N-tert-butylbenzothiazole-2-sulphenamide

Repeated dose toxicity: dermal

Administrative data

Endpoint:

short-term repeated dose toxicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

TG compliant study undertaken to GLP.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1981

Report date:

1981

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 410 (Repeated Dose Dermal Toxicity: 21/28-Day Study)

Deviations:

yes

Remarks:

animals tested: one-half with intact skin, one-half with abraded skin

Principles of method if other than guideline:

Santocure NS (N-tert-butylbenzothiazole-2-sulphenamide) was administered by dermal application to 3 groups of 10 male and 10 female rabbits, one-half with intact skin and one-half with abraded skin, five days per week for 3 consecutive weeks at dose levels of 125, 500 or 2000 mg/kg. An identical control group was treated with saline. Criteria evaluated for treatment effect included mortality, pharmacotoxic signs, body weights, dermal irritation, hematological and clinical biochemical determinations, organ weights and macroscopic and selected microscopic evaluation of tissue.

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

N-tert-butylbenzothiazole-2-sulphenamide

EC Number:

202-409-1

EC Name:

N-tert-butylbenzothiazole-2-sulphenamide

Cas Number:

95-31-8

Molecular formula:

C11H14N2S2

IUPAC Name:

N-(1,3-benzothiazol-2-ylsulfanyl)-2-methylpropan-2-amine

Details on test material:

IUCLID4 Test substance: as prescribed by 1.1 - 1.4

Test animals

Species:

rabbit

Strain:

New Zealand White

Sex:

male/female

Administration / exposure

Type of coverage:

semiocclusive

Vehicle:

physiological saline

Details on exposure:

The test article, Santocure NS (N-tert-butylbenzothiazole-2-sulphenamide), was ground with a mortar and pesle and then moinstened with saline and mixed into a spreadable paste. It was applied evenly over each test site with a glass stirring rod at dosage levels of 125, 500 or 2000 mg/kg bw.

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

21 d

Frequency of treatment:

Five days per week for 3 consecutive weeks.

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 125, 500, or 2000 mg/kg bw/d
Basis:

No. of animals per sex per dose:

Five per sex and dose with intact skin, 5 per sex and dose with abraded skin.

Control animals:

yes

Details on study design:

Post-exposure period: no

Examinations

Observations and examinations performed and frequency:

Dosing was repeated once daily, five days per week for three consecutive weeks. Individual doses were adjusted weekly based on the body weight obtained at the beginning of each study week.
General observations: rabbits were observed once daily for signs of dermal irritation, daily observations for pharmacotoxic signs and other findings, the rabbits were observed for mortality twice daily.
Body weight: recorded weekly.
Hematology: hemoglobin, hemocrit, erythrocyte count, total leucocyte count, platelet count, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), reticulocytes, differential leucocyte count.
Biochemistry: glucose, blood urea nitrogen, serum glutamic oxaloacetic transaminase (SGOT), alkaline phosphatase, albumin, serum glutamic pyruvic transaminase (SGPT), total protein, cacium, cholesterol, total bilirubin, creatinine, lactic dehydrogenase (LDH), sodium, potassium, chloride and globulin.

Sacrifice and pathology:

Pathology: gross pathology.
Organ weights: liver, kidneys, heart, testes, ovaries, thyroid/parathyroid, adrenals and brain, pituitary.
Histopathology: treated and untreated skin, liver, kidneys and any gross lesions.
Recorded: erythema (score 0 to 3), edema (0 to3), atonia (0 to 3), coriaceousness (0 to 3), fissuring (0 to 3), eschar, exfoliation.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Description (incidence and severity):

No effects with the exception of a few spontaneous observations noted in all groups.

