Registration Dossier

Toxicological information

Dermal absorption

Currently viewing:

Administrative data

Endpoint:
dermal absorption in vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2013-2014
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail
Cross-reference
Reason / purpose:
reference to same study
Reference
Endpoint:
basic toxicokinetics in vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2013-2014
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail
Objective of study:
absorption
distribution
excretion
Principles of method if other than guideline:
Principle of test:
- Disposition of β-OTNE, was investigated following a single oral (20 mg/kg bw) dose of [14C]β-OTNE to male Fisher rats.
- Short description of test conditions:
Oral administration: Single radiolabeled oral doses were administered to male rats, by intra-gastric gavage, in a dose volume of 5 mL/kg bw via a syringe. Following administration, animals were returned to metabolism cages. Groups of 4 animals were sacrificed at 4, 8, 24 and 48 h following administration. A group of bile duct cannulated male rats were also given 20 mg/kg as above and sacrificed after 48 h following administration.
- Parameters analysed / observed:
Disposition of radioactivity at 4, 8, 24 or 48h following oral administration and 24, 48 or 96h after dermal application (tissues, organs, feces, urine, bile)
Blood or tissue concentration versus time profiles
Blood and tissue toxicokinetic parameters (T1/2, Mean Residence Time, AUC, Terminal elimination rate constant, Tmax, Cmax)
Excretion of radioactivity following administration
GLP compliance:
not specified
Radiolabelling:
yes
Remarks:
[14C]β-OTNE
Species:
rat
Strain:
Fischer 344
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Taconic Farms (Germantown, NY), Bile duct cannulated male Fisher rats were obtained from Hilltop Labs (Scottsdale, PA)
- Age at initiation: 8-12 weeks
- Housing: individual all glass metabolism cages
- Diet (e.g. ad libitum): Purina rodent chow (5002) ad libitum
- Water (e.g. ad libitum): tap water ad libitum
- Acclimation period: 3 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 17.7–26.1
- Humidity (%): 30-70
- Photoperiod (hrs dark / hrs light): 12/12
Route of administration:
oral: gavage
Vehicle:
other: 0.9%Saline:Alkamulus EL-620/L (9:1)
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
Dose formulations contained [14C]β-OTNE (5 µCi/rat), an appropriate amount of non-radiolabeled OTNE in 0.9% saline:Alkamulus EL-620/L (9:1). Oral doses were administered by intra-gastric gavage in a dose volume of 5 mL/kg via a syringe equipped with a 16 gauge ball tipped gavage needle.

Duration and frequency of treatment / exposure:
Single doses were administered
Dose / conc.:
20 mg/kg bw (total dose)
No. of animals per sex per dose:
4 males per dose
Control animals:
no
Details on study design:
- Dose selection rationale: An oral dose of 20 mg/kg bw was selected based on the information available in the literature (ECHA registered substance database, 2013)
Details on dosing and sampling:
TOXICOKINETIC / PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: urine, faeces, blood, cage washes, bile, skin (ears), dose site skin (dermal groups only), spleen, liver, kidney, brain, heart, lung, pancreas, thymus, testes, bladder, muscle (abdominal and hind leg), adipose (perirenal and epididymal), and stomach, cecum, large intestine, and small intestine (all with contents)
- Time and frequency of sampling: urine and feces were collected separately into flasks cooled over dry ice at 0–4, 4–8, 8–24, 24–48, 48–72, 72–96 h intervals. In the bile collection group, bile, urine and feces were collected separately into flasks cooled over dry ice at 0–4, 4–8, 8–24, and 24–48 h intervals. Blood was sampled at the end of the study.

