Registration Dossier

Administrative data

Endpoint:
dermal absorption in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2006
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP study according to OECD 428 guideline

Data source

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

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 428 (Skin Absorption: In Vitro Method)
Qualifier:
according to
Guideline:
other: In Vitro Dermal Absorption Rate Testing of Certain Chemicals of Interest to the Occupational Safety and Health Administration. Federal Register: April 26, 2004 (Volume 69, Number 80)
Qualifier:
according to
Guideline:
other: OECD Guidance document for the Conduct of Skin Absorption Studies. OECD Environment Health and Safety Publication Series on Testing and Assessment No. 28 (2004)
Qualifier:
according to
Guideline:
other: European Commission Document on Dermal Absorption. Sanco/222/2000 rev 6 (2004)
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Dipropylene Glycol Methyl Ether (DPGME)
- Physical state: Liquid
- Analytical purity: 100%
- Isomers composition: 2,2-54.45%, 2,1-2.83%, 1,2-40.20%, 1,1-2.52%
- Lot/batch No.: H27215
- Stability under test conditions: The test substance appeared to be stable under the conditions of the study
Radiolabelling:
no

Test animals

Species:
human
Strain:
not specified
Sex:
not specified

Administration / exposure

Type of coverage:
occlusive
Vehicle:
unchanged (no vehicle)
Duration of exposure:
10 min and 60 min
Doses:
The test substance was applied neat. The concentration of DPGME was taken at its density, 950 mg/ml (950,000 µg/cm3)
- Dose volume: 30 µL/cm2
No. of animals per group:
not applicable
Details on study design:
ANALYSIS
- Method type(s) for identification: GC-FID
- Validation of analytical procedure: yes
- Limits of detection and quantification: Based on the system response to DPGME the LOQ was equivalent to the lowest standard, 0.05 μg/mL. The average GC-FID method precision was 56-132%. Accuracy for the method, based on quality control samples, was 82-133%.
- System: Hewlett Packard (HP) 6890 Gas Chromatograph
- Column: HP Wax, 30 m x 0.53 mm x 1.0 μm
- Injector temperature: 250°C
- Detector temperature 260°C
- Oven temperature 120°C (Isothermal)
- Injection volume 3 μL
- Carrier gas Helium
- Carrier gas flow 35 mL/min
- Detector Flame Ionization Detector (FID)



Details on in vitro test system (if applicable):
SKIN PREPARATION
- Source of skin: Samples of human cadaver skin from the National Disease Research Interchange were stored frozen at approximately-20º C until prepared for use. Samples were donors within 24 hours of death and used within three months.
- Ethical approval if human skin: Not specified
- Type of skin: Human Cadaver skin
- Preparative technique: Samples of human cadaver skin obtained from the abdominal region, which were stored frozen, were thawed at room temperature. Full thickness skin was immersed in 60º C water for 45 sec to 2 min and the epidermis peeled away from the dermis.
- Membrane equilibration: Membranes were removed from refrigeration storage and hydrated in saline for approximately 15 minutes. Following hydration, the membrane was mounted onto the top of the receptor chamber, stratum corneum uppermost, which was maintained with saline. The donor chamber was then clamped in place and filled with saline. The membrane was then allowed to equilibrate for approximately 30 minutes. During equilibration, the in vitro cells were heated using a recirculating water bath system to yield a receptor fluid temperature of 32°C.
- Thickness of skin (in mm): Not specified
- Membrane integrity check: The integrity of each membrane was assessed by measurement of electrical impedance (EI) prior to application of the test substance. Membranes with an EI of ≥ 17 kΩ were considered intact and retained for use on study.
- Storage conditions: The human epidermal membrane was placed onto an aluminium pan, with its code embossed or written on the pan, and stored refrigerated at 0-10º C until readied for use
- Justification of species, anatomical site and preparative technique: Dermal contact is a potential route of human exposure. In vitro dermal techniques, which are required by the test rule described in the Federal Register dated April 26, 2004 (Volume 69, Number 80), have been shown to be conservative model for predicting percutaneous absorption of various chemicals in vivo.


PRINCIPLES OF ASSAY
- Diffusion cell: A static diffusion cell model was used for this study. The in vitro cells had an exposure area of 0.64 cm2.
- Receptor fluid: Receptor fluid chamber volume was approximately 5 mL. Receptor chamber was filled with fresh saline.
- Test temperature: Receptor fluid temperature was 32º C.
- Occlusion: Following dose application, the donor chamber opening was occluded with parafilm.

