Registration Dossier

Administrative data

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

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2013
Report Date:
2013

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 428 (Skin Absorption: In Vitro Method)
GLP compliance:
yes (incl. certificate)
Remarks:
BASF SE Experimental Toxicology and Ecology 67056 Ludwigshafen, Germany

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
other: liquid
Details on test material:
Radiolabeled test substance:
- Name of test material (as cited in study report): 14C-Pyranol
- IUPAC name: 2-isobutyl-4-methyl-tetrahydro-2H-pyran-4-ol
- Test substance No.: 12/0466-1
- Batch No.: CFQ41575
- Radiochemical purity (if radiolabelling): > 98%
- Locations of the label (if radiolabelling): 4-methyl-C14
- Specific activity of AI: 12.4 MBq/mg (calculated)
- Concentration of AI: 6.8 mg/g test substance solution
- Specific activity: 84.2 MBq/g test substance solution
- Stability under test conditions: verified by analysis before start and at the end of application
- Storage condition of test material: storage in a refrigerator is considered appropriate for the limited study duration

Non-labeled test substance:
- Name of test material (as cited in study report): Pyranol
- IUPAC name: 2-isobutyl-4-methyl-tetrahydro-2H-pyran-4-ol
- Physical state: liquid/ colorless, clear
- test substance No.: 09/0639-2
- Batch No.: 00017277L0
- Purity: 99.6 area-%
- Stability under test conditions: 04 Jan 2014
- Storage condition of test material: ambient; under light exclusion
Radiolabelling:
yes
Remarks:
14C-Pyranol

Test animals

Species:
rat
Strain:
other: Crl:WI (Han) (SPF)
Sex:
not specified
Details on test animals and environmental conditions:
not applicable (in vitro study with dermatomed rat skin preparations)

Administration / exposure

Type of coverage:
other: donor chambers were covered with Fixomull® Stretch adhesive fleece after application (semi-occlusive conditions)
Vehicle:
corn oil
Duration of exposure:
8 hours
Doses:
9500 µg/cm² (pure Pyranol) and 1000 µg/cm² (solution in corn oil)
No. of animals per group:
5 diffusion cells for each dose
Control animals:
no
Details on study design:
DOSE PREPARATION
- Method for preparation of dose suspensions:

Pure Pyranol: To obtain the desired specific activity, a respective aliquot of the radiolabeled test substance was taken and the organic solvent (n-pentane) was evaporated to dryness. An adequate amount of the unlabeled pyranol was added to the dried residue in two steps. The nominal concentration of the test substance was 1000.0 mg/g (corresponding to 950.0 mg/mL). The nominal specific activity in the test substance preparation was 3.90 MBq/g (corresponding to 3.71 MBq/mL).

Solution in corn oil: A respective aliquot of the radiolabeled test substance was taken and the organic solvent (n-pentane) was evaporated to dryness. An adequate amount of the corn oil was added to the dried residue in two steps. Finally unlabeled Pyranol was added. The nominal concentration of the test substance in the solution in corn oil was 111.28 mg/g (corresponding to 102.37 mg/mL). The nominal specific activity in the test substance preparation was 4.01 MBq/g (corresponding to 3.69 MBq/mL).

ANALYSIS
- Method type(s) for identification: Liquid scintillation counting
Details on in vitro test system (if applicable):
SKIN PREPARATION
- Source of skin: rat, Crl:WI (Han) (SPF); skin preparations of >2 donors were used
- Type of skin: back skin
- Preparative technique: preparations were produced from full thickness skin using a dermatome (Accu-Dermatome GA 643, Aesculap, Germany) or supplied already dermatomed (BIOPREDIC International,Saint-Grégoire, France)
- Thickness of skin: 260 – 390 µm
- Membrane integrity check: Only skin with a TEER (impedance value) above 1 kOhm and a TEWL below 15 g/m2h were used.
- Storage conditions: Maximum storage time of 3 days in a refrigerator or 12 months at -20°C.

PRINCIPLES OF ASSAY
- Diffusion cell: Modified Franz cell (Laboratory Glass Apparatus Inc, U.S.A. or BASF SE)
- Receptor fluid: tap water
- Solubility of test substance in receptor fluid:
- Static system
- Test temperature: 32 ± 1°C
- Occlusion: Since the test-substance was volatile, the donor chamber was covered with a charcoal filter after application. The openings of the donor chambers were covered with Fixomull® Stretch adhesive fleece (semi-occlusive conditions).

Results and discussion

Any other information on results incl. tables

Mean recoveries and kinetic parameters of absorption

dose group / species

 

high dose / rat
(pure Pyranol)

low dose / rat
(solution in corn oil)1

target concentration

[mg/mL]

950

100

target dose level
of test substance

[µg/cm²]

9500

1000

mean actual dose level
of test substance

[µg/cm²]

8500

902

recovery

[% of applied dose]

non-absorbed dose
(donor chamber washing,
skin washes, tape strip sample 1, charcoal filter)

83.54

55.48

absorbed dose
(receptor fluid,
receptor chamber washing)

14.80

36.27

dose associated to skin
(skin, tape strip sample 2)

3.12

7.51

dermal absorption estimate
(sum absorbed dose +
dose associated to skin)

 

17.92

43.78

total recovery

101.47

99.25

absorption kinetics

 

 

Kp

[*10-5cm/h]

13.38

37.10

absorption rate

[µg / (cm²*h)]

127.08

37.99

lag time

[ h ]

1.27

0.42

1 Mean value based on cells 6, 7 and 8. Two cells (cell 9 and 10) had recoveries of 76.79 and 62.19% of dose and were assessed to be invalid.

Taken together, the data clearly demonstrate that Pyranol is absorbed through rat skin under the test conditions used.

Applicant's summary and conclusion