Registration Dossier

Administrative data

Endpoint:
dermal absorption in vivo
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study well documented, meeting generally accepted scientific principles, acceptable for assessment.

Data source

Reference
Reference Type:
publication
Title:
Percutaneous absorption of α-olefin sulfonate (AOS) in rats.
Author:
Minegishi, K. et al.
Year:
1977
Bibliographic source:
Chem Pharm Bull 25(4): 821-825

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Study was performed before actual guideline was established
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Test material form:
other: aqueous formulation
Details on test material:
- Name of test material (as cited in study report): α-olefin sulfonate (AOS)
- Substance type: surfactant
- Physical state: solution
- Analytical purity: not specified
- Composition of test material, percentage of components: 55 % 3-hydroxytetradecene-1-14C sulfonate, 45 % beta-tetradecene-1-14C sulfonate
- Radiochemical purity (if radiolabelling): 98 %
- Specific activity (if radiolabelling): 6.55 µCi/mg
- Locations of the label (if radiolabelling): C1
- Other: Source: Daiichi Pure Chemicals Co., Ltd., Tokyo
Radiolabelling:
yes
Remarks:
14C

Test animals

Species:
rat
Strain:
Wistar
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Weight at study initiation: 360-380 g

Administration / exposure

Type of coverage:
other: open and occlusive, respectively
Vehicle:
water
Duration of exposure:
0.5, 1.5, 24 hours intact skin; 30 hours damaged skin
Doses:
- Nominal doses: open: 0.5 ml of 0.2 % (w/v) 14C-AOS (6.00 µCi or 5.88 µCi/0.5 ml); occlusive: 10 ml of 0.02 % (w/v) 14C-AOS (11.7 µCi/10 ml)
No. of animals per group:
3 - 8
Control animals:
no
Details on study design:
DOSE PREPARATION
- Method for preparation of dose suspensions: preparation of an aqueous solution


APPLICATION OF DOSE:
Five conditions were employed for the application of 14C-AOS: 1) the intact skin dried naturally after application, 2) the intact skin wiped off 0.5 hours after application, 3) the intact skin wiped off 1.5 hours after application, 4) the intact skin with a plastic cup containing 14C-AOS solution (cup method) and 5) the damaged skin without the stratum corneum dried naturally after application.
The cup method was employed to bring the surfactant solution into contact with the skin at all the time.

TEST SITE
- Preparation of test site: The dorsal hair of each animal was closely clipped to expose the skin and 0.5 ml of a 0.2 % (w/v) solution was applied to the marked area of the skin with a stomach tube, except the occlusive method (cup method). The cup method comprised a plastic ice-making cup (4x4x3 cm) that was reversely attached to the dorsal clipped area of rats with Aron Alpha, a quick set adhesive (Toa Gosei Chemical Industries Co., Ltd). The test substance solution was filled through a hole in the bottom which was subsequently sealed with a cellophane tape.

The damaged skin was prepared by 20-time treatments of the dorsal skin with a cellophane adhesive tape (width: 50 mm, length: 70 mm, Nichiban Co., Ltd.) to remove the stratum corneum, according to the method of Washitake et al. (1973).

- Area of exposure: 4x3 cm open (4x4 cm cup method, occlusive)
- Type of cover / wrap if used: plastic ice-making cup for occlusive application
- Time intervals for shavings or clipplings: only before application


SITE PROTECTION / USE OF RESTRAINERS FOR PREVENTING INGESTION: no, only for cup method


REMOVAL OF TEST SUBSTANCE
- Removal of protecting device: not applicable
- Washing procedures and type of cleansing agent: either not washed (naturally dried) or wiped off after application 10-times with absorbent cotton balls wet with water (diam. 1 cm).
- Time after start of exposure: 0.5 or 1.5 hours (if wiped)


SAMPLE COLLECTION
Collection of bile and urine by bile-duct and bladder cannulation at regular intervals after application: 0-1, 1-3, 3-6, 6-9, 9-12, 12-24, (24-30 only damaged skin) hours.
- Terminal procedure: not specified
- Analysis of organs: Following sacrifice the organs were removed and weighed, the distribution of radioactivity was determined in brain, lung, liver, kidney and spleen 24 hours after application.


ANALYSIS
- Method type(s) for identification: Liquid scintillation counting

Results and discussion

Signs and symptoms of toxicity:
not specified
Dermal irritation:
not specified
Absorption in different matrices:
- Skin wash: 60 - 70 % of the total radioactivity applied was recovered from the skin
- Urine: total recovery 0.298 % after 24 hours (application on intact skin)
- Cage wash + cage wipe: not applicable, cannulation of bladder
Total recovery:
- Total recovery: Intact skin: 0.62 % of dose 24 hours after application; damaged skin: about 50 % of dose

Percutaneous absorption
Dose:
0.2% (w/v)
Parameter:
percentage
Absorption:
0.62 %
Remarks on result:
other: 24 h
Remarks:
open application

Any other information on results incl. tables

The biliary and urinary excretion of radioactivity was determined in rats after dermal application of 14C-AOS to intact and damaged skin.

