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Dermal absorption

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dermal absorption in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
weight of evidence
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference Type:
secondary source
Report date:

Materials and methods

Test guideline
according to guideline
OECD Guideline 428 (Skin Absorption: In Vitro Method)
not specified
GLP compliance:

Test material

Constituent 1
Chemical structure
Reference substance name:
Sodium 4-[(2-hydroxy-1-naphthyl)azo]benzenesulphonate
EC Number:
EC Name:
Sodium 4-[(2-hydroxy-1-naphthyl)azo]benzenesulphonate
Cas Number:
Molecular formula:
sodium 4-[(2-hydroxy-1-naphthyl)azo]benzenesulphonate

Test animals

not specified
not specified
Details on test animals or test system and environmental conditions:
12 animals

Administration / exposure

Type of coverage:
not specified
Duration of exposure:
30 minutes then washing with shampoo, diffusion monitored during 24 hours.
200 μL of the solution
Control animals:
neutral gel
Details on study design:
Porcine ear obtained from the slaughter house immediately after slaughter and before steam cleaning were used for this experiment. The outer ear region was washed, carefully shaved and the skin was removed by dissection. Thickness of the dissected skin was approximately 400-500 μm. The skin was mounted in glass flow-through diffusion chamber with area open to diffusion of 1 cm².
Each donor chamber was filled with 200 μl (200 mg) of the test item and covered (occluded) with Parafilm™. Saline, pH 3.0, was pumped through
the receptor chambers, with a flow rate of 1-2 ml/hour, and was collected in plastic vials which were replaced according to the sampling times and stored at – 20 °C.
The whole test system was set up in an incubator adjusted to 32 °C. After 30 min of contact the test item was removed from skin with shampoo solution.
Following the washing procedure the donor chamber were filled with 1ml of saline pH 3.0 for monitoring skin integrity during the 24 hours of diffusion). The collecting vials were changed after 0.5, 1, 2, 4, 6, 8 and 24 hours and D&C orange 4 was analyzed.
At the end of the experiment the epidermal membrane was separated from the full thickness skin by heat. This technique as described by the applicant removes the horny layer and part of the upper stratum germinativum from the rest of the skin (lower stratum germinativum and upper dermis).
After skin extraction the item bound in the tissues was quantified. Since the epidermis was separated from the dermis by heat separation method,
the amount of dye found in the upper skin is considered by the applicant not to have passed the skin. The amount of penetrated test item found in the receptor solution plus that found in the lower skin extracts are considered as penetrated respectively absorbed.

Results and discussion

Signs and symptoms of toxicity:
no effects
Dermal irritation:
no effects

Applicant's summary and conclusion

No measurable permeation through the skin occurred at any time point within the time frame of both experiments.
Executive summary:

No measurable permeation through the skin occurred at any time point within the time frame of both experiments. The lowest detection limit under the conditions reported is 0.08 μg/ml in the first and 0.078 μg/ml in the second experiment. The maximal possible, calculated amount of the test item diffusing across the skin barrier is 1.2 μg/cm² in the first and 1.1 μg/cm2 in the second experiment. Together with the lower skin extract, the worst case consideration of penetrated test item is 2.4 μg/cm² (0.26% of the applied dose) in the first and 4.2 μg/cm² (0.37% of the applied dose) in the second experiment. It has to be emphasised that the values of the absorption without the lower skin are calculated and do not reflect real penetration. The mean recovery of the test item was 107.9% in the first and 92.9% in the second experiment.