2,2-bis(methylthio)propane

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

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:

study report

Title:

Unnamed

Year:

2014

Report date:

2014

Materials and methods

Objective of study:

absorption

excretion

Principles of method if other than guideline:

The objective of this study was to characterise the routes and rates of excretion of BMTP and/or its radiolabelled metabolites in urine, faeces and expired air.

GLP compliance:

no

Remarks:

This is a non-regulatory study for which a claim of GLP compliance has not be made. However, the laboratory procedures were fully commensurate with International Standards of GLP.

Test material

Test material information

Constituent 1

Reference substance name:

-

EC Number:

478-900-1

EC Name:

-

Cas Number:

6156-18-9

Molecular formula:

C5 H12 S2

IUPAC Name:

2,2-bis(methylthio)propane

Test material form:

liquid

Test animals

Species:

rat

Strain:

other: Han Wistar

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River, UK
- Age at study initiation: no data
- Weight at study initiation: 208 and 238 g
- Housing:3 per cage prior to dosing
- Diet (ad libitum): SQC Rat and Mouse Maintenance Diet No 1, Expanded (Special Diets Services)
- Water (ad libitum): mains water
- Acclimation period: 7 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 to 24
- Humidity (%): 42 and 65
- Air changes (per hr): 15 to 20
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
The test substance was supplied pre-formulated, ready to administer to the animals.

Duration and frequency of treatment / exposure:

Single administration

Doses / concentrations

Dose / conc.:

160 mg/kg bw/day (nominal)

Remarks:

Nominal radioactive dose: 5 MBq/kg

No. of animals per sex per dose / concentration:

3

Control animals:

no

Details on study design:

- Dose selection rationale: from subacute repeated dose toxicological studies by oral route, a NOAEL was established at 160 mg/kg bw/day.

Details on dosing and sampling:

- Excretion Balance Investigation
Following dose administration, rats were placed in all-glass metabolism cages suitable for the separate collection of urine and faeces.
Urine and faeces were collected over the following time intervals after dose administration:
• 0-6, 6-24, 24-48, 48-72, 72-96, 96-120, 120-144 and 144-168 hours.
Urine collection vessels were rinsed with a small volume of water (2 to 5 mL) which was added to the urine sample.
At each collection, cage debris was removed and the cages were rinsed with a small volume of water. The aqueous cage washings were retained separately for each animal and time point. Cage debris was pooled for each animal over the entire collection period. Following the final water wash, methanol was used to rinse the cages.
In order that any radioactivity excreted in expired air may be collected, air (dried over drierite or calcium chloride and carbon dioxide removed with soda lime) was drawn through the cage by vacuum. Air exiting the cage was passed through two CO2 traps in series, each containing a solution of 2-ethoxyethanol : ethanolamine (3:1 v/v), duplicate carbon traps and a cold trap, to collect any potential volatile materials. The cold trap contained ethanol, cooled over wet-ice, which was replaced at the end of each working day.
Expired air trapping solutions and carbon traps were collected at the following time intervals after dose administration:
• 0-6, 6-24, 24-48 and 48-72 hours.
Radioactivity levels in expired air traps were so low (<0.5% of the administered radioactivity in the 48-72 hours collection period) that traps were discontinued after this time.
Following the final excreta collection, a sample of blood was taken by cardiac puncture (whilst under terminal anaesthesia), after which the animals were killed by cervical dislocation and exsanguination following isoflurane anaesthesia. Carcasses were retained for analysis.
Radioactivity was determined in urine, faeces, cage debris, cage washings (aqueous and organic), expired air traps, whole blood and carcasses, using the methods presented in the Sample Preparation section.