Statistics:
Non-compartmental analysis of blood or tissue concentration versus time data was conducted using Phoenix WinNonlin software, version 6.3 (Pharsight Corporation, Cary, NC). Individual animal data was modeled. Parameters estimated were: Lambda-z, rate constant of elimination; t1/2, half-life of elimination; Cmax, maximum concentration; Tmax, time at which the maximum concentration was achieved; AUC(0–t), area under the blood concentration versus time curve to last time point; AUC(0–1), area under the blood concentration versus time curve to infinity; AUC(0–1)/D, dose-adjusted area under the blood concentration versus time curve to infinity.
Type:
absorption
Results:
b-OTNE was well-absorbed after a single oral administration of 20 mg/kg bw [14C]β-OTNE in male rats. High fecal excretion was observed, due to excretion via bile. At least 86% of a 20 mg/kg bw oral dose was absorbed following administration.
Type:
distribution
Results:
Tissue/blood ratios (TBR) were highest in bladder (31±34), pancreas (11±4.6), liver (8.8±1.0), kidney (8.1±1.2), adipose (5.4±3.4), muscle (2±3.2) and spleen (2.6±1.2). AUC(0–48h) values were highest in the bladder, liver, kidney and pancreas.
Type:
excretion
Results:
28% and 39% of the dose was recovered in urine and feces, respectively, and 73% of a 20 mg/kg bw dose was excreted in bile within 48 h post-administration.
Details on absorption:
Following oral administration of 20 mg/kg bw in male Fisher rats, [14C]β-OTNE was excreted mainly via urine and feces. The total dose excreted in urine 48 h post administration was 28% with the majority excreted within 24 h (25%) post-administration suggesting rapid urinary excretion of [14C]β-OTNE following oral administration. However, fecal excretion continued through 48 h postadministration with 39% excreted by 48 h while the levels of radioactivity in the GI tract contents decreased slowly, suggesting a long residence time of OTNE in the gut. In bile duct cannulated rats, about 73% of a 20 mg/kg bw was eliminated in bile within 48 h post administration while the excretion in urine and feces decreased to 12.8% and 2.8%, respectively, from 29% and 39% observed for intact animals. These data supports that the high fecal excretion observed following oral administration was not due to poor absorption but excretion via bile; at least 86% (73%+12.8%) of a 20 mg/kg bw oral dose of [14C]β-OTNE was absorbed following administration in male rats. Additionally, about 80% of the dose excreted in bile was excreted within 4 h suggesting rapid absorption.
Details on distribution in tissues:
In tissues: The concentration of radioactive equivalents in tissues 4, 8, 24, and 48 h following oral administration in (excluding digestive tract tissues) reached a maximum at 8 h post dosing; tissue/blood ratios (TBR) were highest in bladder (31±34), pancreas (11±4.6), liver (8.8±1.0), kidney (8.1±1.2), adipose (5.4±3.4), muscle (2±3.2) and spleen (2.6±1.2). The overall half-life was 34.3 hours in blood and most tissues. AUC(0–48h) values were highest in the bladder, liver, kidney and pancreas.
Details on excretion:
Following an oral administration of 20 mg/kg bw in bile duct cannulated male rats, 73% of the dose was recovered in bile 48 h post dosing. The dose recovered in urine and feces 48 h post dosing was 12.8% and 2.8%, respectively.
Key result
Test no.:
#1
Toxicokinetic parameters:
half-life 1st: Blood: 34h, Adipose Tissue: 30h, Bladder: 8.7h, Brain: 25h, Heart: 24h, Kidney: 25h, Liver: 35h, Lung: 27h, Muscle: 27h, Pancreas: 19h, Skin: 22h, Spleen: 17h, Testes: 20h, Thymus: 24h
Key result
Test no.:
#1
Toxicokinetic parameters:
Tmax: Blood: 20h, Adipose Tissue: 13h, Bladder: 14h, Brain: 19h, Heart: 17h, Kidney: 17h, Liver: 19h, Lung: 19h, Muscle: 15h, Pancreas: 16h, Skin: 16h, Spleen: 14h, Testes: 17h, Thymus: 17h
Key result
Test no.:
#1
Toxicokinetic parameters:
AUC: Blood: 26, Adipose Tissue: 71, Bladder: 521, Brain: 3.8, Heart: 19, Kidney: 182, Liver: 217, Lung: 25, Muscle: 34, Pancreas: 194, Skin: 17, Spleen: 45, Testes: 11, Thymus: 13
Remarks:
µg-eq.h/g
Metabolites identified:
yes
Details on metabolites:
It was deduced that the substance was conjugated based on the molecular weight.
Conclusions:
The data indicate that β-OTNE was well-absorbed following a single oral administration of 20 mg/kg bw [14C]β-OTNE in male rats. The reported oral absorption level of 86% is considered valid for use in further risk assessment for this substance and is based on radiolabel. the substance is fully metabolised and the key metabolite is the conjugated counterpart of OTNE. The DT50 is considered to be 34.3 hours also based on radiolabel.
Executive summary:

