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Dermal absorption

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Administrative data

dermal absorption in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study performed according to GLP and OECD guideline 428

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guideline
according to guideline
OECD Guideline 428 (Skin Absorption: In Vitro Method)
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Chemical structure
Reference substance name:
EC Number:
Cas Number:
Molecular formula:
14C WP30

Administration / exposure

Details on in vitro test system (if applicable):
- Source of skin: Human (3 donors)
- Ethical approval if human skin: Human skin was obtained from abdominal surgery
- Preparative technique: the excised skin was was stored frozen at -20 °C. Only one freeze and thaw cycle was allowed. After thawing at room temperature, the skin was prepared using a dermatome.
- Thickness of skin (in mm): 0.3 +/- 0.1
- Membrane integrity check: evaluated before use by measuring the TEWL (trans-epidermal water loss). The Tewameter is a device for measurement of water evaporation from skin surfaces based on the diffusion principle. The human skin was included in the study if the TEWL was ≤ 13 +/- 3 g/m2/h

- Diffusion cell: static cells consisted of a donor chamber and a receptor chamber separated by the prepared skin. Dimensions: application area = 2 cm2
- Receptor fluid: volume 7 ml
- Solubility of test substance in receptor fluid: The saturation of WP30 in NaCl 0.9% containing BSA at 3% was demonstrated to be 4.56 µg/mL. Consequently, no saturation, no saturation of WP30 was observed in the receptofr fluid.
- Test temperature: 32 +/- 1 °C

Results and discussion

Absorption in different matrices:
- Receptor fluid, receptor chamber, donor chamber (in vitro test system): 0.01 % (SD 0.01)
- Skin preparation (in vitro test system):
Epiderm: 0.09 % (SD 0.1)
Derm 0.0085 (SD 0.0095)
- Stratum corneum (in vitro test system): (i.e tape strips): 0.26 % (SD 0.24)
Percutaneous absorption
0.5 mg/cm2
0.11 %
Remarks on result:
other: 24 hours
+/- 0.11 % (0.33 % according to SCCS recommandation
Conversion factor human vs. animal skin:
Assay performed on human excised skin

Applicant's summary and conclusion

The absorbed fraction of the applied WP30 for the formulation was 0.33% of the applied dose corresponding to 1.7 meq/cm2 according to the SCCP/0970/06 guidance.
The absorbed fraction of the applied WP30 for the formulation was 0.17% ± 0.32% (mean ± 2 SD) of the applied dose according to the SCCS/1358/1 0 guidance.
Executive summary:

The aim of this study was to investigate the rate and extent of the in-vitro dermal absorption of WP30 following topical application of the preparation (emulsion) to the surface of human skin mounted on static cells.

Test system: Human skin prepared using a dermatome

Number: 3 donors, 6 cells per donor

Test item: WP30

Formulation: 10% WP30(w/w)corresponding to 10 mg of WP30 for 100 mg of formulation. Around 0.5µCi (14C WP30) was applied on each cell (10 mg of formulation/cell, 5 mg/cm2


Receptor fluid  



Stratum corneum (tape Strips)

Product excess on the skin (Washing solution)

Exposure: 24 hours


The individual total recovery of the radioactivity was between:

88% and 100% for the donor 1 . 87% and 98% for the donor 2. 94% and 101 % for the donor 3

All receptor compartment fluid analyses were BLQ with the exception of cell A at 30 min and cell C at 4 hours indicating that 14C WP30 did not readily penetrate all the way through the skin samples.

According to theSCCP/0970106guidance, the absorbed fraction is considered to be the sum of the radioactivity measured in epidermis, dermis and receptor fluid.

The absorbed fractions were between:

0.33% and 0.04% for the donor 1 0.12% and 0.02% for the donor 2, 0.16% and 0.03% for the donor 3.

According to the SCCP/0970/06 guidance (March 2006), if the CV% was greater than 30%, the higher value was considered for the absorption. Consequently, the absorbed amount of WP30 was 1.7 nqeq/cm2 corresponding to 0.33% of the applied dose.

According to the SCCS/1358/10 (June 2010), the mean±SD was used for the margin of safety calculation. In case of significant deviations from the protocol and/or very high variability, the mean±2 SD was used as dermal absorption for the calculation of the margin of safety. In this report, we have chosen to present all calculations due high variations obtained link to skin variability and low values but not to any significant deviations to the testing procedures.

The (mean±SD) and (mean±2 SD) absorbed fractions are presented:

For donor 1: 0.17%±0.16% (mean±SD), 0.17%±0.32% (mean±2SD) corresponding to 0.49%, CV=94%.

For donor 2: 0.05%±0.04% (mean±SD), 0.05%±0.08% (mean±2SD) corresponding to 0.13%, CV=73%

For donor 3: 0.10%±0.06% (mean±SD), 0.10%±0.12% (mean±2SD) corresponding to 0.22%, CV=57%

According to that, the absorbed amount of WP30 was 0.49%.


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