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Link to relevant study record(s)

Reference
Endpoint:
basic toxicokinetics
Type of information:
experimental study
Adequacy of study:
key study
Study period:
18.05.2006 - 10.07.2007
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Objective of study:
toxicokinetics
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 417 (Toxicokinetics)
Version / remarks:
The study was based on partially fulfilling the requirements of the guideline
Principles of method if other than guideline:
The objective of this study was: To determine whether the test article is absorbed following oral administration.
GLP compliance:
yes (incl. certificate)
Radiolabelling:
yes
Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: in-house, animals were received at the research laboratory
- Age at study initiation: males: ca. 6-7 weeks; females ca. 8-9 weeks
- Weight at study initiation: males: 187 - 225 g, females: 186-229 g
- Fasting period before study: no
- Housing: housed individually in glass metabolism cages (Metabowls)
- Individual metabolism cages: yes
- Diet: VRFI diet, ad libitum
- Water: from local water supply, ad libitum
- Acclimation period: at least 5 days prior to dosing

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 +/- 2
- Humidity (%): 55 +/- 15
- Air changes (per hr): approx. 15
- Photoperiod: 12 hrs dark / 12 hrs light

IN-LIFE DATES: 31.05. - 06.09.2006
Route of administration:
oral: gavage
Vehicle:
other: 4 % carboxymethylcellulose and 0.2 % Tween 80
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
Dose formulations were freshly prepared for administration to groups of animals. Where required radiolabelled and non-radiolabelled test item were mixed together in ethyl acetate to achieve the desired specific activity for the dosed material. For all other dose groups, the radiolabelled test item was not radiodiluted. The solvent was removed under a stream of nitrogen and the solid material suspended in 2% (w/v) aqueous carboxymethylcellulose solution / 0.2% Tween 80, using a magnetic stirrer.
The quantity of radioactivity administered to each animal was determined from the weight of the administered formulation (based on the weight of the dosing syringe before and after dosing) and the measured concentration of radioactivity in the formulation. Further weighed portions of the dose formulation were either counted directly by LSC or dispensed into 20 or 25 mL volumetric flasks. These were made up to volume with methanol and triplicate aliquots of each solution taken for radioactivity measurement. The specific activity of the [14C]-test item in the high level formulation was calculated from the radioactivity concentration of the formulation (taking into account the specific activity of the undiluted test item) and the weight of non-radiolabelled test item in the formulation.
The nominal radioactivity contained in each dose (50 mg/kg groups) was 20 µCi per rat (200 g).

VEHICLE
- Amount of vehicle (if gavage): 10 mL/kg bw

HOMOGENEITY AND STABILITY OF TEST MATERIAL:
At least triplicate aliquots of each dose formulation were analyzed for radioactivity to confirm the homogeneity of the formulation and the actual dose level. The dose formulation were analyzed for stability of the test substance after dosing.
Duration and frequency of treatment / exposure:
All animals received a single dose via oral gavage.
Dose / conc.:
0.5 mg/kg bw/day
Remarks:
Group 1: Excretion/tissue distribution, sacrifice 168h
Dose / conc.:
50 mg/kg bw/day
Remarks:
Group 2: Excretion/tissue distribution, sacrifice 168h
Dose / conc.:
0.5 mg/kg bw/day
Remarks:
Group 3: Tissue distribution, sacrifice 6h
Dose / conc.:
50 mg/kg bw/day
Remarks:
Group 4: Tissue distribution, sacrifice 6h
No. of animals per sex per dose:
4
Control animals:
no
Positive control:
None
Details on study design:
- Dose selection rationale: Dose levels have been selected after consultation with the appropriate Regulatory Authority, the BfR, and have been set at levels which would cause no observable effects (NOEL).
Details on dosing and sampling:
PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: urine, cage wash, faeces, plasma, whole-blood, fat, muscle, brain, heart, kidney, liver, lungs, spleen, testes, ovaries, uterus, gastrointestinal tract, carcass
- Time and frequency of sampling:
urine: 0-6, 6-24, 24-48, 48-72, 72-96, 96-120, 120-144, 144-168 hrs after administration
faeces: 0-24, 24-48,48-72, 72-96, 96-120, 120-144, 144-168 hours after administration
volatiles: 0-24 hrs after the administration
all others: 168 hrs after administration
Statistics:
The mean and standard deviation were used to characterise the data, where appropriate (i.e., radioactivity measurement, concentrations, etc.). Concentrations of radioactivity in blood, plasma and tissues were calculated as µg equivalents of test item/g of sample. The total amounts of radioactivity in tissue and excreta samples were calculated as a percentage of the administered radioactivity and a 14C mass balance is presented. Individual excretion half-lives (t ½) were calculated by linear regression of time versus log concentration curves for urine and faeces.
Type:
absorption
Results:
Absorption based on values in urine, expired air and tissues was low.
Type:
distribution
Results:
After 6hrs (high and low dose level): liver > spleen > ovaries > all others; after 168 hrs (high and low dose level): ovaries > liver > fat > all others
Type:
excretion
Results:
Mainly via faeces and in a lower extend via urine and negligibly via expired air.
Details on absorption:
Absorption values in urine, expired air and tissues was low (1-3 % dose).
Details on distribution in tissues:
- 168 hours
0.5 mg/kg bw and 50 mg/kg bw test item:
Following administration of [phenyl-14C]-test item, very little of the administered radioactivity (< 1 %) was retained in the tissues at 168 hours. The highest accumulation occurred in the ovaries, liver and fat. There was less than a proportional increase in tissue concentrations of radioactivity at the high dose level.