Disposition of β-OTNE, was investigated following a single oral (20 mg/kg bw) dose of [14C] β-OTNE to male Fisher rats. The study was rated Klimisch 2, since the study was not conducted according to a guideline (not available), but the study design is documented well and the results are presented clearly. Single radiolabeled oral doses were administered to male rats, by intra-gastric gavage, in a dose volume of 5 mL/kg bw via a syringe. Following administration, animals were returned to metabolism cages. Groups of 4 animals were sacrificed at 4, 8, 24 and 48 h following administration. A group of bile duct cannulated male rats were also given 20 mg/kg bw as above and sacrificed after 48 h following administration.

Disposition of radioactivity was measured at 4, 8, 24 or 48h following oral administration (tissues, organs, feces, urine, bile). Blood and tissue toxicokinetic parameters (T1/2, Mean Residence Time, AUC, Terminal elimination rate constant, Tmax, Cmax) were determined, as well as excretion of radioactivity following administration. The data indicate that the substance was well-absorbed following a single oral administration of 20 mg/kg bw [14C] β-OTNE in male rats. At least 86% of a 20 mg/kg bw oral dose was absorbed. b-OTNE was distributed to tissues, with bladder, pancreas, liver, adipose, and kidney showing the highest exposure to the test substance. Excretion of the test substance was mainly via urine and feces following both routes of administration. Biliary excretion and enterohepatic recirculation contributed to the high and prolonged excretion in feces. The reported oral absorption level of 86%, is considered valid for use in further risk assessment for this substance. The substance is extensively metabolised because no beta-OTNE could be detected, the glucuronic conjugated is one of the key metabolites. The DT50 for OTNE based on radiolable is 34.3 hours: 1.43 days.

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
2014
Report Date:
2014

Materials and methods

Principles of method if other than guideline:
Principle of test method:
- Disposition of radioactivity was determined following a single application of 55 or 550 mg/kg bw [14C]β-OTNE to covered or uncovered dose sites in male Fisher rats.
- Short description of test conditions:
Dermal administration: Male rats were surgically fitted with indwelling jugular vein cannulae at the study laboratory. Single dermal doses of 55 or 550 mg/kg radiolabeled OTNE were applied to a 3x4 cm clipped area on the back of the animal in a dose volume of 1 mL/kg bw. Exposure was performed both with and without occlusion to protect from grooming. All animals were returned to metabolism cages following dosing. Groups of 4 animals were sacrificed at 24, 48, and 96 h following application.
- Parameters analysed / observed:
Disposition of radioactivity at 24, 48 or 96h after dermal application (tissues, organs, feces, urine, bile)
Blood or tissue concentration versus time profiles
Blood and tissue toxicokinetic parameters (T1/2, Mean Residence Time, AUC, Terminal elimination rate constant, Tmax, Cmax)
Excretion of radioactivity following administration
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Type:
Constituent
Test material form:
liquid
Radiolabelling:
yes
Remarks:
[14C]β-OTNE

