1-[2-(2-chloroethoxy)phenylsulfonyl]-3-(4-methoxy-6-methyl-1,3,5-triazin-2-yl)urea;triasulfuron (ISO)

Dermal absorption

Administrative data

Endpoint:

dermal absorption in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

24 Oct 2011 to 01 Nov 2011

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2012

Report date:

2012

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 428 (Skin Absorption: In Vitro Method)

Version / remarks:

2004

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

2-(2-chloroethoxy)-N-[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)carbamoyl]benzene-1-sulfonamide

EC Number:

617-298-9

Cas Number:

82097-50-5

Molecular formula:

C14H16ClN5O5S

IUPAC Name:

2-(2-chloroethoxy)-N-[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)carbamoyl]benzene-1-sulfonamide

Radiolabelling:

yes

Administration / exposure

Type of coverage:

open

Vehicle:

water

Duration of exposure:

24 hours

Doses:

- 33.3 % w/w aqueous slurry, nominally containing 66.7 g/kg
- 1/444 w/w dilutions, nominally containing 0.15 g/kg
- 1/888 w/w dilutions, nominally containing 0.075 g/kg

Results and discussion

Percutaneous absorption

Percutaneous absorption 1

Time point:

24 h

Concentrate / Dilution:

concentrate

Dose:

33 % (w/w) , corresponding to 67.3 g substance/kg

Parameter:

percentage

Absorption:

0.04 %

Remarks on result:

other: dermal absorption = (stratum corneum (tape strips 3-5) + remaining epidermis + receptor fluid) + k * SD

Percutaneous absorption 2

Time point:

24 h

Concentrate / Dilution:

dilution

Dose:

1/444 (w/w), corresponding to 0.168 g substance/kg

Parameter:

percentage

Absorption:

1.8 %

Remarks on result:

other: dermal absorption = (stratum corneum (tape strips 3-5) + remaining epidermis + receptor fluid) + k * SD

Percutaneous absorption 3

Time point:

24 h

Concentrate / Dilution:

dilution

Dose:

1/888 (w/w), corresponding to 0.086 g substance/kg

Parameter:

percentage

Absorption:

4.4 %

Remarks on result:

other: dermal absorption = (stratum corneum (tape strips 3-5) + remaining epidermis + receptor fluid) + k * SD

Any other information on results incl. tables

STABILITY IN THE FORMULATIONS

(14C)-labelled test substance, when formulated as a 66.7 g/kg, 0.15 g/kg and 0.075 g/kg formulation, was shown to be stable by HPLC for a period of 1 day, which is a period of time longer than that used in the study.

Radiochemical purities of greater than 97 % were seen in all dose preparations both prior to application and one day post dose preparation.

 

PARTICLE SIZE

Particle size analysis of the dose preparations confirmed that the mean particle sizes were 6.95 μm (2.5 – 17.5 μm range), 7.43 μm (2.5 – 20 μm range) and 7.26 μm (2.5 – 21.25 μm range) for the 33.3 % w/w aqueous slurry and the 1/444 w/w and 1/888 w/w aqueous dilutions, respectively.

 

Table 1. Individual Distribution of the test substance from the 33.3 % w/w Aqueous Slurry of the Formulation Concentrate in the Test System

Test Compartment	Percentage of Dose Recovered (%)
	Cell 31	Cell 33	Cell 35	Cell 36	Cell 38	Cell 39
Donor chamber	0.004	0.002	0	0.011	0.02	0.02
Skin wash	108	99.9	114	110	113	109
Stratum corneum (Tape strips 1 & 2)	0.008	0.018	0.013	0.009	0.017	0.008
Stratum corneum (Tape strips 3 - 5)	0.004	0.007	0.005	0.006	0.01	NS
Remaining epidermis	0.007	0.02	0.009	0.01	0.007	0.044
Receptor fluid	0.012	0	0.007	0.001	0.004	0.002
Total recovered	108	100	114	110	113	109
Dermal absorption per cell	0.023	0.027		0.017		0.046

Stratum corneum = amount in tape strips; Remaining epidermis = epidermal tissue remaining after tape stripping

* (Cell 35 and 38 were excluded in the calculation of the mean absorption due to high recovery).

 

Table 2. Individual Distribution of the test substance from the 1/444 w/w Aqueous Slurry of the Formulation Concentrate in the Test System

Test Compartment	Percentage of Dose Recovered (%)
	Cell 1	Cell 2	Cell 3	Cell 6	Cell 7	Cell 15
Donor chamber	0	2.62	0	0.238	0	0
Skin wash	97.5	101	100	103	99.4	105
Stratum corneum (Tape strips 1 & 2)	0.183	0.231	0.423	0.287	0.315	0.064*
Stratum corneum (Tape strips 3 - 5)	0.183	0.358	0.367	0.127	0.166	0.025*
Remaining epidermis	1.57	1.44	0.973	0.804	0.553	0.284
Receptor fluid	1.35	0.149	0.075	0.139	0.094	0.056
Total recovered	101	106	102	104	100	105
Dermal absorption per cell	3.103	1.947	1.415	1.070	0.813	0.340

Stratum corneum = amount in tape strips; Remaining epidermis = epidermal tissue remaining after tape stripping

 

Table 3. Individual Distribution of the test substance from the 1/888 w/w Aqueous Slurry of the Formulation Concentrate in the Test System

