Registration Dossier

Administrative data

Endpoint:
basic toxicokinetics
Type of information:
experimental study
Adequacy of study:
disregarded due to major methodological deficiencies
Study period:
November 2011 - June 2012
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
other: The study has some deviations and not all information to judge the validity is available, the information in the report is incomplete

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2012
Report Date:
2012

Materials and methods

Objective of study:
toxicokinetics
Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 417 (Toxicokinetics)
Principles of method if other than guideline:
The study has many deviations and the information in the report is incomplete.
- Study reporting is of poor quality leaving many questions what exactly has been done, number of animals, doses?
- No information on the vehicle that was used
- Metabolites are not identified, nu justification is provided
- The substance was not radiolabellled, no justification is provided
- Only summary tables provided. Tables with individual data should be included.
- Mass balance information is lacking.
- There is no information whether animals were fasted before dosing.
- The statements in the report regarding cumulative excretion makes no sense, as these are based on summation of concentrations rather than total mass. Also the statement on the existence of enterohepatic cycling is wrong.
- The laboratory has no GLP accreditation
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Name: α,α,α',α'-tetramethyl-m-xylene-α,α'-diol
Lot No.: 101155
odourless white solid
Radiolabelling:
no

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male

Administration / exposure

Route of administration:
other: IV and oral
Vehicle:
not specified
Duration and frequency of treatment / exposure:
This study contained three parts, including toxicokinetics study by acute intravenous administration, toxicokinetics study by acute oral administration and toxicokinetics study by 14-day repeated dose oral administration.
Doses / concentrations
Remarks:
Doses / Concentrations:
In toxicokinetics studies, rats were treated with 1 mg/kg or (10? both are mentioned in the report) by acute intravenous administration,10, 50 and 100 mg/kg test item by acute oral administration, and 50 mg/kg test itemby 14-day repeated dose oral administration, respectively.
No. of animals per sex per dose:
Unclear: this study reporting is of poor quality leaving many questions what exactly has been done and what the number of animals was per group.
The summary of the report does not match with the method section of the report.

Control animals:
yes

Results and discussion

Any other information on results incl. tables

Abstract from study report:

Results of acute oral administration metabolism study were given below.

Feces were the main excretion pathway for the test item. The test item was removed more than 98% of the cumulative amount at 24h and eliminated almost all at 48h. The test item was removed more than 98% of the total amount from urine at 48h and eliminated almost all at 72h. The test item was removed more than 98% of the cumulative amount from bile at 24h and eliminated almost all at 48h. Feces were the main excretion pathway for the test item, followed by urine. Although the amount removed through urination and bile was account for less than 1% and 0.37% of that through feces, respectively, but the second peck concentration of test item according to the c-t curve in 6-8h indicate that existence of enterohepatic cycling. The test item was rapidly distributed to main organs, especially stomach and intestine. The test item is removed more than 50% of the total amount from organs and tissues in 24h.The test item can distribute to brain through blood brain barrier.

Applicant's summary and conclusion

Conclusions:
Interpretation of results: bioaccumulation potential cannot be judged based on study results
The study has some deviations and not all information to judge the validity is available, the information in the report is incomplete
Executive summary:

Abstract from study report:

Toxicokinetics study of α,α,α',α'-tetramethyl-m-xylene-α,α'-diol in rats was performed to assess toxicokinetic characterization by different doses, routes and ways of administration. This study contained three parts, including toxicokinetics study by acute intravenous administration, toxicokinetics study by acute oral administration and toxicokinetics study by 14-day repeated dose oral administration.The other study of acute oral administration was aim to assess toxicokinetic characterization of absorption, distribution, andexcretionin vivo.

FortySD rats were randomly divided into 5 groups (6 animal/ group). Two rats were used as control in each group. Intoxicokinetics studies,rats were treated with 1 mg/kgα,α,α',α'-tetramethyl-m-xylene-α,α'-diol by acute intravenous administration,10, 50 and 100 mg/kg test itemby acute oral administration, and50 mg/kg test itemby 14-day repeated dose oral administration, respectively. Rats were fixed in holders after the last treatment. Blood was with drawn (by direct venous puncture) from the jugular vein at 1, 5, 10, 15 and 30 min, and 1, 2, 4, 6, 8, 12, 24, 48 and 72 h after the last treatmentto obtain plasma.

