dinotefuran (ISO); 1-methyl-2-nitro-3-(tetrahydro-3-furylmethyl)guanidine

Dermal absorption

Administrative data

Endpoint:

dermal absorption in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

20/09/2005 - 05/04/2006

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP, Guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2006

Report date:

2006

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.7600 (Dermal Penetration)

Version / remarks:

(1998)

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

(RS)-1-methyl-2-nitro-3-(tetrahydro-3-furylmethyl)guanidine

EC Number:

605-399-0

Cas Number:

165252-70-0

Molecular formula:

C7H14N4O3

IUPAC Name:

(RS)-1-methyl-2-nitro-3-(tetrahydro-3-furylmethyl)guanidine

Test material form:

other: soild

Details on test material:

Purity non-labelled test item: 97.26%
Purity labelled test item: Radiochemical purity after purification 98.5% by HPLC
Batch No. non-labelled test item: 5500310
Batch No. labelled test item: CP-2499

Radiolabelling:

yes

Remarks:

[14C- guanidine]dinotefuran ([G-14C])

Test animals

Species:

rat

Strain:

other: Sprague Dawley, SPF quality (outbred)

Sex:

male

Details on test animals or test system and environmental conditions:

Source: RCC Ltd, Laboratory Animal Services, Füllinsdorf, Switzerland
Age: 8 – 9weeks at acclimatization
Body weight: approximately 260 g

Administration / exposure

Type of coverage:

open

Vehicle:

water

Remarks:

MilliQ

Duration of exposure:

Exposre period: 24 hours, with interim kills of 4 rats per group after 0.5, 1, 2, 4 and 10 hours exposure.

Doses:

Concentration of test substance: 3.2, 30 and 302 µg/cm2
Specific gravity: 156 µCi/mg (5760 kBq/mg)

No. of animals per group:

24 males/6 subgroups/group

Control animals:

no

Details on study design:

Preparation of test site: Clipped and wiped with acetone under anaesthesia with isofluorane. O-ring (inside area of approximately 25 - 35 cm2) was used.
Volume applied: 100µL of application solution was applied to the skin inside the O-ring using a syringe and spread evenly.
Size of test site: 10 cm²
Sampling time: 0.5, 1, 2, 4, 10 and 24 hours after initiation of skin contact

Housing and feeding condition: animals were housed individually throughout the experiment and fed certified standard diet ad libitum.

Details on in vitro test system (if applicable):

Not applicable

Results and discussion

Signs and symptoms of toxicity:

no effects

Remarks:

The slight weight loss of animals was attributed to the stress and discomfort during the experiment. At dissection urinary calculi were found in the urinary bladder with cloudy urine of one animal of group 3.

Dermal irritation:

no effects

Remarks:

There was no evidence of skin irritation.

Absorption in different matrices:

Percutaneous absorption:

Low dose group (see Table 2):
After dermal application, systemic absorption was increased with the exposure time from 0.5 hours to 10 hours, but thereafter it remained almost constant. Therefore systemic absorption during a 24-hour exposure was calculated to be 0.81% of the applied dose. The concentration of radioactivity (RA) in blood was below the limit of quantification (LOQ) at all sampling time points. A major part of the applied RA was found in the skin wash which decreased with exposure time from 85% of dose after 0.5 hours to 60% of dose after 10 hours but no further change was observed between 10 hours and 24 hours. Correspondingly, the RA in the stratum corneum (tape strips) increased from 7.4% after 0.5 hours to 35% of the applied dose after 10 hours of exposure. The lower skin layers, corium and subcutis, showed very low amounts of RA (less than 1%) and 0.3-4.8% of the dose was recovered in the cover and O-ring. The systemically absorbed test item was rapidly excreted with the urine and only 0.11 % of the dose remained in the animals 24 hours after the start of exposure. The mean penetration rate for the 24-hour exposure time was calculated to be 0.0011 µg/cm2/hour.

Middle dose group (See Table 3):
After dermal application, absorption was only 0.48% during an exposure of 24 hours. The highest values were found 1 and 4 hours after start of exposure accounting for 1.43% and 1.15% of the applied dose, respectively, but a high inter-individual variation was observed. The concentrations of RA in blood were below the limit of quantification (LOQ) at most of the sampling time points, and 0.0033 and 0.0134 ppm dinotefuran equivalents were determined after 0.5 and 1 hour, respectively. A major part of the applied RA was recovered in the skin wash which was decreased with exposure time from 90% of dose after 0.5 hours to 69% of dose after 10 hours but no further change was observed between 10 hours and 24 hours. Correspondingly, the RA in the stratum corneum increased with exposure time and reached 26% of the applied dose after an exposure period of 24 hours. The lower skin layers, corium and subcutis, showed very low amounts of RA (less than 0.5%) and in the range 0.05-3.2% of the dose were recovered in the cover and O-ring. The systemically absorbed test item was rapidly excreted with the urine and only 0.09 % of the dose remained in the animals 24 hours after the start of exposure. The mean penetration rate for the 24 hours exposure time was calculated to be 0.0060 µg/cm2/hour.

