections and topical application.

Challange: The test and control animals were challenged topically two weeks after the induction period using Metmercazole, 50% and 25% w;w in liquid paraffin.

The challenge sites were evaluated 24, 48 and 72 hours after removal of the patches.

Results and discussion

In vivo (non-LLNA)

Resultsopen allclose all
Reading:
1st reading
Hours after challenge:
24
Group:
test chemical
Dose level:
25 w/w% and 50 w/w%
No. with + reactions:
19
Total no. in group:
20
Remarks on result:
positive indication of skin sensitisation
Reading:
2nd reading
Hours after challenge:
48
Group:
test chemical
Dose level:
25 w/w% and 50 w/w%
No. with + reactions:
19
Total no. in group:
20
Remarks on result:
positive indication of skin sensitisation
Reading:
other: 3rd reading
Hours after challenge:
72
Group:
test chemical
Dose level:
25 w/w% and 50 w/w%
No. with + reactions:
19
Total no. in group:
20
Remarks on result:
positive indication of skin sensitisation
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
25 w/w% and 50 w/w%
No. with + reactions:
0
Total no. in group:
20
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
25 w/w% and 50 w/w%
No. with + reactions:
0
Total no. in group:
20
Reading:
other: 3rd reading
Hours after challenge:
72
Group:
negative control
Dose level:
25 w/w% and 50 w/w%
No. with + reactions:
0
Total no. in group:
20

Applicant's summary and conclusion

Interpretation of results:
Category 1 (skin sensitising) based on GHS criteria
Conclusions:
In this screening test, performed in twenty albino guinea-pigs, Metmercazole produced evidence of delayed contact hypersensitivity in nineteen animals. The material is a skin sensitiser according to this test.