Test Compartment	Percentage of Dose Recovered (%)
	Cell 5	Cell 9	Cell 10	Cell 19	Cell 26	Cell 28
Donor chamber	0.000*	0.817	0	0	0	0
Skin wash	106	102	93.9	93.4	103	99.9
Stratum corneum (Tape strips 1 & 2)	0.487	NS	0.989	0.534	0.172	0.381
Stratum corneum (Tape strips 3 - 5)	0.841	NS	0.985	0.414	0.210	0.457
Remaining epidermis	2.10	3.00	4.22	2.74	0.724	1.28
Receptor fluid	0.086	0.194	0.078	0.141	0.143	0.224
Total recovered	110	106	100	97.2	104	102
Dermal absorption per cell	3.027	3.194	5.283	3.295	1.077	1.961

Stratum corneum = amount in tape strips; Remaining epidermis = epidermal tissue remaining after tape stripping

Applicant's summary and conclusion

Conclusions:

The penetration of the test substance from a 33.3 % w/w (corresponding to 67.3 g substance/kg) slurry, 1/444 w/w (corresponding to 0.168 g substance/kg) and 1/888 w/w (corresponding to 0.086 substance/kg) aqueous spray strength dilutions of the concentrate slurry, through human epidermis is very slow and the vast majority of the applied dose could be removed by gentle skin washing after 24 hours. The overall absorption of the test substance over 24 hours was 0.04, 1.8, and 4.4 %, for the 33.3 % w/w slurry, 1/444 w/w dilution, and 1/888 w/w dilution, respectively. These data predict that the systemic exposure to the test substance following dermal contact with this formulation would be minimal.

Executive summary:

The dermal absorption and distribution of the test substance from formulation concentrate was measured in human skin in a study conducted according to OECD TG 428 following GLP. Doses of (14C)-test substance were applied as a 33.3 % w/w aqueous slurry of the formulation concentrate (nominally, 66.7 g/kg) and as 1/444 w/w (nominally, 0.15 g/kg) and 1/888 w/w (nominally, 0.075 g/kg) aqueous spray strength aqueous dilutions of the slurry. The doses were applied at 10 μL/cm2 and left unoccluded for an exposure period of 24 hours. The absorption process was followed by taking samples of the receptor fluid (50 % v/v ethanol/water) at recorded intervals throughout the exposure period. The distribution of the test substance within the test system and a 24 hour absorption profile were determined, using liquid scintillation counting (LSC). The absorbed (systemically available) dose is calculated based on EFSA guidance on dermal absorption (2017). Based on the fact that the study has a duration of 24 hours, < 75 % of the permeation occurs in the first half of the study, and that the tape strips were analysed individually, the tape stips 1 + 2 were excluded from the absorption calculation. Dermal absorption = % in receptor fluid + % in skin sample. 

For the 33.3 % w/w aqueous slurry of the formulation concentrate slurry, the mean total recovery was 109 % of the dose applied. The overall dermal absorption of the test substance from the 33.3 % w/w aqueous slurry of the formulation concentrate through human epidermis was 0.04 % during the 24 hour exposure period. The amount absorbed at 24 hours was 0.028 μg/cm² (0.004 % of the dose applied). The amounts absorbed at 6, 8 and 12 hours were 0.021 μg/cm² (0.003 %), 0.021 μg/cm² (0.003 %) and 0.030 μg/cm² (0.004 %), respectively. These values were below the limit of quantitation (0.039 μg/cm², 0.006 %). The vast majority of the applied test substance (mean 109 %) was washed off the skin at 24 hours. 

For the 1/444 w/w aqueous dilution of the formulation concentrate slurry, the mean total recovery was 104 % of the dose applied. The overall dermal absorption of the test substance from the 1/444 w/w aqueous dilution of the formulation concentrate slurry through human epidermis was 1.8 % during the 24 hour exposure period. The amount absorbed at 24 hours was 0.0017 μg/cm² (0.103 % of the dose applied). The amounts absorbed at 6, 8 and 12 hours were 0.0005 μg/cm² (0.032 %), 0.0007 μg/cm² (0.040 %) and 0.0008 μg/cm² (0.050 %), respectively. The values for 6 and 8 hours were below the limit of quantitation (0.0008 μg/cm², 0.047 %).The vast majority of the applied test substance (mean 102 %) was washed off the skin at 24 hours. 

For the 1/888 w/w aqueous dilution of the formulation concentrate slurry, the mean total recovery was 103 % of the dose applied. The overall dermal absorption of the test substance from the 1/888 w/w aqueous dilution of the formulation concentrate slurry through human epidermis was 4.4 % during the 24 hour exposure period. The amount absorbed at 24 hours was 0.0012 μg/cm² (0.143 % of the dose applied). The amounts absorbed at 6, 8 and 12 hours were 0.0007 μg/cm² (0.080 %), 0.0007 μg/cm² (0.086 %) and 0.0009 μg/cm² (0.102 %), respectively. The values for 6 and 8 hours were below the limit of quantitation (0.0008 μg/cm², 0.090 %).The vast majority of the applied test substance (mean 99.8 %) was washed off the skin at 24 hours. 

The penetration of the test substance from a 33.3 % w/w slurry, 1/444 w/w and 1/888 w/w aqueous spray strength dilutions of the concentrate slurry, through human epidermis is very slow and the vast majority of the applied dose could be removed by gentle skin washing after 24 hours. The overall absorption of the test substance over 24 hours was 0.04, 1.8, and 4.4 %, for the 33.3 % w/w slurry, 1/444 w/w dilution, and 1/888 w/w dilution, respectively. These data predict that the systemic exposure to the test substance following dermal contact with this formulation would be minimal.