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Basic toxicokinetics

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Administrative data

Endpoint:
basic toxicokinetics
Type of information:
experimental study
Adequacy of study:
key study
Study period:
12 Feb 2005 - 11 Apr 2007
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study conducted according to GLP

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2007
Report Date:
2007

Materials and methods

Objective of study:
toxicokinetics
Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 417 (Toxicokinetics)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
Landesamt für Umwelt, Wasserwirtschaft und Gewerbeaufsicht, Mainz

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Protectol PE
- Physical state: viscous, colourless liquid
- Analytical purity: > 99.9% (unlabelled; chemical, GC), 96.5% (labelled; chemical, HPLC)
- Lot/batch No.: 41183068E0 (unlabelled), 873-1012 (labelled)
- Radiochemical purity (if radiolabelling): 97.9% (Radio-HPLC)
- Specific activity (if radiolabelling): 6.7 MBq/mg
- Locations of the label (if radiolabelling): Phenyl-U-C14
- Stability under test conditions: stable
- Storage condition of test material: refrigerator
Radiolabelling:
yes
Remarks:
14C-2-phenoxyethanol

Test animals

Species:
rat
Strain:
Wistar
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Deutschland GmbH
- Age at study initiation: at least 9 weeks
- Weight at study initiation: weight was measured prior to dosing
- Housing: Type III macrolon cages during acclimatization and prior to the experiment
- Individual metabolism cages: yes
- Diet (e.g. ad libitum): Kliba lab diet, Provimi Kliba SA, Switzerland
- Water (e.g. ad libitum): tap water

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 - 24
- Humidity (%): 30 -70
- Photoperiod (hrs dark / hrs light): natural day/night rhythm with additional artificial light as required during working hours


IN-LIFE DATES: From: 06 Dec 2005 To: 28 Jun 2006

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
CMC (carboxymethyl cellulose)
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
The test substance was prepared in 0.5% CMC in double distilled water. About 10 mL/kg bw of a preparation were administered. In order to achieve the required specific activity, respective amounts of non-radiolabelled material were added to the respective amounts of stock solution of radiolabelled material and the aqueous vehicle was added and filled up to the final volume. The required quantity of radioactivity per animal was about 0.5 - 2.5 MBq.


HOMOGENEITY AND STABILITY OF TEST MATERIAL:
Verified in all experiments by HPLC.
Duration and frequency of treatment / exposure:
Experiments 1 to 4: single dose
Experiments 5 to 7: single and multiple dose (one administration of unlabelled material for 14 days and one of labelled test material on day 15)
Experiments 8 & 9: single dose
Experiments 10 & 11: single dose
Doses / concentrations
Remarks:
Doses / Concentrations:
Experiments 1 to 4: 1000, 300, 100 and 30 mg/kg bw
Experiments 5 to 7: 40 and 400 mg/kg bw as a single dose and 400 mg/kg bw each for the multiple dose
Experiments 8 & 9: 40 and 400 mg/kg bw as a single dose
Experiments 10 & 11: 40 and 400 mg/kg bw as a single dose
No. of animals per sex per dose:
Experiments 1 to 7 and 10: 4 per sex and dose
Experiments 8 & 9: 3 females per timepoint
Experiment 11: 4 females
Control animals:
no
Details on study design:
- Dose selection rationale: The doses have been selected on the basis of the results from previously performed studies on the chronic toxicity of 2-phenoxyethanol in rats.
Details on dosing and sampling:
PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
Experiments 1 to 4:
In male and female rats, kinetic parameters based on total radioactivity following a single oral dose of 14C-Protectol PE at four dose levels (1000, 300, 100 and 30mg/kg bw) were determined. Blood samples at 1, 2, 4, 8, 24h and subsequently in time intervals of 24h up to 96h were collected.

Experiments 5 to 7:
The absorption, distribution and excretion of radiolabelled products was investigated after single (40 and 400mg/kg bw) and multiple (one administration of unlabelled test item for 14 days and one of labelled test item on day 15) oral doses of 14C-Protectol PE in male and female rats. Therefore, urine after 6, 12, 24h and subsequently in time intervals of 24h up to 96h was collected. Feces were sampled in intervals of 24h up to 168h. After 168h, animals were sacrificed and the following organs and tissues (heart, liver, spleen, bone, skin, lung, ovaries/testes, carcass, muscle, kidney, brain, pancreas, uterus, adipose tissue, stomach and stomach contents, thyroid glands, adrenal glands, blood cells and plasma, gut and gut contents, bone marrow) were checked for remaining radioactivity.