High dose group (see Table 4):
After dermal application, absorption was 1.04% during an exposure of 24 hours. Higher values of dermal absorption were found at 1, 4 and 10 hours after start of exposure accounting for 1.41%, 2.10% and 1.44% of the applied dose, respectively, but a high inter-individual variation was observed. The highest concentration in blood was found 1 hour after the start of exposure accounting for 0.1773 ppm dinotefuran equivalents. Thereafter the concentrations decreased rapidly to values close to the limit of quantification. A large amount of RA was found in the skin wash. It decreased only slightly with ongoing exposure time, i.e. 93% of the dose after 0.5 hours to 86% of the dose after 10 hours. After 1 hour of exposure 8% of the applied dose had penetrated into the stratum corneum. This level was almost constant until 24 hours. The lower skin layers, corium and subcutis, showed very low amounts of RA. The systemically absorbed test item was rapidly excreted with the urine and only 0.09 % of the dose was still remaining in the animals 24 hours after start of exposure. The mean penetration rate for the 24 hours exposure time was calculated to be 0.1309 µg/cm2/hour.

Analysis of skin wash:
See Table 5
The skin wash samples of the individual animals were pooled for every sampling time point and dose level, and analyzed by HPLC. In all analyses more than 96% of the RA was found as unchanged dinotefuran. Therefore it was concluded that the applied test substance remained stable at the application site over the whole exposure period.

Total recovery:

See Table 1
Mean total recoveries of radioactivity were high (95.4-99.1%) in all dose groups at all time points and the systemically absorbed dose was rapidly excreted, predominantly in urine.

Percutaneous absorption

Percutaneous absorption 1

Dose:

3.2 µg/cm²

Parameter:

percentage

Absorption:

97.2 %

Remarks on result:

other: 0.5 h

Percutaneous absorption 2

Dose:

3.2 µg/cm²

Parameter:

percentage

Absorption:

99.1 %

Remarks on result:

other: 4 h

Percutaneous absorption 3

Dose:

3.2 µg/cm²

Parameter:

percentage

Absorption:

96.9 %

Remarks on result:

other: 24 h

Percutaneous absorption 4

Dose:

30 µg/cm²

Parameter:

percentage

Absorption:

96.6 %

Remarks on result:

other: 0.5 h

Percutaneous absorption 5

Dose:

30 µg/cm²

Parameter:

percentage

Absorption:

97.7 %

Remarks on result:

other: 4 h

Percutaneous absorption 6

Dose:

30 µg/cm²

Parameter:

percentage

Absorption:

97.7 %

Remarks on result:

other: 24 h

Percutaneous absorption 7

Dose:

302 µg/cm²

Parameter:

percentage

Absorption:

97 %

Remarks on result:

other: 0.5 h

Percutaneous absorption 8

Dose:

302 µg/cm²

Parameter:

percentage

Absorption:

95.4 %

Remarks on result:

other: 4 h

Percutaneous absorption 9

Dose:

302 µg/cm²

Parameter:

percentage

Absorption:

96.3 %

Remarks on result:

other: 24 h

Any other information on results incl. tables

Table 1: Summary of mean mass balance and systemic absorption

Dose level (µg/cm^2)	Matrix	Radioactivity in%of applied dose:
		0-0.5 h	0-1 h	0-2 h	0-4 h	0-10 h	0-24 h
3.2	Systemic absorption	0.2	0.2	0.4	0.7	1.2	0.8
	Dislodged dose	89.5	78.7	67.4	68.9	61.5	60.7
	Stratum corneum (outer skin)	7.4	18.1	31.0	29.2	34.8	34.6
	Corium+subcutis (inner skin)	0.1	0.2	0.3	0.5	0.6	0.8
	Total	97.2	97.2	99.1	99.1	97.9	96.9
30	Systemic absorption	0.3	1.4	0.3	1.2	0.8	0.5
	Dislodged dose	90.5	83.8	74.5	77.6	71.9	71.2
	Stratum corneum (outer skin)	5.6	12.5	21.9	18.8	24.7	25.6
	Corium+subcutis (inner skin)	0.2	0.5	0.2	0.1	0.2	0.4
	Total	96.6	98.3	96.9	97.7	97.6	97.7
302	Systemic absorption	0.2	1.4	0.9	2.1	1.4	1.0
	Dislodged dose	93.3	85.8	88.9	86.7	86.1	86.1
	Stratum corneum (outer skin)	3.4	8.0	7.8	6.4	7.8	9.0
	Corium+subcutis (inner skin)	0.1	0.5	0.1	0.2	0.1	0.2
	Total	97.0	95.7	97.7	95.4	95.4	96.3

 

Table 2:Balance of radioactivity and excretion pattern – low dose group (3.2µg/cm²)

