Registration Dossier

Administrative data

Endpoint:
basic toxicokinetics
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2006-09-11 to 2007-05-23
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study

Data source

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

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 417 (Toxicokinetics)
Version / remarks:
April 1984
Deviations:
no
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Radiolabelling:
yes

Test animals

Species:
rat
Strain:
Wistar
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: RCC Ltd, Laboratory Animal Services, CH-4414 Füllinsdorf, Switzerland
- Age at study initiation: 6-7 weeks
- Weight at study initiation: 0.157 - 0172 kg
- Fasting period before study: On the evening prior to oral dosing, food was restricted to approximately 10 gram (except for rat no. 85).
- Housing: Groups of 1-3 rats under conventional hygienic conditions in Makrolon cages with standard soft wood bedding during acclimation. The accommodation during the treatment is described in the corresponding experiment.
- Individual metabolism cages: yes
- Diet: 3433 Kliba rat maintenance diet ad libitum (PROVIMI KLIBA AG, CH-4303 Kaiseraugst, Switzerland). On the evening prior to oral dosing, food was restricted to approximately 10 gram (except for rat no. 85). Immediately after the dosing, food was again presented ad libitum.
- Water: Tap water ad libitum
- Acclimation period: 5 days to laboratory environment, including 1 day to metabolism cages.

ENVIRONMENTAL CONDITIONS
- Temperature: 20.1 - 22.7 °C
- Humidity: 47.2 - 67.8 %
- Air changes: 10-15 times/hour
- Photoperiod: 12 h light/12h darkness

In life-dates: From: 2007-05-23 to 2007-07-20

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
acetone
Details on exposure:
PREPARATION OF STOCK SOLUTIONS:
The contents of one of the delivered vials with 14C-labelled Dioctylcarbonate (nominally 2 mCi) were quantitatively transferred into a volumetric flask and made up to a volume of 5 mL with acetone (= stock solution 1). By liquid scintillation counting stock solution 1 was found to contain 3'423'933'333 dpm (57.1 MBq), corresponding to 8.38 mg 14C-labelled test item (based on the specific radioactivity of 6.81 MBq/mg).
Based on the target specific radioactivity of 67 kBq/mg for the low dose, an aliquot of 3.5 mL stock solution 1 was transferred into a volumetric flask containing 593.8 mg of the unlabelled test item and the volume was made up to 5 mL with acetone (= stock solution 2). By liquid scintillation counting stock solution 2 was found to contain 2'518'586'667 dpm (42.0 MBq), corresponding to 6.16 mg 14C-labelled test item (based on the specific radioactivity of 6.81 MBq/mg). Consequently, stock solution 2 contained a total of 600 mg Dioctylcarbonate (120 mg/mL) and the new specific radioactivity was 69.96 kBq/mg.
To the remainder of stock solution 1 (approximately 1.5 mL) the contents of a second vial with 14C-labelled Dioctylcarbonate (nominally 1 mCi) were added, and the volume was made up to 5 mL with acetone (= stock solution lb). By liquid scintillation counting stock solution lb was found to contain 2'473'875'000 dpm (41.2 MBq), corresponding to 6.05 mg 14C-labelled test item (based on the specific radioactivity of 6.81 MBq/mg).
Based on the target specific radioactivity of 6.7 kBq/mg for the high dose, stock solution lb was quantitatively transferred into a volumetric flask containing 6000.3 mg of the unlabelled test item and the volume was made up to 10 mL with acetone (= stock solution 3). By liquid scintillation counting stock solution 3 was found to contain 2'501'444'444 dpm (41.7 MBq), corresponding to 6.12 mg 14C-labelled test item (based on the specific radioactivity of 6.81 MBq/mg). Consequently, stock solution 3 contained a total of 6006.4 mg Dioctylcarbonate (600 mg/mL) and the new specific radioactivity was 6.94 kBq/mg.


PREPARATION OF ADMINISTRATION SOLUTIONS:
- Low Dose Administration Solution (Group 1 and 2): To prepare the low dose administration solution at a target concentration of 20 mg/g, stock solution 2 was quantitatively transferred into a glass vial and the solvent was completely evaporated. To the residue maize oil was added to a total weight of 30.0 g, and the test item was thoroughly re-dissolved. By liquid scintillation counting of three weighed subsamples the solution was proven to be homogenous (coefficient of variation: 1.2%), and to contain 84'167'672 dpm per gram solution (1.403 MBq/g solution), corresponding to 20.05 mg 14C-Dioctylcarbonate per gram solution (based on the specific activity of 69.96 kBq/mg). Re-analysis of the solution left over after dosing of the animais of group 1 and 2 approximately 5 weeks after the dosing confirmed this result (99.6% of the initial measurement).

- High Dose Administration Solution (Group 3 and 4): To prepare the high dose administration solution at a target concentration of 200 mg/g, stock solution 3 was quantitatively transferred into a glass vial and the solvent was completely evaporated. To the residue maize oil was added to a total weight of 30.0 g, and the test item was thoroughly re-dissolved. By liquid scintillation counting of three weighed subsamples the solution was proven to be homogenous (coefficient of variation: 0.4%), and to contain 83'603'287 dpm per gram solution (1.393 MBq/g solution), corresponding to 200.7 mg 14C-Dioctylcarbonate per gram solution (based on the specific activity of 6.94 kBq/mg). Re-analysis of the solution left over after dosing of the animais of group 3 and 4 approximately 4 weeks after the dosing confirmed this result (98.6% of the initial measurement).