Experiments 8 & 9:
In order to determine the tissue distribution of radioactivity female rats were administered a single oral dose of 40mg or 400mg 14C Protectol PE/ kg bw. The same organs and tissues as in the experiments 5 to 7 were collected at four different time points, corresponding to the maximum plasma concentration MPC, 1/2 MPC, 1/4 MPC and 1/8 MPC. For the high dose, samples were collected at 2, 4.5, 7 and 14h and for low dose at 1, 2, 3.5 and 8h.

Experiments 10 & 11:
Biliary excretion of radioactivity following a single oral dose of 400mg 14C-Protectol PE/ kg bw was determined in male and female rats. In contrast, only females were dosed once with 40mg/kg bw. Bile in 3h-intervals as well as urine and feces in 24h time intervals up to 72h were collected. After 72h stomach and stomach contents, gut and gut contents and carcass were checked for remaining radioactivity.

During the experiments 5 to 11, samples of biological material were generated following administration of 14C-Protectol PE, which are used in an investigation on the metabolism.

Results and discussion

Toxicokinetic / pharmacokinetic studies

Details on absorption:
In rats exposed to single oral doses of 1000, 300, 100 and 30 mg/kg b.w. 14C-Protectol PE (experiments 1 to 4), the maximum plasma concentration of 415.04, 82.78, 47.95 and 13.66µg Eq/g in males and 487.73, 127.26, 54.41 and 14.26µg Eq/g in females occurred 1-2h post-dosing, respectively. Afterwards, plasma levels declined to 0.22, 0.18, 0.08 and 0.04µg Eq/g in males and 0.85, 0.38, 0.14 and 0.04µg Eq/g in females at sacrifice after 96h, respectively. The initial half-lives were calculated to be 1.9–2.9h in males and 1.8–4.6h in females. Terminal half-lives were 33.1–54.1h for males and 28–60.5h for females. The calculated area under the plasma concentration time curves (AUC) were 3459, 567, 207 and 57µg Eq*h/g in males and 4596, 801, 238 and 52µg Eq*h/g in females. These calculations are based on group mean values. A comparable time course of radioactivity was found for blood as for plasma in both sexes. During the first two days post-dosing, lower concentrations of radioactivity were generally found in blood indicating that major parts of the radioactivity were in plasma and not bound to cellular blood constituents. Generally 48h post-dosing, blood/plasma ratios reached also values >1.
Increasing the dose by a factor of 33 resulted in an increase of the AUC-values by a factor of 61 in males and 88 in females. These data indicate a saturation of excretion with increasing dose. This effect is present already starting with the lowest dose of 30mg/kg b.w., since an increase of the dose to 100mg/kg b.w., corresponding to a factor of 3.3 resulted in an increase of the AUC-values by a factor of 3.6 in males and 4.6 in females (refer to Table 1).
Details on distribution in tissues:
Following a single oral dose of 14C-Protectol PE at a dose level of 400mg/kg b.w., tissue distribution was measured 2, 4.5, 7 and 14h post-dosing in females (experiment 8). At the low dose level of 40mg/kg b.w., the corresponding radioactivity measurements were performed 1, 2, 3.5 and 8h after administration in females (experiment 9). Tissue radioactivity concentrations generally declined with time parallel to plasma concentrations. Throughout the time course of the experiments, highest radioactivity concentrations were found in the GI tract, kidney, pancreas, skin and bone marrow for the high dose as well as GI tract, kidney, liver and skin for the low dose. Radioactivity levels were lowest in brain, muscle and heart for the high dose and brain, uterus, muscle and bone for the low dose. (refer to Table 2 and Table 3)
Details on excretion:
After a single oral administration of 400 mg/kg b.w. of 14C-Protectol PE (experiment 5), mean total recoveries of radioactivity were >90% in both sexes. In exhaled air, no relevant portions of the administered radioactivity were detected as CO2. After 168h the total amount of radioactivity excreted in urine was found to be 94.1% and 93.4% in males and females, respectively. Within 168h after single oral administration of 400 mg/kg b.w. to male and female rats, 2.9% and 2.0% of the administered radioactivity were excreted via feces, respectively. The time course of the amount of radioactivity found in urine and feces indicates rapid excretion.
168h post-dosing, small amounts of remaining radioactivity were found in skin (0.06–0.07%) and carcass (0.06%). Mean concentrations of radioactivity were generally below 10μg Eq/g in all organs and tissues. (Refer to Table 4)
After single oral administration of 40mg/kg b.w. (experiment 6), mean total recoveries of radioactivity were >90% in males and females and no relevant portions of the administered radioactivity were detected as CO2 in exhaled air. Within 168h after single oral administration of 40mg/kg b.w. to male and female rats, 94.0 and 92.9% of the administered radioactivity were excreted in urine, respectively. After 168h the total amount of radioactivity excreted via feces was found to be 2.2% for males and 1.9% for females. The time course of the amount of radioactivity found in urine and faeces indicates rapid excretion. Overall, the portion of radioactivity found in urine was not dose dependent, indicating comparable bioavailability at the high dose and the low dose.
168h after dosing, small amounts of remaining radioactivity were found in skin (0.06-0.08%) and carcass (0.05-0.06%). Mean concentrations of radioactivity were below 1.2µg Eq/g in all organs and tissues. (Refer to Table 5)
After daily administration of non-radiolabelled Protectol PE for 14days at a dose level of 400mg/kg b.w., and one radiolabelled administration at a dose level of 400mg/kg b.w. on day15 (experiment 7), the mean recoveries of radioactivity were >90%. Total excretion of radioactivity via urine after 168h was 96.7% and 88.5% for females. After 168h the total amount of radioactivity excreted via feces was found to be 1.4% for males and 1.7% for females. These excretion data from urine and feces indicate rapid excretion of the absorbed material.
168h post-dosing, small amounts of remaining radioactivity were found in skin (0.06%) and carcass (0.05%). Mean concentrations of radioactivity were generally below 3.5μg Eq/g in all organs and tissues. (Refer to Table 6)
For the high dose and the low dose, the portion of radioactivity found in urine was comparable, indicating a comparable bioavailability of Protectol PE at the tested dose levels. The excretion pattern after multiple dosing was not changed as compared to a single dose of Protectol PE at 400mg/kg b.w. The results of the balance and excretion experiments also show that there was no sex-difference in the excretion pattern at both dose levels.