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Taconic Farms (Germantown, NY), Bile duct cannulated male Fisher rats were obtained
from Hilltop Labs (Scottsdale, PA)
- Age at initiation: 8-12 weeks
- Housing: individual all glass metabolism cages
- Diet (e.g. ad libitum): Purina rodent chow (5002) ad libitum
- Water (e.g. ad libitum): tap water ad libitum
- Acclimation period: 3 days
ENVIRONMENTAL CONDITIONS
- Temperature (°C): 17.7–26.1
- Humidity (%): 30-70
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Type of coverage:
other: open or site protected from ingestion (semi-occlusive)
Vehicle:
ethanol
Duration of exposure:
PREPARATION OF DOSING SOLUTIONS:
dose formulations contained [14C]β-OTNE (10 µCi/rat) and an appropriate amount of non-radiolabeled OTNE in ethanol in a dose volume of 1 mL/kg bw.
Doses:
- Nominal doses: 55 mg/kg bw and 550 mg/kg/bw
- Dose volume: 1 mL/kg bw
- Rationale for dose selection: dermal doses selected were approximately 0.01 and 0.1% of LD50 values reported in rodents
No. of animals per group:
4 animals per dose
Control animals:
no
Details on study design:
DOSE PREPARATION
- Method for preparation of dose suspensions: dose formulations were prepared to contain [14C]β-OTNE (10 µCi/rat) and an appropriate amount of nonradiolabeled OTNE in ethanol in a dose volume of 1 mL/kg, method was not further specified.

TEST SITE
- Preparation of test site: on the day of dosing, the fur was clipped from the animal’s back and the clipped area on each animal was examined for nicks.
- Area of exposure: the outline of the dosing area of a 3 x 4 cm was inscribed on the back of the animal with a marker and defined as the dose area.
- Type of cover / wrap if used: a protective foam appliance with a non-occlusive cotton cloth cover and an aluminum grate
- Other: single dermal doses of 55 or 550 mg/kg bw were applied to the marked area using a syringe fitted with an 18-gauge gavage needle and spread evenly on the marked dose site; dose formulations contained [14C]β-OTNE (10 µCi/ rat) and an appropriate amount of non-radiolabeled OTNE in ethanol in a dose volume of 1 mL/kg bw. All animals were returned to metabolism cages following dosing. Groups of 4 animals were sacrificed at 24, 48, and 96 h following application.

SITE PROTECTION / USE OF RESTRAINERS FOR PREVENTING INGESTION: yes: In groups protected from oral grooming, prior to dosing animals, a protective foam appliance was glued onto each rat’s back using tape and medical adhesive (3M, St. Paul, MN). Following application of the dose, a non-occlusive cotton cloth cover was fitted over the appliance and an aluminum grate was placed over the entire appliance to secure the appliance to the rat and to protect the appliance from being chewed.

REMOVAL OF TEST SUBSTANCE
- Removal of protecting device: prior to blood collection, the protective appliance was removed.
- Washing procedures and type of cleansing agent: the dose site skin was washed with 8 gauzes moistened with soapy water, and 4 moistened with water, and rinsates and gauzes were collected.
- Time after start of exposure: 96 h

SAMPLE COLLECTION
- Collection of blood: at 6, 12, 24, 48, 72, or 96 h
- Collection of urine and faeces: 0–4, 4–8, 8–24 h in main study rats, 24–48, 48–72, 72–96 h in the bile collection group, bile, urine and feces were collected separately at 0–4, 4–8, 8–24, and 24–48 h intervals.
- Terminal procedure: at the end of all studies (except the bile duct cannulated group), the animals were euthanized by asphyxiation with CO2 and blood was collected via cardiac puncture into a heparinized syringe.
- Analysis of organs/tissues: skin (ears), dose site skin (dermal groups only), spleen, liver, kidney, brain, heart, lung, pancreas, thymus, testes, bladder, muscle (abdominal and hind leg), adipose (perirenal and epididymal), and stomach, cecum, large intestine, and small intestine (all with contents)

SAMPLE PREPARATION
- Storage procedure: urine and feces were collected separately into flasks cooled over dry ice, in the bile collection group, bile, urine and feces were collected separately into flasks cooled over dry ice. All samples collected were stored at -20°C until analyzed.
- preparation: Blood and tissues from all studies were aliquoted in triplicate. All tissues were minced before sampling ca. 100 mg aliquots for further processing. Tissues, skin, and carcass were digested in 2N ethanolic NaOH prior to analysis. Darker samples such as feces, blood, kidney, spleen, heart, and lungs were bleached. Duplicate aliquots of urine, and triplicate aliquots of cage rinse, feces, skin wash, blood, and tissue and carcass digests were added directly to vials containing Ultima Gold scintillation cocktail and analyzed for radioactivity content by liquid scintillation spectroscopy (LSS) using a Packard 1900CA Tri-Carb Liquid Scintillation Analyzer (Perkin Elmer, Waltham, MA).