- 6 hours
0.5 mg/kg bw test item:
Following administration of [phenyl-14C]-test item at 0.5 mg/kg bw (low level), a mean of less than 8 % administered radioactivity was retained in the tissues other than gastrointestinal tract (including contents) at 6 hours. Most of the retained radioactivity was detected in the liver (7 % dose). The highest concentrations occurred in the liver, spleen and ovaries.
50 mg/kg bw test item:
At 6 hours following administration of [phenyl-14C]-test item at 50 mg/kg bw (high level), a mean of 3 % administered radioactivity was retained in the tissues other than gastrointestinal tract and contents. Most of the retained radioactivity was detected in the liver (3 % dose). The highest concentrations occurred in the liver, spleen and ovaries.
Details on excretion:
After administration of [14C]-test item at the low and high dose levels, < 1 % dose was excreted in the urine and 93 - 96 % was excreted in the faeces. More than 77 % dose was excreted in the faeces during 0 - 24 hours after dose administration. Most of the radioactivity (>90 %) was excreted within the first 48 hours after administration.
Metabolites identified:
not measured

Description of key information

Key value for chemical safety assessment

Additional information

The excretion and tissue distribution of 14C-labeled test article has been studied after single oral doses to rats at 0.5 mg/kg and 50 mg/kg (Huntingdon, 2007). Following administration of [phenyl-14C]-test substance, most of the radioactivity (>90%) was excreted in the feces within the first 48 hours, a minimum of 77% was excreted in the feces by 24 hours. At least 93% was excreted in the feces during the course of the experiment regardless of dose level or sex. Very little of the administered radioactivity (< 1%) was retained in the tissues at 168 hours. The highest accumulation occurred in the ovaries, liver and fat. There was less than a proportional increase in tissue concentrations of radioactivity at the high dose level. The measured radioactivity in urine and expired air was minimal (1-2%). Following administration of [phenyl-14C]-test substance at 0.5 mg/kg (low level), a mean of less than 8% administered radioactivity was retained in the tissues other than gastrointestinal tract (including contents) at 6 hours. Most of the retained radioactivity was detected in the liver (7%). The highest concentrations occurred in the liver, spleen and ovaries. At 6 hours following administration of [phenyl-14C]-test substance at 50 mg/kg (high level), a mean of 3% administered radioactivity was retained in the tissues other than gastrointestinal tract and contents. Most of the retained radioactivity was detected in the liver (3%). The highest concentrations occurred in the liver, spleen and ovaries.

In conclusion, most of the test article (> 90%) is excreted in the feces within 48 hours. The absorption based on values in urine, expired air and tissues was low (1-3%). Of the remaining radioactivity, only 3% (high dose) or 8% (low dose) was found in tissue other than the gastrointestinal tract. Thus, only minimal amounts of the test article are absorbed through the gastrointestinal tract and the substance is therefore considered to be not bioavailable.

Dermal absorption is not expected due to the chemical's insolubility in water (Huntingdon, 2006) and the log Pow of 8.9 (Ciba-Geigy, 1986). This is in line with the available toxicity data after dermal exposure. In an acute dermal toxicity study (Ciba-Geigy, 1986) and in a guinea pig maximization assay (Ciba-Geigy, 1987), no indications of systemic availability after dermal application were detected. These findings indicate that the substance is not penetrating the skin and systemic availability upon dermal exposure is expected to be low. No information from acute or repeated dose toxicity studies is available, which could provide information about the systemic distribution of the test substance after inhalation. However, considering its low water solubility and log Pow of 8.9, absorption of the substance via the inhalative route is not favorable (ECHA GD 7c, 2008). In addition, the substance is characterized by a very low vapor pressure (0.000024 Pa at 25°C) and a boiling point of 414°C. Therefore, human exposure via inhalation is unlikely.

Overall conclusion: The test article is not absorbed readily during passage through the gastrointestinal tract and is excreted rapidly via the feces, as demonstrated by an in vivo toxicokintic study. Furthermore, absorption after dermal exposure and by inhalation is expected to be low based on dermal toxicity studies and the physico-chemical properties. Consequently, systemic availability of the test substance is therefore expected to be low.