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Toxicological information

Repeated dose toxicity: dermal

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Administrative data

Endpoint:
short-term repeated dose toxicity: dermal
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The study was conducted in the seventies, i.e. prior to implementation of guidelines, and GLP was not compulsory at that time. However, the study was well-documented and the reported data are of scientific accetability.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1973

Materials and methods

Principles of method if other than guideline:
Method: other: no data
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
not specified
Details on test material:
No purity specified.

Test animals

Species:
rabbit
Strain:
New Zealand White
Sex:
male/female
Details on test animals and environmental conditions:
Source: Hylyne Commercial Rabbits, Cheshire
They were housed individually in metal cages.

Administration / exposure

Type of coverage:
other: non-occlusive
Vehicle:
other: methylcellulose
Details on exposure:
Route of Administration: dermal
At a dose level of 1 ml/kg b.w. the daily application of Bronopol at a concentration of 0.2 and 0.5% corresponds to a dose of 2 and 5 mg/kg bw/day
respectively.
Vehicle: 2,5% methylcellulose.
The residual test substance was removed after each treatment period of 6 hours by gentle washing of the skin application site with a warm dilute soap solution, followed by rinsing with clean water; thereafter the skin was blotted dry with absorbent paper.
Duration of treatment / exposure:
21 days, 6 hours/day
Frequency of treatment:
7 d/week
Doses / concentrations
Remarks:
Doses / Concentrations:
1 ml/kg bw of 0.2 and 0.5 % bronopol in 2.5% methyl cellulose
Basis:

No. of animals per sex per dose:
5
Control animals:
yes, concurrent vehicle
Details on study design:
Post-exposure period: none

Examinations

Observations and examinations performed and frequency:
Observations and examinations included local skin reaction (erythema and oedema), behavioural changes and
signs of toxicity, food consumption, body weight, haematology (packed cell volume, haemoglobin, red cell count,
total and differential white cell count), clinical chemistry (plasma urea, total serum proteins, serum protein,
serum alkaline phosphatase, serum transaminase (SGPT), ophthalmoscopic examination.
Body weights were recorded at test initiation and weekly thereafter; the group mean value (g/rabbit) was calculated. Food consumption for each rabbit was recorded weekly and the group mean food intake (g/rabbit/week) was calculated. The eyes of the animals were examined prior test start and again after 3 weeks of treatment (Keeler indirect ophthalmoscope).
Sacrifice and pathology:
Terminal studies after sacrifice of the animals included macroscopic examination and weighing of inner organs
(thyroid, heart, liver, kidneys, adrenals, and gonads) and microscopic examination of a series of tissues
(adrenal, brain, duodenum, eye, gall-bladder, gonads, heart, ileum, kidney, liver, lymph nodes, marrow smear,
mid-colon, pancreas, pituitary, salivary gland, skin (treated and untreated), spleen, stomach
(glandular and non-glandular), thymus, thyroid, urinary bladder.
Statistics:
Student's t-test and analysis of variance were employed to assess the significance of intergroup differences.

Results and discussion

Results of examinations

Details on results:
Local skin reaction (slight to well-defined erythema in 9/10 animals, and slight edema in all animals)was observed in the control rabbits. Similar irritation was seen in rabbits treated with Bronopol 0.2% although possibly with slightly more edema formation and slightly more persistent.Bronopol 0.5% treatment caused progression of slight to well-defined erythema to moderate erythema in 9/10 animals. Edema occurred on the third day and became well defined in all rabbits. Moderate edema developed in 3/5 males. The macroscopical examination of the treated skin areas at necropsy revealed a varying degree of inflammatory reaction in control (2 cases) and in the 0.5% bronopol group (one case).One animal treated with 0.2% bronopol showed an isolated area of hyperkeratosis.One animals of the 0.2% bronopol group and 4 animals of the 0.5% bronopol group showed areas of dermal scarring(1 to 8 mm in length). All these reactions were considered to be non-specific and without toxicological significance. Areas of scabbing with associated dermal inflammation were seen in 2 animals treated with 0.5% bronopol. A similar effect also was seen in an animal of the 0.2% bronopol group, however within an untreated skin area. Therefore, this effect was considered to rather be related to the scarification of the skin than to the treatment with bronopol.
No mortality and no signs of toxicity were observed.
Food consumption of all male and female animals was normal except for 2 animals in group 2 (0.2%) and one animal in group 3 (0.5%) where food consumption was depressed.Initial loss of body weight was seen in all groups including controls; weight gain was comparable and no treatment related trend could be observed which would indicate a specific effect of Bronopol on growth.
Haematology and clinical chemistry were inconspicious.
Ophthalmoscopic examination revealed no abnormalities.
Neither gross- nor histopathological treatment-related changes were seen; organ weights were inconspicious.