Matrix	Radioactivity in%of applied dose:
	0-0.5 hours		0-1 hours		0-2 hours		0-4 hours		0-10 hours		0-24 hours
	Mean	SD	Mean	SD	Mean	SD	Mean	SD	Mean	SD	Mean	SD
Urine	<0.01	<0.01	0.02	0.01	0.14	0.16	0.45	0.49	0.97	0.50	0.62	0.48
Faeces	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	0.02	<0.01
Cage wash	<0.01	<0.01	<0.01	<0.01	<0.01	0.01	0.03	0.01	0.02	0.01	0.05	0.07
TOTAL EXCRETION	0.01	<0.01	0.03	0.02	0.16	0.18	0.48	0.49	1.00	0.51	0.69	0.53
Blood	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01
Untreated skin	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01
GI tract + contents	0.02	<0.01	0.02	<0.01	0.03	<0.01	0.03	0.01	0.03	<0.01	0.02	<0.01
Carcass	0.13	0.01	0.15	0.02	0.16	0.03	0.14	0.05	0.12	0.02	0.09	0.02
Sub-total	0.16	0.02	0.18	0.03	0.19	0.04	0.18	0.06	0.15	0.02	0.11	0.02
SYSTEMICABSORPTION	0.17	0.02	0.20	0.03	0.35	0.21	0.65	0.55	1.15	0.52	0.81	0.52
TapeStrips (stratum corneum)	7.42	0.31	18.06	6.04	30.97	4.40	29.15	2.88	34.77	5.40	34.63	1.08
Remaining treated skin	0.09	0.03	0.17	0.03	0.31	0.10	0.45	0.37	0.56	0.25	0.77	0.47
APPRICATION SITE	7.51	0.33	18.24	6.07	31.27	4.37	29.60	3.20	35.33	5.28	35.40	1.55
Skin wash	84.70	6.55	78.04	3.04	66.83	3.72	68.60	4.11	59.78	6.09	59.10	5.46
O-ring/covers	4.79	6.08	0.67	1.07	0.60	0.76	0.30	0.30	1.68	3.04	1.62	2.70
DISLODGEDDOSE	89.49	0.68	78.71	2.70	67.43	3.40	68.90	3.98	61.46	5.43	60.72	2.99
TOTALRECOVERY	97.18	0.56	97.15	3.38	99.05	0.98	99.14	0.80	97.93	0.58	96.93	1.63

 

Table 3:Balance of radioactivity and excretion pattern – middle dose group(30 µg/cm²)

Matrix	Radioactivity in%of applied dose:
	0-0.5 hours		0-1 hours		0-2 hours		0-4 hours		0-10 hours		0-24 hours
	Mean	SD	Mean	SD	Mean	SD	Mean	SD	Mean	SD	Mean	SD
Urine	0.04	0.04	0.40	0.42	0.12	0.02	0.88	0.88	0.65	0.66	0.36	0.26
Faeces	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	0.01	<0.01
Cage wash	<0.01	<0.01	0.03	0.05	<0.01	<0.01	0.05	0.05	<0.01	<0.01	<0.01	<0.01
TOTAL EXCRETION	0.04	0.04	0.43	0.46	0.13	0.02	0.93	0.93	0.67	0.67	0.38	0.27
Whole blood	<0.01	<0.01	0.03	0.02	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01
Untreated skin	<0.01	<0.01	0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01
GI tract + contents	0.02	0.01	0.09	0.09	0.02	<0.01	0.03	0.02	0.02	<0.01	0.01	<0.01
Carcass	0.20	0.10	0.87	0.57	0.14	0.01	0.17	0.04	0.10	<0.01	0.08	<0.01
Sub-total	0.24	0.12	1.00	0.67	0.17	0.02	0.21	0.06	0.12	0.01	0.09	<0.01
SYSTEMICABSORPTION	0.28	0.16	1.43	1.13	0.30	0.03	1.15	0.98	0.78	0.68	0.48	0.27
TapeStrips (stratum corneum)	5.59	1.62	12.51	4.33	21.87	1.35	18.75	3.43	24.73	5.40	25.62	3.34
Remaining treated skin	0.15	0.12	0.49	0.44	0.20	0.07	0.14	0.03	0.16	0.05	0.40	0.22
APPRICATION SITE	5.74	1.70	13.00	4.63	22.06	1.39	18.89	3.43	24.89	5.35	26.02	3.31
Skin wash	90.49	3.23	83.62	5.58	71.30	1.75	74.44	4.48	69.12	3.75	70.07	4.67
O-ring/covers	0.05	0.02	0.22	0.27	3.22	2.70	3.17	6.11	2.82	2.81	1.12	1.95
DISLODGEDDOSE	90.54	3.23	83.84	5.69	74.51	1.02	77.61	2.90	71.94	5.58	71.19	3.72
TOTALRECOVERY	96.55	3.37	98.27	0.96	96.88	0.83	97.65	1.34	97.62	1.22	97.69	1.04

 

Applicant's summary and conclusion

Conclusions:

A large proportion of the dermally applied dinotefuran (60.7 – 93.3%) remained on the surface of the skin and could be dislodged by washing, and was not available for absorption into the skin or systemic circulation. Therefore, systemic absorption of dinotefuran was very low at all time points for all dose levels.