ANALYSIS
- Method type(s) for identification: liquid scintillation counting

Results and discussion

Signs and symptoms of toxicity:
no effects
Dermal irritation:
not specified
Absorption in different matrices:
In general, the concentration of radioactive equivalents in tissues (excluding digestive tract tissues) reached a maximum by 24–48 h and declined by 96 h post dosing.
The concentrations were highest in kidney, adipose, pancreas, liver, bladder, and non-dose site skin. The percent dose recovered in tissues 96 h post application to the covered dose site was 0.37% and 0.60% for 55 and 550 mg/kg bw, respectively. Compared to animals with covered dose sites, the percent dose in tissues was increased slightly in groups with uncovered dose sites with 0.57% and 1% of the applied dose recovered at 96 h post application. For further details please refer to the tables in the "other information on results" section.

Total recovery:
- Total recovery (% dose recovered at 96 h):
Uncovered 55 mg/kg bw: 34 +/- 2.8%
Uncovered 550 mg/kg bw: 80 +/- 7.4%
Covered 55 mg/kg bw: 74 +/- 2.8%
Covered 550 mg/kg bw: 90 +/-1.6%
Percutaneous absorptionopen allclose all
Time point:
96 h
Dose:
55 mg/kg bw (covered)
Parameter:
percentage
Absorption:
14 %
Key result
Time point:
96 h
Dose:
550 mg/kg bw (covered)
Parameter:
percentage
Absorption:
15 %
Time point:
96 h
Dose:
55 mg/kg bw (uncovered)
Parameter:
percentage
Absorption:
33 %
Remarks on result:
other: significant absorption due to oral grooming
Time point:
96 h
Dose:
550 mg/kg bw (uncovered)
Parameter:
percentage
Absorption:
72 %
Remarks on result:
other: significant absorption due to oral grooming

Any other information on results incl. tables

Table 1. Disposition of radioactivity following a single dermal application of 55 or 550 mg/kg bw [14C]b-OTNE to male Fisher rats and sacrificed 24, 48 or 96 h following application.

Covered

Uncovered

55 mg/kg

550 mg/kg

55 mg/kg

550 mg/kg

Sample

24 h

48 h

96 h

24 h

48 h

96 h

24 h

48 h

96 h

24 h

48 h

96 h

Unabsorbed dose

60±4.2

57±6.8

58±2.8

61±3.7

60±4.5

59±3.9

5.3±1.8

1.6±0.7

0.5±0.2

20±7.3

4.6±2.1

0.9±1.0

Dose site skin

9.2±1.6

4.4±1.10

3.1±0.22

18±4.6

16±2.0

11±2.8

8.2±3.1

2.5±0.79

0.72±0.31

8.6±3.9

2.6±1.2

1.4±0.54

Absorbed dose

8.9±1.0

13±1.5

14±1.9

10±1.1

14±1.2

15±9.9

36±12.2

35±6.0

33±2.4

54±12.3

68±6.1

72±6.9

Urineb

1.2±0.3

3.0±0.6

5.1±0.6

0.9±0.2

3.9±0.4

8.1±1.2

6.3±2.6

11±1.8

14±1.2

9.5±2.8

29±3.7

36±3.6

Feces

0.6±0.3

2.0±0.4

4.0±0.3

0.2±0.1

1.4±0.7

5.3±0.3

2.9±1.6

7.4±1.4

12±2.6

1.9±0.9

11±2.8

22±5.9

Tissues

0.6±0.1

0.8±0.5

0.4±0.1

0.6±0.1

0.8±0.2

0.6±0.2

1.6±0.5

1.1±0.3

0.6±0.2

1.9±0.3

1.9±0.4

1.0±0.2

GI tractc

4.3±0.7

4.3±0.7

3.1±0.6

2.7±0.2

3.5±0.4

2.5±0.8

16±4.0

12±2.2

4.6±0.2

9.9±2.5

8.3±0.9

5.1±0.8

Carcass

2.3±0.1

2.5±0.9

1.7±0.5

5.8±1.2

4.1±1.3

2.9±1.2

10±4.0

3.9±0.6

1.5±0.2

31±8.6

18±1.4

7.3±3.3

Total

78±6.2

74±9.0

74±2.8

89±2.1

91±2.1

90±1.6

50±11

39±4.9

34±2.8

84±2.0

80±3.2

80±7.4

 

