Isohexadecyl 12-[(1-oxooctadecyl)oxy]octadecanoate

Dermal absorption

Administrative data

Endpoint:

dermal absorption in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

Acceptable, well documented study report which meets basic scientific principles.

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

2001

Report date:

2001

Reference 2

Reference Type:

secondary source

Title:

Unnamed

Year:

2001

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:

no

Test material

Test material information

Constituent 1

Radiolabelling:

yes

Test animals

Species:

other: human skin

Strain:

other: not applicable

Administration / exposure

Type of coverage:

open

Vehicle:

other: safflower oil

Details on study design:

DOSE PREPARATION
- 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.

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

ANALYSIS
- 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):

SKIN PREPARATION
- 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 < 2.0 x 10⁻³ 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.

PRINCIPLES OF ASSAY
- 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

Key result

Time point:

48 h

Dose:

10 g (10% in safflower oil)

Parameter:

percentage

Absorption:

>= 4 - < 5 %

Remarks on result:

other: 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.

Any other information on results incl. tables

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

Time (h)	µg/cm²	% applied dose
4	0.013 ± 0.005	0.003 ± 0.001
8	0.012 ± 0.003	0.002 ± 0.001
12	0.017 ± 0.006	0.003 ± 0.001
24	0.044 ± 0.004	0.009 ± 0.001
48	0.023 ± 0.005	0.005 ± 0.001

 

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

Site	% applied dose	µg/cm²
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

Conclusions:

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.