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Administrative data

dermal absorption in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
supporting study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Acceptable, well documented study report which meets basic scientific principles.

Data source

Referenceopen allclose all

Reference Type:
study report
Report date:
Reference Type:
secondary source

Materials and methods

Principles of method if other than guideline:
An in vitro human skin penetration study was performed, using radiolabelled test substance. The permeation rate and percentage of octyldodecyl stearoyl stearate through human skin over 48 hours was recorded.
GLP compliance:

Test material


Test animals

other: human skin
other: not applicable

Administration / exposure

Type of coverage:
other: safflower oil
Details on study design:
- Method for preparation of dose suspensions: 10 g 10% test substance in safflower oil, at a target activity of 100 µCi/g, was prepared. 15.92 mg 14C-octyldodecyl stearoyl stearate was transferred to a 20 mL vial and unlabelled octyldodecyl stearoyl stearate was added to make the total weight to 1.00153 g. Safflower oil (9.00048 g) was added to produce a solution that contained 10.01% octyldodecyl stearoyl stearate with a theoretical activity of 101.3 µCi/g.

The test substance dilution was applied to the skin surface at a concentration of 5 mg/cm².

- Method type(s) for identification: liquid scintillation counting
- Validation of analytical procedure: the donor activity was measured in 5 samples taken from the bulk application vehicle to ensure content uniformity. The mean measured donor activity was 101.9 µCi/g, and values varied by less than 1.5%.
Details on in vitro test system (if applicable):
- Source of skin: four female donors
- Ethical approval if human skin: no, the samples were obtained from cosmetic reduction surgery
- Type of skin: from the abdomen and breast area
- Preparative technique: the subcutaneous fat was removed from the skin samples by dissection using surgical forceps, scissors and scalpel, and the skin was heat-separated (60 °C for 45 seconds) to generate epidermal membranes. Each epidermal membrane was allowed to dry prior to being frozen, and thawed immediately prior to use. The epidermal membranes (supported on filter paper) were placed on the lower house of greased (silicone grease) diffusion cells, the stratum corneum facing the donor chamber. The upper halves of the diffusion cells were added and the assembly fixed together with pinch clamps.
- Membrane integrity check: the integrity of each membrane was assessed prior to the experiment by determining the permeation of ³H2O over 20 minutes. The skin samples showing water permeation rates greater than 2.0 mg/cm²/h (Kp < 0.002 cm/h) were rejected.
- Storage conditions: stored at -20 °C
- Justification of species, anatomical site and preparative technique: the technique provides separation of the dermis from the epidermis at the epidermal basal layer, generating membranes comprising the entire epidermis.

- Diffusion cell: Franz-type glass diffusion cells within area available for diffusion of about 1.0 cm² were used. The exact diffusion area was known for each diffusion cell.
- Receptor fluid: 6% Volpo N20 in pH 7.4 phosphate-buffered saline (known volume)
- Static system: the contents of the receptor chamber were continuously agitated by small magnetic followers driven by submersible magnetic stirrers
- Test temperature: the receptor chambers were maintained at 37.0 ± 1°C; the skin surface temperature was maintained at 32.0 ± 1°C
- Occlusion: none
- Other: 200 µL samples were taken from each receptor chamber at 4, 8, 12, 24 and 48 h (application time: 0 h). The 14C-content was determined by liquid scintillation counting. The liquid removed from each cell was replaced with temperature-equilibrated fresh receptor medium. At the end of the 48-h test period, radioactivity remaining on the skin surface and in the donor chamber (including the silicon grease) was removed by gently wiping with cotton buds, which were extracted with isopropyl myristate and tetrahydrofuran respectively, and the samples analysed for 14C-content. The skin samples were removed from this diffusion cell and tape-stripped 12 times using D-squame tape. Following the surface wipe and tape-stripping, the remaining epidermal membrane was solubilised using OptiSolve and assayed for 14C-content.

Results and discussion

Absorption in different matrices:
- Receptor fluid, receptor chamber, donor chamber (in vitro test system): less than 0.1% of the applied dose (see Table 1 under 'Any other information on results incl. tables')
- Skin preparation (in vitro test system): 4-5% (total amount in the skin, of which 3.021% in epidermis excluding tape strips)
- Stratum corneum (in vitro test system): 1.485% in tape strips
Total recovery:
- Total recovery: 98.7 ± 1.1% applied dose, of which 94.18% from the skin surface (see Table 2 under 'Any other information on results incl. tables')
Percutaneous absorption
Remarks on result:

Any other information on results incl. tables

Table 1: Octyldodecyl stearoyl stearate permeation data for all time points following application

Time (h)


% applied dose


0.013 ± 0.005

0.003 ± 0.001


0.012 ± 0.003

0.002 ± 0.001


0.017 ± 0.006

0.003 ± 0.001


0.044 ± 0.004

0.009 ± 0.001


0.023 ± 0.005

0.005 ± 0.001


Table 2: 48-h distribution data for octyldodecyl stearoyl stearate


% applied dose


48-h rinse

94.18 ± 1.39

477.4 ± 16.1

SC tape-strips 1-4

1.051 ± 0.162

5.33 ± 0.82

SC tape-strips 5-12

0.433 ± 0.101

2.18 ± 0.50

Remaining epidermis

3.021 ± 0.406

15.12 ± 1.90

Permeated (48 h)

0.005 ± 0.001

0.023 ± 0.005

Total recovery

98.69 ± 1.12



Applicant's summary and conclusion

Under the conditions of the study, permeation of octyldodecyl stearoyl stearate was very low. Following 48 h exposure to the 10% solution, between 4 and 5% of the applied dose was recovered from within the skin. The majority of the applied dose (94.18%) was recovered from the skin surface.