Urine and fecal samples of six rats were collected bycontinuoussegment method in metabolic cages. Urine samples were stored at -80by sterile tubes. Weights of feces were measured after drying. Fecal samples were stored at -80. Bile samples of 6 rats were collected bycontinuoussegment method and stored at -80by sterile tubes. Six rats were killed by exsanguination and organs (blood, heart, brain, liver, kidney, lung, spleen, skeletal muscle, adipose tissue, reproductive organs and target organs) were collected bycontinuoussegment method and stored at -80by sterile tubes. Tworats were used as control in each group.

The plasma concentrations of test item prototype were determined by LC-MS/MS .Parameters of Cmax, AUCand elimination half-lives were compared among different groups. Results indicated that the method waspreciseand highly specific. Liner range was between10 and 2000 ng/mL.Precision of intraday and interday were between1.00% and 2.72%. Its recovery was 101.28%and mean matrixeffect factor was 96.98%. Mean stability ratio of instant test of plasma samples to subsequent test of samples stored at roomtemperature for 53 hours was 94.67%. Meanstability ratio of instant test of quality control sample to subsequent test of sample stored at 2 -8for 63 hours was 103.28%. Mean stability ratio of instant test of quality control samples to subsequent test of sample stored at roomtemperature for 17 hours was 95.81%. Mean stability ratio of instant test of quality control sample to sample (stored at -80°C) tested after 4 freeze-thaw cycles was 101.08%. The results above demonstrated that methods in this study met the requirements of “The Guidelines for the Testing of Chemicals (State Environmental Protection Administration of China, 2004.5, 417, Toxicokinetics Study)”.

Data was processed by software DAS2.0. Parameters were given below:

toxicokinetics study by acute intravenous administration: 0.31±0.34 h (Tmax) after administration, the concentration of test item is the peak value 575.75±41.28 μg/L (Cmax); the elimination half-life t1/2z is 39.73±28.89 h and the clearance CLz is 32.34±18.67 L/h/kg; the apparent volume of distribution Vz is 1335.89±741.50 L/kg, which indicates the possible cumulative effect of test item in some tissues and /or organs;

toxicokinetics study by acute oral administration(10, 50, 100mg/kg): 4.10±6.12, 0.15±0.06 and 0.20±0.04h (Tmax) after administration, the concentration of test item reach the peak value 397.57±246.16, 7804.17±4794.40 and 17538.15±9498.40 μg/L (Cmax), respectively; the elimination half-life t1/2z are 5.83±3.31, 14.00±5.40 and 8.99±4.27h, and the clearance CLz are 1.37±0.68, 3.72±0.83 and 3.10±1.09 L/h/kg, respectively; the apparent volume of distribution Vz are 13.62±11.07, 71.78±26.44 and 40.90±23.82 L/kg, which show the possible cumulative effect of test item in some tissues and /or organs; thebioavailabilityF are 48.53, 18.08 and 37.54%;

toxicokinetics study by 14-day repeated dose oral administration: Tmax is 4.11±9.74h, Cmax is 2660.00±1269.48μg/L, t1/2z is 15.38±4.06 h, CLz is 2.87±1.99 L/h/kg, Vz is 70.62±65.57 L/kg. Parameters of Tmax, Cmax, CLz and Vz in 14-day repeated dose oral administration have no significant differences with that in acute oraladministration. This effect indicated that repeated dose administration made no difference with single dose administration for the test item.

Results of acute oral administrationmetabolism studywere given below:

Feces were the main excretion pathway for the test item. The test item was removed more than 98% of the cumulative amount at 24h and eliminated almost all at 48h. The test item was removed more than 98% of the total amount from urine at 48h and eliminated almost all at 72h. The test item was removed more than 98% of the cumulative amount from bile at 24h and eliminated almost all at 48h. Feces were the main excretion pathway for the test item, followed by urine. Although the amount removed through urination and bile was account for less than 1% and 0.37% of that through feces, respectively, but the second peck concentration of test item according to the c-t curve in 6-8h indicate that existence of enterohepatic cycling. The test item was rapidly distributed to main organs, especially stomach and intestine. The test item is removed more than 50% of the total amount from organs and tissues in 24h.The test item can distribute to brain through blood brain barrier.