Dermal irritation:

effects observed, treatment-related

Description (incidence and severity):

Dermal irritation: The majority of rabbits in both the control and test groups exhibited no dermal irritation except for the following observations:
control group: a few rabbits exhibited very slight erythema, atonia and desquamation, and red raised areas and dry chappped areas on the shaved backs.
125 mg/kg bw/d: a few rabbits exhibited very slight to slight erythema, very slight desquamation and dry chapped areas on the shaven backs.
500 mg/kg bw/d: a few rabbits exhibited very slight erythema, very slight to slight desquamation and red and chapped areas on the shaven backs 2000 mg/kg bw/d: very slight to slight erythema and desquamation and very slight edema were exhibited by a few rabbits.

Mortality:

no mortality observed

Description (incidence):

No mortality were observed.

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

not specified

Food efficiency:

not specified

Water consumption and compound intake (if drinking water study):

not specified

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

Lymphocytes increased, neutrophiles, segmented decreased.
No other differences were noted in any of the treated animals compared to control (one male at 125/mg/kg bw/d and one male at 500 mg/kg bw/d had signs of aregenerative anemia)

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

Statistically significant differences compared to control were noted in:
125 mg/kg bw/d (males): total bilirubin decreased
2000 mg/kg bw/d (males): total bilirubin decreased 2000 mg/kg bw/d (females): LDH decreased no other differences were noted in any treatment group when compared to control

Urinalysis findings:

not specified

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

No statistically significant variations in the organ weights were noted in any of the test groups.

Gross pathological findings:

no effects observed

Description (incidence and severity):

No treatment related effects on skin at the application site in any of the rabbits from the test groups.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

2000 mg/kg bw/d: slight to moderate acanthosis and hyperkeratosis.
125, 500 mg/kg bw/d: the intensity of the acanthosis and hyperkeratosis was much less as in the highest dose group or almost similar to that observed in the control group.

Control group and treated animals: dermal inflammatory cell infiltration in all animals control and treated animals; however severity of this lesion was judged to be slightly greater in the 2000 mg/kg bw/d group compared to control. In the other two lower dosage groups, the intensity of this lesion was almost simular to that in the control group

Authors concluded: compound related effects consisting of acanthosis, hyperkeratosis and dermal inflammatory cell infiltrate were seen in the treated skin of rabbits from the 2000 mg/kg bw/d group but not in the two lower dosage groups in which these lesions were judged to be almost similar to those occurring in the control group.

Histopathological findings: neoplastic:

not examined

Other effects:

no effects observed

Effect levels

1

Dose descriptor:

NOAEL

Remarks:

systemic

Effect level:

> 2 000 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: No biologically relevant systemic effects

2

Dose descriptor:

NOAEL

Remarks:

local

Effect level:

500 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Acanthosis, hyperkeratosis, and dermal inflammatory cell infiltration in the treated skin of rabbits from the 2000 mg/kg

3

Dose descriptor:

LOAEL

Remarks:

local effects

Effect level:

2 000 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Acanthosis, hyperkeratosis, and dermal inflammatory cell infiltration in the treated skin of rabbits from the 2000 mg/kg

Target system / organ toxicity

Critical effects observed:

yes

Lowest effective dose / conc.:

2 000 mg/kg bw/day

System:

other: skin

Organ:

skin

Treatment related:

yes

Dose response relationship:

yes

Any other information on results incl. tables

General observations: No effects with the exception of a few spontaneous observations noted in all groups (control group: a few rabbits exhibited hair loss around neck in area of collar, right eye: red, swollen and clear discharge, possible anorexia, mucoid diarrhea and brown stain around anogenital region; treated animals: signs of mucoid stool, brown stain around the anogenital region, hair loss on neck in area of collar and soft stool were observed for all of the dosage levels; possible nasal congestion, diarrhea, mucoid diarrhea, soft stool, clear ocular discharge, possible anorexia and a spontaneous injury to back (impaired use hind leg) were also exhibited in the test groups.

Mortality: No mortality were observed.

Dermal irritation: The majority of rabbits in both the control and test groups exhibited no dermal irritation except for the following observations:

control group: a few rabbits exhibited very slight erythema, atonia and desquamation, and red raised areas and dry chappped areas on the shaved backs.