Effect levels

open allclose all
Dose descriptor:
NOAEL
Effect level:
ca. 0.2
Based on:
test mat.
Remarks:
%
Sex:
male/female
Basis for effect level:
other: skin irritation
Dose descriptor:
LOAEL
Effect level:
0.5 other: %
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: skin irritation

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

Table 1: Numerical scores awarded to dermal reactions elicited by Bronopol

(group 1: vehicle control; 2: Bronopol 0.2%; 3: Bronopol 0.5%).

 Group Sex  Animal No.  Reaction   Day 0 1 14  21 
1  Male 324  Erythema 0 1 1 1 1 1
  Oedema 0 0 0 0 1 0
   469 Erythema  0 1 1 1 2 1
    Oedema 0 0 0 0 1 1
  478 Erythema 1 1 1 1 1 1
  Oedema 0 0 0 0 1 0
  2438 Erythema  0 1 1 1 1 1
  Oedema 0 0 0 0 0 0
  327 Erythema  0 1 1 1 1 1
  Oedema 0 0 0 0 1 0
   Female 350 Erythema  0 1 1 1 1 1
      Oedema 0 0 0 0 1 2
  2081 Erythema 1 1
      Oedema 0 1
    2082 Erythema 0 2
      Oedema 0 1
    332  Erythema  0
      Oedema
    344 Erythema 
      Oedema 0

Group Sex  Animal No.  Reaction   Day 0 1 14  21 
2  Male 326 Erythema 1 1 1 1 2 1
  Oedema 0 0 0 0 1 1
  330 Erythema  1 1 1 1 2 1
    Oedema 0 0 0 0 1 0
  476 Erythema 0 1 1 1 2 2
  Oedema 0 0 0 0 1 1
  2054 Erythema  1 1 1 1 2 1
  Oedema 0 0 0 0 1 0
  2473 Erythema  0 0 1 1 1 1
  Oedema 0 0 0 0 1 0
   Female 342 Erythema  0 1 1 2 1 2
      Oedema 0 0 0 0 1 2
  2089 Erythema 0 1
      Oedema 0 0
    2097 Erythema 0 1
      Oedema 0 1
    2092 Erythema  0 1 1
      Oedema 1 1
    2406 Erythema 
      Oedema

Group Sex  Animal No.  Reaction   Day 0 1 14  21 
3  Male 316 Erythema 0 2 2 2 3 3
  Oedema 0 0 0 1 3 2
  331 Erythema  0 2 2 2 3 3
    Oedema 0 0 0 1 3 2
  2057 Erythema 0 1 2 2 3 3
  Oedema 0 0 0 1 2 1
  2439 Erythema  0 1 1 1 3 3
  Oedema 0 0 0 1 3 3
  2055 Erythema  0 1 1 1 3 3
  Oedema 0 0 0 1 2 2
   Female 336 Erythema  0 1 1 1 3 3
      Oedema 0 0 0 1 2 2
  354 Erythema 0 2 3
      Oedema 0 2
    2083 Erythema 0 2 3
      Oedema 0 2
    335  Erythema  0
      Oedema
    337 Erythema 0 1 3
      Oedema 0 0 0 1 2

Applicant's summary and conclusion

Conclusions:
CL-Freetext:
Repeated dermal application of Bronopol at 0.2 and 0.5% in methyl cellulose suspension over a period of 21 days was not associated with signs of systemic toxicity or deaths. Severe skin irritation was observed after application of 0.5% Bronopol, whereas 0.2% Bronopol caused skin reaction comparable to, but slightly more persistent than that elicited by the vehicle alone. Correspondingly, NOAEL- and LOAEL-values were estimated on the basis of the skin findings.