Within 72h after administration of 14C-Protectol PE, excretion via bile was found to be about 5.6% and 4.6% of the administered radioactivity in male and female animals at the high dose level of 400mg/kg b.w. (experiment 10), respectively.
At a dose of 40mg/kg b.w. (experiment 11), excretion via bile was found to be about 3.4% of the administered radioactivity in female animals within 72h.
For both experiments, biliary excretion was highest within the first 6h post dosing and declined gradually thereafter until 72h. Assuming that the amount of radioactivity excreted represents the bioavailable portion (sum of % radioactivity in urine, cage wash, carcass and bile) of the dose, bioavailability was calculated in the bile excretion experiments to be approximately 75-98% for both dose levels. (Refer to Table 7)

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): no bioaccumulation potential based on study results
Putting all data together, it is concluded that after single oral administration, 14C-Protectol PE was rapidly and almost completely absorbed from the gastrointestinal tract. The excretion of radioactivity was very rapid and occurred mainly via the urine within 24h post dosing. Based on the amounts of radioactivity excreted via bile and urine, the high bioavailability of 14C-Protectol PE was confirmed, since the sum of radioactivity excreted via bile and urine was over 90% of the recovered radioactivity in the bile experiments. Within the current study, the bioavailability of 14C-Protectol PE was comparable at the dose of 400 and 40 mg/kg b.w. The plasma kinetics demonstrated that an increase of the dose resulted in an over proportional increase of the AUC-values, indicating a saturation of excretion with increasing dose. After absorption, radioactive material was distributed in all organs and tissues.