125 mg/kg bw/d: a few rabbits exhibited very slight to slight erythema, very slight desquamation and dry chapped areas on the shaven backs.

500 mg/kg bw/d: a few rabbits exhibited very slight erythema, very slight to slight desquamation and red and chapped areas on the shaven backs 2000 mg/kg bw/d: very slight to slight erythema and desquamation and very slight edema were exhibited by a few rabbits.

Body weights: No effects

Hematology: 500 mg/kg bw/d (males):

Lymphocytes increased, neutrophiles, segmented decreased.

no other differences were noted in any of the treated animals compared to control (one male at 125/mg/kg bw/d and one male at 500 mg/kg bw/d had signs of aregenerative anemia).

Biochemistry: Statistically significant differences compared to control were noted in:

125 mg/kg bw/d (males): total bilirubin decreased.

2000 mg/kg bw/d (males): total bilirubin decreased 2000 mg/kg bw/d (females): LDH decreased no other differences were noted in any treatment group when compared to control.

Macroscopic pathology: No treatment related effects on skin at the application site in any of the rabbits from the test groups.

Organ weights: No statistically significant variations in the organ weights were noted in any of the test groups.

Histopathology:

2000 mg/kg bw/d: slight to moderate acanthosis and hyperkeratosis.

125, 500 mg/kg bw/d: the intensity of the acanthosis and hyperkeratosis was much less as in the highest dose group or almost similar to that observed in the control group.

Control group and treated animals: dermal inflammatory cell infiltration in all animals control and treated animals; however severity of this lesion was judged to be slightly greater in the 2000 mg/kg bw/d group compared to control. In the other two lower dosage groups, the intensity of this lesion was almost simular to that in the control group

Authors concluded: compound related effects consisting of acanthosis, hyperkeratosis and dermal inflammatory cell infiltrate were seen in the treated skin of rabbits from the 2000 mg/kg bw/d group but not in the two lower dosage groups in which these lesions were judged to be almost similar to those occuring in the control group.

Applicant's summary and conclusion

Executive summary:

Study Design

Santocure NS (N-tert-butylbenzothiazole-2-sulphenamide) was administered by dermal application to 3 groups of 10 male and 10 female rabbits, one-half with intact skin and one-half with abraded skin, five days per week for 3 consecutive weeks at dose levels of 125, 500 or 2000 mg/kg. An identical control group was treated with saline. Criteria evaluated for treatment effect included mortality, pharmacotoxic signs, body weights, dermal irritation, hematological and clinical biochemical determinations, organ weights and macroscopic and selected microscopic evaluation of tissue.

 

Results

No mortality occurred in this study. The majority of rabbits in both the control and test groups appeared nomal with the exception of a few rabbits in all dose groups exhibiting occasional spontaneous pharmatoxic signs. No statistical significance was noted in body weights. No remarkable changes or differences in dermal irritation were observed between control and test groups. Statistically significant changes in hematological values occured in the 500 mg/kg males in lymphocytes and segmented neutrophils. A few statistically significant changes occurred in the biochemical values; 125 and 2000 mg/kg males showed a decrease in total bilirubin and 2000 mg/kg females showed a decrease in LDH.

 

No compound related macroscopic lesions or statistically significant organ weight variations were observed in this study.

 

Microscopically, compound related lesions consisting of acanthosis, hyperkeratosis, and dermal inflammatory cell infiltration were seen in the treated skin of rabbits from the 2000 mg/kg group. All other microscopic lesions observed were incidental in nature and not related to the application of the test substance.

 

Conclusion

Based on the results of the study, effects levels were determined as:

NOAEL for systemic effects: > 2000 mg/kg bw/day 

NOAEL for local effects: 500 mg/kg bw/day

LOAEL for local effects: 2000 mg/kg bw/day, based on the recording of acanthosis, hyperkeratosis, and dermal inflammatory cell infiltration in the treated skin of rabbits at this dose level.