Table 2. Tissue distribution of radioactivity following a single dermal application of 55 and 550 mg/kg bw [14C]b-OTNE to covered dose sites in male Fisher rats and sacrificed 24, 48 or 96 h following application.

Concentration (ng Equivalents/g Tissue)

55 mg/kg

550 mg/kg

Tissue

24 h

48 h

96 h

24 h

48 h

96 h

Blood

246±113

258±68

191±23

2924±1367

5374±1689

2349±1618

Adipose

1842±924

1472±555

963±623

21599±3881

25116±5679

19875±8054

Muscle

208±90

657±817

188±134

1984±532

4335±2491

2883±1806

Skin

4217±1536

3127±684

2405±1185

23017±5333

28747±6047

27947±9663

Bladder

3477±3308

2403±1332

2104±1370

8466±2739

23919±16051

10225±3396

Testes

200±81

136±32

92±14

1862±419

2084±512

1592±492

Kidney

2697±434

1533±279

1132±229

32238±2309

28923±7053

18418±1999

Spleen

360±100

508±377

440±262

3595±1531

4404±2247

3451±1921

Liver

1818±262

1874±426

1747±250

14889±3572

19002±4625

15296±2055

Lung

638±121

465±96

347±75

6068±956

6635±1296

4896±1561

Heart

356±75

283±76

247±70

3734±484

4178±1093

3049±902

Brain

128±28

82±18

63±13

1771±122

1717±450

1242±316

Thymus

294±115

312±84

219±45

9031±564

9675±2885

4963±1043

Pancreas

1816±708

2568±1775

1046±370

21942±3681

18080±2458

17389±12555

% Dose in Tissues

0.56±0.14

0.76±0.50

0.37±0.14

0.55±0.09

0.83±0.16

0.60±0.24

 

Table 3. Tissue distribution of radioactivity in male Fisher rats following a single dermal application of 55 and 550 mg/kg bw [14C]b-OTNE to uncovered dose sites and sacrificed 24, 48 or 96 h following application.

Concentration (ng Equivalents/g Tissue)

55 mg/kg

550 mg/kg

Tissue

24 h

48 h

96 h

24 h

48 h

96 h

Blood

1021±468

739±70

424±58

10950±2092

11546±2226

7483±1009

Adipose

3803±1468

1660±307

784±408

39493±4907

57538±12802

29037±8190

Muscle

621±305

555±438

360±175

10441±240

7477±3033

3605±707

Skin

25997±11358

4270±477

1729±155

311904±21496

352727±76805

100693±38394

Bladder

6080±230

3990±1738

1515±880

64338±21769

50426±57568

25114±26261

Testes

472±164

303±29

129±14

7987±1323

5333±598

2608±759

Kidney

7443±2449

3136±740

1385±129

103291±44534

65017±3982

32110±6845

Spleen

1407±722

777±363

384±28

19961±15094

9629±1536

6039±787

Liver

5910±1916

4909±1111

2730±97

44378±6188

48522±3416

36618±6926

Lung

1747±580

595±160

460±59

19758±2021

15843±1749

8381±2615

Heart

911±289

665±115

345±47

14112±4469

9640±1048

6168±2034

Brain

324±105

149±17

89±6

4827±216

3306±453

1418±513

Thymus

958±354

535±70

342±107

27550±8948

18755±5995

6146±2715

Pancreas

5076±3388

1863±1054

833±158

33364±3211

34451±5020

12218±3613

% Dose in Tissues

1.62±0.50

1.05±0.31

0.57±0.19

1.90±0.35

1.95±0.35

1.00±0.17

 

Effects of grooming and volatilisation

The absorption of b-OTNE was low and was not dose-dependent (14% and 15%, for 55 and 550 mg/kg, respectively). When the dose site was uncovered, the total dose absorbed increased suggesting significant oral grooming (33% and 72%, for 55 and 550 mg/kg, respectively). In addition, the total dose recovered was lower when the dose site was uncovered compared to covered dose sites suggesting rapid volatilization of the dose from the uncovered site.

