Diquat dibromide

Dermal absorption

Administrative data

Endpoint:

dermal absorption in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1991

Report date:

1991

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

The absorption of the test material through human abdominal epidermis was measured from technical test material (17.13% w/v test substance ion) and a spray strength solution (0.45% w/v test substance ion), using glass diffusion cells in which the epidermal sheet forms a horizontal membrane sperating "donor" and "receptor" chambers.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Diquat dibromide

EC Number:

201-579-4

EC Name:

Diquat dibromide

Cas Number:

85-00-7

Molecular formula:

C12H12N2.2Br

IUPAC Name:

1,1'-ethylene 2,2'-bipyridyldiylium dibromide

Constituent 2

Reference substance name:

Water

EC Number:

231-791-2

EC Name:

Water

Cas Number:

7732-18-5

Molecular formula:

H2O

IUPAC Name:

water

Test material form:

liquid

Radiolabelling:

yes

Administration / exposure

Doses:

- Technical test material: 17.13% w/w test substance ion
- Spray strength solution: 0.45% w/v test substance ion

Details on study design:

ANALYTICAL TECHNIQUE
- Radiochemical assay: Liquid scintillation spectrometer
- Sample size: 25 µL added to scintillation fluid in vials followed by mixing
- Counting period: 10 minutes, or until 10^6 counts had been registered

Details on in vitro test system (if applicable):

In vitro model using Human abdominal whole skin (dermis plus epidermis).

Results and discussion

Absorption in different matrices:

The mean rate of absorption of the test substance from the concentrate, through abdominal skin was 8.62 µg/cm2/hr (SEM ± 1.76; n = 12). From the spray strength solution the rate was 0.24 µg/cm2/hr (SEM ± 0.06; n = 12).
A lag phase of 10-15 hours, ie a period of increasing rate of absorption before the steady state, was detected after the concentrate contacted the skin in these experiments. When the spray strength solution contacted the skin, a lag phase of between 8-12 hours was apparent. A more precise definition of the lag phase from both formulations was not possible due to the small amounts of test substance being absorbed.

Percutaneous absorption

Percutaneous absorption 1

Key result

Dose:

Concentrate (17.13 % w/w test substance ion)

Parameter:

rate

Absorption:

8.62 other: µg/cm2/hr (SEM ± 1.76; n=12)

Percutaneous absorption 2

Key result

Dose:

Spray strenght solution (0.45 % w/v test substance ion)

Parameter:

rate

Absorption:

0.24 other: µg/cm2/hr (SEM ± 0.06; n=12)

Applicant's summary and conclusion

Conclusions:

The mean steady rate of absorption of the test substance from the concentrate, through abdominal skin was 8.62 µg/cm2/hr (SEM ± 1.76; n = 12). From the spray strength solution the rate was 0.24 µg/cm2/hr (SEM ± 0.06; n = 12).

Executive summary:

The absorption of the test substance through human abdominal epidermis was measured from technical test substance material (17.13 % w/w test substance ion) and a spray strength solution (0.45 % w/ v test substance ion). Glass diffusion cells in which the epidermal sheet forms a horizontal membrane separating "donor” (outer) and "receptor" chambers were used for measuring skin absorption rates. 1.8 cm2 of epidermal surface was available for absorption and all experiments were done at 30 °C. Receptor solutions were stirred. The test substance material or the aqueous spray strength solution (1 mL), both containing [14C]test substance, was place in the donor chamber. At defined intervals (1 hour for the concentrate and 2 hours for the dilution) 25 µL samples were removed from the receptor chamber and put in scintillation fluid. The mean steady rate of absorption of the test substance from the concentrate, through abdominal skin was 8.62 µg/cm2/hr (SEM ± 1.76; n = 12). From the spray strength solution the rate was 0.24 µg/cm2/hr (SEM ± 0.06; n = 12).