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Diss Factsheets

Toxicological information

Basic toxicokinetics

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Administrative data

Endpoint:
basic toxicokinetics in vivo
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
No data
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The study was well documented and meets generally accepted scientific principles, but was not conducted in compliance with GLP.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2001
Report date:
2001

Materials and methods

Objective of study:
metabolism
Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
The objectives of the study were to develop high-pressure liquid chromatography conditions to obtain profiles for the metabolites of MM in rat urine, and elucidate the structures of all the major metabolites.
GLP compliance:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
Hexamethyldisiloxane
EC Number:
203-492-7
EC Name:
Hexamethyldisiloxane
Cas Number:
107-46-0
Molecular formula:
C6H18OSi2
IUPAC Name:
Hexamethyldisiloxane
Radiolabelling:
other: 14C-MM

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
female

Administration / exposure

Route of administration:
other: oral and IV
Vehicle:
unchanged (no vehicle)
Duration and frequency of treatment / exposure:
Single dose
Doses / concentrations
Remarks:
Doses / Concentrations:
Oral: 300 mg/kg bw
IV: 80 mg/kg bw
No. of animals per sex per dose / concentration:
4 females for oral and 2 females for i.v.
Control animals:
no

Results and discussion

Main ADME results
Type:
metabolism
Results:
major metabolites identified: Me2Si(OH)2; HOMe2SiCH2OH; HOCH2Me2SiOSiMe2CH2OH (predominant); HOCH2Me2SiOSiMe3; HOMe2SiOSiMe3; Me3SiOH.

Metabolite characterisation studies

Metabolites identified:
yes
Details on metabolites:
The following are among the major metabolites identified: Me2Si(OH)2; HOMe2SiCH2OH; HOCH2Me2SiOSiMe2CH2OH (predominant); HOCH2Me2SiOSiMe3; HOMe2SiOSiMe3; Me3SiOH. Besides these there were also three other metabolites: HOMe2SiOSiMe2CH2OH; 2,2,5,5-tetramethyl-2,5-disila-1,3-dioxalene and 2,2,5,5-tetramethyl-1,4-dioxa-2,5-disilacyclohexane inferred from GC-MS analyses. Their presence in the HPLC metabolite profile was not established. No parent MM was present in urine.

Any other information on results incl. tables

The presence of certain metabolites such as Me2Si(OH)2; HOMe2SiCH2OH clearly establish some demethylation at the silicon-methyl bonds. Metabolites (abundant in hydroxymethyl groups) of this linear siloxane are structurally different from that obtained for cyclic siloxanes (D4 and D5, which are mainly silanols) except for the commonly present Me2Si(OH)2 (dimethylsilanediol).

Applicant's summary and conclusion

Conclusions:
Interpretation of results : no bioaccumulation potential based on study results
In a non-GLP study into the metabolism of hexamethyldisiloxane (reliability score 2), metabolites (abundant in hydroxymethyl groups) of this linear siloxane were found to be structurally different from that obtained for cyclic siloxanes (D4 and D5, which are mainly silanols) except for the commonly present dimethylsilanediol.
Executive summary:

In a non-GLP study into the metabolism of hexamethyldisiloxane (reliability score 2), metabolites (abundant in hydroxymethyl groups) of this linear siloxane were found to be structurally different from that obtained for cyclic siloxanes (D4 and D5, which are mainly silanols) except for the commonly present dimethylsilanediol.