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Dermal absorption

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Administrative data

Endpoint:
dermal absorption in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
21 April - 24 August 2006
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2006
Report Date:
2006

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 428 (Skin Absorption: In Vitro Method)
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Product name: Antiblaze TL-10-ST
- Test material name: [14C]-TL-10-ST
- Radiochemical purity: consistent with Antiblaze TL-10-ST standard
- Specific activity: 23 mCi/mmol
- Storage of radiolabelled test material: -20 degree C
Radiolabelling:
yes

Test animals

Species:
human

Administration / exposure

Type of coverage:
open
Vehicle:
other: neat substance and ethanol (2 experiments)
Duration of exposure:
Exposed skin surface was washed and dried 8 hours after dosing. At 24 hours after dosing the diffusion cells were disconnected and the skin washed and analysed by liquid scintillation couting.
Doses:
- [14C]-TL-10-ST: neat, application rate: 14.03 mg equiv./cm2
- [14C]-TL-10-ST in ethanol: 20.96 g/L, application rate: 0.210 mg equiv./cm2
Details on study design:
8 samples were dosed topically with undiluted radiolabelled test material and 8 samples with the radiolabelled test material in ethanol at a concentration of 20.96 g/L..
Details on in vitro test system (if applicable):
SKIN PREPARATION
- Source of skin: 6 samples of full-thickness human skin
- Ethical approval: skin from patients undergoing surgery at the Plastic Surgery Unit of St Johns Hospital in Livingston, UK
- Type of skin: 1 abdomen, 5 breast
- Preparative technique: split-thickness membranes
- Thickness of skin (in mm): 0.2 - 0.4
- Membrane integrity check: yes

PRINCIPLES OF ASSAY
- Diffusion cell: Automated flow -through cell apparatus (Scott/Dick, University of Newcastle-upon-Tyne, UK)
- Receptor fluid: physiological saline (0.9% w/v) for barrier integrity assessment, ethanol:water (1:1 v/v) for test item permeability test
- Occlusion: no

Results and discussion

Absorption in different matrices:
Neat test item
- Skin wash: dislodgeable dose after 8 h: 99.3 % +- 5.92% (range 89.21 - 106.76%), after 24 h: 102.63% +- 3.05% (range: 99.89 - 106.89%)
- Skin test site: dermal delivery (sum of absorbed dose and dose on recovered on the skin): 0.51 % +- 0.5% (range: 0.05 - 1.48%), 72.04 +- 69.74 micro g-equivalent/cm2
- Receptor fluid, receptor chamber: 0.19 % +- 0.18% (range: 0.01 to 0.55%)
- Stratum corneum (in vitro test system): (i.e tape strips): 1,83 % +- 1.67% (range: 0.19 - 4.63%), 1.36 % +- 1.25% (range 0.1 - 3.5%) removed with the first 5 tape strips
- Steady state flux was achieved from 14 to 24 h post dose: 1.10 microg-equiv/cm2
- the absorbed dose was 26.95 +- 25.27 microg equiv/cm2

Test item in Ethanol (20.96 g/L):
- Skin wash: dilodgeable dose after 8 h: 68.82 % +- 20..05% (range: 42.26 to 88.91%) , at 24 h further: 9.28% +- 8.84%, total dislogeable dose: 78.1 %+- 16.2% (range: 57.49 -95.25%)
- Skin test site: dermal delivery (sum of absorbed dose and dose on recovered on the skin): 6.1 % +- 4.20% (range: 0.82 - 12.14%)
- Receptor fluid, receptor chamber: 2.19 % +- 1.77% (range: 0.73 - 6.26%)
- Stratum corneum (in vitro test system): (i.e tape strips): 9.71 % +- 6.13% (range: 1.16 - 16.78%), 5.79 % +- 3.74% (range 0.56 - 9.56%) removed with the first 5 tape strips
- Steady state flux was achieved from 2 to 5 h post dose: 0.24 microg-equiv/cm2
- the absorbed dose was 4.6 +- 3.72 microg equiv/cm2

Total recovery:
All samples had a mass balance within 100+-10% (one cell rejected because of incomplete receptor fluid collections)
Total recovery 105.03 % for neat substance, 98.57 % for the test substance in Ethanol.
Percutaneous absorptionopen allclose all
Parameter:
percentage
Absorption:
0.2 %
Remarks on result:
other: 24h post dose
Remarks:
radiolabelled neat test substance
Parameter:
percentage
Absorption:
2.2 %
Remarks on result:
other: 24h post dose
Remarks:
radiolabelled test sustance in ethanol

Any other information on results incl. tables

- Dermal delivery (sum of the absorbed dose and amount in skin) of the test substance was 0.51% +- 0.5 (72.04 microg equiv./cm2) and 6.10% (12.78 microg equiv./cm2) for the test substance in ethanol

- Steady state flux was achieved for the neat test substance from 14 -24h, and from 2 -5h for the test substance in ethanol

- The mass balance was complete for the test substance (105.03%) and the test substance in ethanol (98.57%).

- The majority of the dose was not aborbed and could be removed by washing.

Applicant's summary and conclusion

Conclusions:
Following topical application to human skin in vitro for 8 h, the absorbed dose of the neat test substance after 24 h was 0.19% (26.95 microg equiv/cm2), and 2.19% for the test substance (20.96 g/L) in ethanol (4.60 microg equiv/cm2). Dermal delivery was 0.51% (72.04 microg-equiv/cm2) and 6.1% (12.78 microg/equiv/cm2) respectively. The majority of the dose (102 and 78 % respectively) did not penetrate the skin and coudl be removed by washing. Further 1.4 and 5.8% of the dose respectivly could be removed in the first 5 tape strips i.e. on the stratum, corneum surface and not associated with the skin.










Executive summary:

In an in vitro skin absorption study 8 human skin samples were treated with radiolabelled 2,2 -bis(chloromethyl)trimethylene bis(bis(2 -chloroethyl)phosphate) either undiluted or at a concentration of 20.96 g/L in ethanol at application rates of 14.03 mg equiv./cm2 and 0.210 mg equiv./cm2 respectively for 8h under open condittions. Sampling continued after washing at 8h until 24 hours after dosing.

Dermal delivery of the test substance was 0.51% (72.04 microg equiv./cm2) and 6.10% (12.78 microg equiv./cm2) for the test substance in ethanol.

The absorbed dose of the test substance was 0.19% (26.95 microg equiv/cm2), and 2.19% for the test substance in ethanol (4.60 microg equiv/cm2).

This study is classified as valid without restrictions and is conducted in accordance with GLP regulations and OECD Guideline No.428 and OECD Guidance document No.28.