Excretion after dermal absorption

Excretion following dermal dosing was mainly via urine and feces. The dose excreted in urine 96 h post application for 55 and 550 mg/kg bw, respectively, was ca. 5% and 8% in covered groups and ca.14% and 36% in the uncovered groups. The dose excreted in feces 96 h post application was slightly lower than in urine and was ca. 4% and ca. 5% in covered groups and ca. 12% and ca. 22% in the uncovered groups, for 55 and 550 mg/kg bw, respectively.

Applicant's summary and conclusion

Conclusions:
The percutaneous absorption of OTNE (using radiolabel) was determined to be 14% and 15% after semi-occlusive dermal application of 55 and 550 mg/kg bw, respectively. The reported percutaneous absorption level of 15% is the most conservative value and can be used for risk assessment purposes. The DT50 in at the low and high dose is 70 and 40 hours, respectively.
Executive summary:

Disposition of β-OTNE was investigated following a single dermal (55 or 550 mg/kg) dose of [14C] β-OTNE to male Fisher rats. The study was rated Klimisch 2, since the study was not conducted according to a guideline (not available), but the study design is documented well and the results are presented clearly. Prior to inclusion in the study, male rats were surgically fitted with indwelling jugular vein cannulae at the study laboratory. On the day of dosing, the fur was clipped from the animal’s back and the clipped area on each animal was examined for nicks. The outline of the dosing area of a 3 x 4 cm was inscribed on the back of the animal with a marker and defined as the dose area. Single dermal doses of 55 or 550 mg/kg bw were applied to the marked area in a dose volume of 1 mL/kg. In groups protected from oral grooming, prior to dosing animals, a protective foam appliance was glued onto each rat’s back using tape and medical adhesive. Following application of the dose, a non-occlusive cotton cloth cover was fitted over the appliance and an aluminium grate was placed over the entire appliance to secure the appliance to the rat and to protect the appliance from being chewed. All animals were returned to metabolism cages following dosing. Groups of 4 animals were sacrificed at 24, 48, and 96 h following application. The absorption of β-OTNE was low and was not dose-dependent (14% and 15%, for 55 and 550 mg/kg, respectively). When the dose site was uncovered, the total dose absorbed increased suggesting significant oral grooming (33% and 72%, for 55 and 550 mg/kg bw, respectively). In addition, the total dose recovered was lower when the dose site was uncovered compared to covered dose sites suggesting rapid volatilization of the dose from the uncovered site. b-OTNE was distributed to tissues with bladder, pancreas, liver, adipose, and kidney showing the highest exposure to the test substance. Excretion of the substance was mainly via urine and faeces following both routes of administration. The dose excreted in urine 96 h post application for 55 and 550 mg/kg bw, respectively, was ca. 5% and 8% in covered groups and ca.14% and 36% in the uncovered groups. The dose excreted in faeces 96 h post application was slightly lower than in urine and was ca. 4% and ca. 5% in covered groups and ca. 12% and ca. 22% in the uncovered groups, for 55 and 550 mg/kg bw, respectively. Biliary excretion and enterohepatic recirculation contributed to the high and prolonged excretion of the test substance in faeces. The higher fecal and urinary excretion levels in the uncovered group are also suggesting a significant effect of oral intake due to grooming. The results for this study indicate that a covered dermal exposure provides a reliable estimate of the percutaneous absorption of the test substance, as it prevents oral intake due to grooming, and rapid volatilisation of the substance. The reported percutaneous absorption level of 15% is the most conservative value and can be used for risk assessment purposes. The The DT50 in at the low and high dose is 70 and 40 hours, respectively.