- Sample Preparation
Volumes and/or weights of biological samples were measured, where appropriate.
. Urine, cage washings, liquid expired air trap contents
Weighed aliquots were added to liquid scintillant for analysis by LSC.
. Faeces and cage debris
Faeces and cage debris were homogenised in deionised water. Aliquots of the homogenates (ca 0.1g, weighed) were taken and solubilised using Soluene 350 (Perkin Elmer LAS (UK) Ltd), with subsequent addition of liquid scintillant and analysis by LSC.
. Blood
Aliquots (ca 0.1g, weighed) were solubilised using Solvable (Perkin Elmer LAS (UK) Ltd), with subsequent addition of liquid scintillant and analysis by LSC.
. Carbon traps
Carbon trap contents were combusted in an oxygen atmosphere and the resultant gasses trapped using Carbosorb® and Permafluor®, followed by analysis by LSC.
. Carcasses
Carcasses were digested in a solution of potassium hydroxide in methanol (approximately 40%, w/v). Liquid scintillant was added to the samples prior to analysis by LSC.

- Liquid Scintillation Counting
A suitable scintillation counter was used. Radioassays were performed on duplicate weighed aliquots (all samples).
Efficiency correlation curves were prepared and routinely checked by the use of sealed [14C]-toluene and Ultima Gold™ quenched standards (Perkin Elmer LAS (UK) Ltd).
The limit of quantification for each batch of samples analysed was taken as twice the mean background disintegration rate obtained from vials containing an equivalent volume of an appropriate solvent in liquid scintillant

Results and discussion

Main ADME results

Main ADME results 1

Type:

other: Overall recovery

Results:

97.0%

Main ADME results 2

Type:

other: Excretion in urine

Results:

73.3%

Main ADME results 3

Type:

other: Cage washes

Results:

15.8%

Main ADME results 4

Type:

other: Ecretion in faeces

Results:

1.3%

Main ADME results 5

Type:

other: Excretion in expired air

Results:

< 5%

Any other information on results incl. tables

Animal Observations

During the course of the study, no overt pharmacological or toxicological signs that could have been attributed to the administration ofBMTPwere observed in the test animals.

Excretion Balance

All values quoted in this section are means for the two animals used for this study.

Overall recovery of radioactivity was 97.0% over the 168 hour collection period, with excretion principally in the urine (73.3%) and cage washes (15.8%, probably mostly derived for urine). Only low levels of radioactivity were present in faeces (1.3%) and cage debris (0.1%). Radioactivity was collected in the expired air traps (principally in the ethoxyethanol : ethanolamine traps) but this accounted for less than 5% of the administered dose.

Radioactivity remained detectable in both blood (0.984 µg equiv/g) and the carcass (2.68 µg equiv/g; 1.7% of the administered dose) at 168 hours post-dose.

Applicant's summary and conclusion

Conclusions:

Nearly 100% of the dose was absorbed, the principal route of excretion was in the urine, with only low levels recovered in either faeces or expired air.

Executive summary:

The excretion of radioactivity has been investigated following oral administration of [14C]-BMTP to male rats. Two male rats of the Han Wistar strain received a single oral administration of [14C]-BMTP, by gavage at a nominal dose level of 160 mg/kg. Urine and faeces collected at sampling periods up to 168 hours. Expired air was drawn through a series of traps, designed to collect volatile components, at times up to 72 hours. Following each urine/faecal collection, cages were washed with a small volume of water and any cage debris removed. Blood was collected at 168 hours post-dose, prior to the animals being humanely killed and carcasses retained. Radioactivity in blood, excreta and carcasses was determined by liquid scintillation counting. The mean recovery of radioactivity was 97.0% over the collection period. The majority of the radioactivity recovered was in the urine (73.3%) and cage washes (15.8%), with limited levels in faeces (1.3%) and cage debris (0.1%). Expired air traps contained radioactivity but this accounted for less than 5% of the administered dose. Low levels of radioactivity were retained in both blood (0.984 µg equiv/g) and the carcass (2.68 µg equiv/g; 1.7% of the dose). In conclusion, nearly 100% of the dose was absorbed, the principal route of excretion was in the urine, with only low levels recovered in either faeces or expired air.