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Toxicological information

Basic toxicokinetics

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Administrative data

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

Data source

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

Materials and methods

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

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

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
Doses / concentrations
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.

Results and discussion

Main ADME resultsopen allclose all
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.

Toxicokinetic / pharmacokinetic studies

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.
Toxicokinetic parametersopen allclose all
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

Metabolite characterisation studies

Metabolites identified:
yes
Details on metabolites:
It was deduced that the substance was conjugated based on the molecular weight.

Applicant's summary and conclusion

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.