Biliary and urinary excretion of radioactivity in rats applied 14C-AOS:

Time after application (h)

Intact skin (% of applied dose)*

Damaged skin (% of applied dose)**

Bile

Urine

Bile

Urine

0 - 1

trace

trace

0.203 ± 0.138

3.457 ± 3.165

1 - 3

0.006 ± 0.003

0.022 ± 0.017

0.480 ± 0.277

11.305 ± 3.942

3 - 6

0.013 ± 0.005

0.048 ± 0.017

0.361 ± 0.249

7.359 ± 3.486

6 - 9

0.010 ± 0.003

0.054 ± 0.014

0.196 ± 0.110

5.003 ± 2.322

9 - 12

0.009 ± 0.005

0.047 ± 0.011

0.127 ± 0.032

3.907 ± 1.782

12 - 24

0.019 ± 0.007

0.127 ± 0.024

0.329 ± 0.063

4.169 ± 3.868

24 - 30

--

--

0.130 ± 0.032

1.059 ± 0.559

Mean values are given ± S.E.

*Five animals used.

**Three animals used.

The radioactivity appeared in bile and urine within 1 hour after application, but it was very low. Total recoveries of the radioactivity were 0.298 % in the urine and 0.057 % in the bile 24 hours after application.

The distribution of radioactivity was examined in various organs 24 hours after application. The radioactivity did not show significant affinity for those organs under this experimental condition.

Distribution and total recovery of radioactivity in rats applied 14C-AOS:

Organ

Intact skin (24 h)*

Damaged skin (30 h)*

dpm/g

% of applied dose

dpm/g

% of applied dose

Brain

856 ± 100

0.010 ± 0.001

3066 ± 800

0.042 ± 0.010

Lung

998 ± 173

0.012 ± 0.002

93051 ± 62822

1.461 ± 0.861

Liver

1419 ± 547

0.123 ± 0.037

113536 ± 17262

9.876 ± 2.013

Kidney

2975 ± 1561

0.059 ± 0.032

36383 ± 10871

0.871 ± 0.316

Spleen

2136 ± 535

0.004 ± 0.001

12336 ± 676

0.027 ± 0.004

Urine

--

0.327 ± 0.077

--

36.259 ± 18.203

Bile

--

0.083 ± 0.032

--

1.826 ± 0.823

Total

--

0.618

--

50.362

Mean values are given ± S.E.

*Three animals used.

Since 14C-AOS absorbed from the intact skin was very low, it might be rapidly metabolized in the liver to be excreted into the urine through the kidney. Total recovery of radioactivity from urine, bile and main organs was about 0.62 % of dose 24 hours after application.

The total amount of radioactivity absorbed from damaged skin was approximately 80 times that from the intact skin. The recoveries of radioactivity were 36.26 % in the urine and 1.83 % in the bile 30 hours after application. The distribution of radioactivity in the main organs was much larger than that of intact skin, with radioactivity in the liver being in excess compared with the other organs. the significance of the high accumulation of radioactivity in the lung was obscure, because the values varied remarkably in each animal. Total recovery was about 50 % of dose after application to damaged rat skin.

The recoveries of radioactivity in bile and urine were compared under the various conditions tested in the study, when 14C-AOS was applied to intact skin.

Comparison of biliary and urinary excretion of radioactivity in rats applied 14C-AOS under various conditions:

Condition

Animal number

% of applied dose 24 h after application

Bile

Urine

1) Applied alone

8

0.051 ± 0.015

0.329 ± 0.044

2) Applied and wiped off 0.5 h after application

3

0.023 ± 0.011

0.100 ± 0.008

3) Applied and wiped off 1.5 h after application

3

0.043 ± 0.007

0.367 ± 0.069

4) Cup method

3

0.025 ± 0.012

0.092 ± 0.032

Mean values are given ± S.E.

The recoveries of radioactivity in the bile and urine were considerably lower if the application site was wiped 0.5 hour after application, compared to wiping off the application site after 1.5 hours or not wiping off, at all. The fact that there was no significant difference between the latter two alternatives demonstrated, that the percutaneous absorption of AOS was almost finished at most by 1.5 hours after application, because longer exposure did not produce higher excretion of radioactivity. This conclusion was supported by the observation that the surfactant applied to the skin was dried naturally between 0.5 and 1 hour. The time-courses of biliary and urinary excretion were comparable under all conditions. The excretion rates approached maximum around 3-9 hours, then gradually decreased, and continued even 70-90 hours after application.

When 10 ml of 0.02 % 14C-AOS solution were continuously in contact with the skin in the cup method, the recoveries of radioactivity were rather low compared with using an initial concentration of 0.2 % and not wiping off. On the other hand, 14C-AOS seemed to be continuously absorbed from the skin under this condition.

Applicant's summary and conclusion