Results and discussion

Absorption in different matrices:
- Skin wash/rinse: Following a 10-minute exposure to a finite application of DPGME, 71.7 µg of DPGME (mean) was detected in the receptor fluid and skin respectively and following a 60-minute exposure to a finite application of DPGME, 146.2 µg (mean) of DPGME was detected in the receptor fluid and skin respectively.
- Skin: Following a 10-minute exposure to a finite application of DPGME, 70.0 µg (mean) of DPGME was detected in skin and following a 60-minute exposure to a finite application of DPGME, 105.7 µg (mean) of DPGME was detected in skin.
- Receptor fluid (in vitro test system): Following a 10-minute exposure to a finite application of DPGME, 1.66 µg of DPGME was detected in the receptor fluid and following a 60-minute exposure to a finite application of DPGME, 40.6 µg of DPGME was detected in the receptor fluid.
Total recovery:
- Total recovery: 10 minutes-87.7 and 60 minutes-88.6 (percent of applied dose)
- Recovery of applied dose acceptable: yes

Percutaneous absorptionopen allclose all
Remarks on result:
other: 10 minutes
Remarks:
Based on the amount of DPGME in the receptor fluid and skin, an exposurearea of 0.64 cm2, and an exposure time of 10 minutes (0.17 hours), the 10-minute absorption rate was calculated to be 658.6 μg/cm2/h.
Remarks on result:
other: 60 minutes
Remarks:
Based on the amount of DPGME in the receptor fluid and skin, an exposurearea of 0.64 cm2, and an exposure time of one hour, the 60-minute absorption rate was calculated to be 228.5 μg/cm2/h.

Applicant's summary and conclusion

Conclusions:
The ten minute absorption rate was calculated to be 658.6 µg/cm2/h and for 60 minute, the absorption rate was calculated to be 228.5 µg/cm2/h.

Executive summary:

Dipropylene Glycol Methyl Ether (DPGME), 100% pure, liquid was evaluated for in vitro dermal absorption rate testing following OECD guideline 428 and European Commission and OECD guidance document on Skin Absorption.

The short-term absorption rates at 10 and 60 minutes have been determined for dipropylene glycol methyl ether (DPGME) using human abdominal skin from cadavers mounted in an in vitro static diffusion cell model. Human cadaver skin was heat-treated at approximately 60°C and the epidermis was peeled from the dermis and the section mounted onto an in vitro static diffusion cell, stratum corneum uppermost, with an exposure area of 0.64 cm2. Using a recirculating water bath system, the receptor fluid (saline) was set at 32°C. Following system equilibration, skin integrity was confirmed by electrical impedance (EI). The saline in the donor and receptor chambers was removed and discarded and the receptor chamber was filled with fresh 0.9% saline.

DPGME was applied to the epidermal surface, via the donor chamber, to 12 skin replicates representing 3 human subjects at 30 μL/cm2, and the donor chamber opening was occluded with Parafilm®. At the end of the required exposure interval (10 minute and 60 minutes), 6 replicates each were terminated. At termination, the skin surface was washed with a 2% soap solution, rinsed with water, and the receptor fluid was removed and retained for analysis. The receptor and donor chambers were filled with saline and end of experiment integrity assessment was taken using EI. The skin section was removed and placed in a glass vial and extracted with water. Samples of receptor fluid, skin wash/rinse, and skin extract were analyzed by GC-FID for total DPGME.

Following a 10-minute exposure to a finite application of DPGME, 1.66 μg and 70.0 μg of DPGME were detected in the receptor fluid and skin, respectively. Based on the amount of DPGME in the receptor fluid and skin, an exposure area of 0.64 cm2, and an exposure time of 10 minutes (0.17 hours), the 10-minute absorption rate was calculated to be 658.6 μg/cm2/h. Following a 60-minute exposure to a finite application of DPGME, 40.6 μg and 105.7 μg of DPGME were detected in the receptor fluid and skin, respectively. Based on the amount of DPGME in the receptor fluid and skin, an exposure area of 0.64 cm2, and an exposure time of one hour, the 60-minute absorption rate was calculated to be 228.5 μg/cm2/h.