ADMINISTRATION
On the evening prior to oral dosing, food was restricted to approximately 10 gram (except for one rat).Immediately prior to the dosing, the body weight of the rats was determined. Oral administration was performed by gastric intubation based on the target weight of 5 gram administration solution per kg rat body weight. The exact amount of solution administered (in mg) was determined via weighing of the application device before (with administration solution) and after administration (empty), and the amount of radioactivity administered was calculated taking into account the concentration of the corresponding application solution.


Stability of the 14C-labelled test item in the administration solutions:
The radiochemical purity of the 14C-labelled test item as determined by TLC in both administration solutions (high and low dose solution, respectively) before dosing of the first rat as well as after dosing of the last rat was found to be 98.7-99.9 % in solvent system 1, and 97.7-98.8 % in solvent system 4. This was similar to the initial radiochemical purity as determined from stock solution 1 (99.0-99.3 % in solvent system 1 and 98.1 % in solvent system 4).
Furthermore, the concentration of radioactivity in the administration solutions as proven by LSC was constant from the time of preparation up to at least 4-5 weeks after the use for dosing. Taken together, these results showed that the test item was stable in the administration solutions, and that no loss of volatile radioactivity (C02) occurred from the solution.


VEHICLE (acetone)
- Purity: analytical grade
Doses / concentrations
Remarks:
Doses / Concentrations:
Low dose level (100 mg/kg):
- Target specific activity of the test item: 67 kBq/mg (1.8 pCi/mg)
- Target radioactivity dose: 1.3 MBq/rat (8x1 07 dpm/rat)
- Target administration amount: 5 g/kg
- Target test item concentration in the administration solution: 20 mg/g

High dose level (1000 mg/kg):
- Target specific activity of the test item: 6.7 kBq/mg (0.18 pCi/mg)
- Target radioactivity dose: 1.3 MBq/rat (8x107 dpm/rat)
- Target administration amount: 5 g/kg
- Target test item concentration in the administration solution: 200 mg/g

The actually achieved mean doses were 101 ± 2.94 mg/kg (males, group 1) and 100 ± 0.830 mg/kg (females, group 2) for the low dose level, and 1001 ± 12.8 mg/kg (males, group 3) and 999 ± 7.15 mg/kg (females, group 4) for the high dose level.
No. of animals per sex per dose:
18 male and 19 female rats
Control animals:
not specified
Positive control:
Samples of stock solution 1 ( 14C-Dioctylcarbonate) and of reference solution (unlabelled Dioctylcarbonate) served as positive controls.
Details on study design:
In order to investigate whether the radioactivity present in the plasma represented unchanged 14C-labelled Dioctylcarbonate, selected plasma samples were subjected to protein precipitation and analysed by TLC (Thin Layer Chromatography).
Details on dosing and sampling:
PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: urine, faeces, blood, plasma, serum or other tissues, cage washes, bile
- Time and frequency of sampling: urine/faeces (6, 24, 48, 72, 96 hours after administration); expired air (6,24, 32, 48, 56, 72, 80, 96 hours after administration); blood/tissues/organs/carcass (after sacrifice)
- Analytical method/determination of the radioactivity: LSC (liquid scintillation counting)

Results and discussion

Toxicokinetic / pharmacokinetic studies

Details on distribution in tissues:
Tissue and organ concentrations of radioactivity at 96 h hours after the oral administration of 14C-Dioctylcarbonate in males and females were similar. In both genders, the concentrations after the high dose were about 7-16-fold higher than after the low dose, overall approximately reflecting the 10-fold increase of the dose. An exception is the comparatively high liver concentration of 55.5 µg-eq/g in one male dosed at 1000 mg/kg, which was 3.5-fold higher than the value in the female dosed at 1000 mg/kg, and 22fold higher than the value in another male dosed at 100 mg/kg.
Details on excretion:
In summary, balances and excretion patterns of radioactivity were very similar in males and females, and at both dose levels. In all four cases, the balances were incomplete (total recoveries of 69-87 %), indicating that some loss of volatile radioactivity (C02) occurred. As any C02 generated in vivo was efficiently trapped by a system of two to three serial volatile traps, it is assumed that radioactive CO2 escaped from the collected samples (faeces, urine, tissues/organs and/or carcass) during further processing.
Radioactivity concentrations in the urine samples collected from 6 to 24 hours after the administration were as high as 16.5 µg-eq/mL after the low dose and 167 µg-eq/ml after the high dose. This by far exceeds the water solubility of unchanged Dioctylcarbonate (<=0.1 µg-eq/mL), strongly suggesting that the radioactivity present in the urine at least for the very most part also represented dissolved carbon dioxide (CO2[aq]) and/or its reaction products carbonic acid (H2CO3[aq]) and hydrogen carbonate (HCO3[aq]).

Metabolite characterisation studies

Metabolites identified:
no

Any other information on results incl. tables

Kinetic of radioactivity in blood, plasma and the sexual organs:

In summary, AUC(0 -96 h) values of blood, testes, epididymes, ovaries and uterus were similar to the AUC(0 -96h) values of plasma, indicating that no accumulation of radioactivity in these organs occurred. Half-lives in blood, testes, epididymes, ovaries and uterus (35-105 hours) however tended to be higher than in plasma (25-35 hours). AUC(0 -96h) values after the high dose were about 8-fold (males) and 10-fold (females) higher than after the low dose, clearly reflecting the 10-fold increase of the dose. AUC(0 -96h) values of blood and plasma in the males tended to be slightly higher than in the females.

Analysis of radioactivity in plasma:

In total, 62-100% of the radioactivity present in the plasma samples was recovered, indicating variable loss of volatile radioactivity (C02) accounting for up to 38%.

Applicant's summary and conclusion