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Toxicological information

Basic toxicokinetics

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Administrative data

Endpoint:
basic toxicokinetics
Type of information:
experimental study
Adequacy of study:
key study
Study period:
19/01/1998 - 27/01/2000
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP, Guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2000
Report date:
2000

Materials and methods

Objective of study:
other: to assess the extent of absorption, distribution, elimination and biotransformation of [14C] dinotefuran given to rats by 2 routs of administration
Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
EPA OPP 85-1 (Metabolism and Pharmacokinetics)
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: JMAFF 59 NohSan no. 4200
Deviations:
no
GLP compliance:
yes

Test material

Constituent 1
Chemical structure
Reference substance name:
1-methyl-2-nitro-3-(tetrahydrofuran-3-ylmethyl)guanidine
EC Number:
605-399-0
Cas Number:
165252-70-0
Molecular formula:
C7H14N4O3
IUPAC Name:
1-methyl-2-nitro-3-(tetrahydrofuran-3-ylmethyl)guanidine
Test material form:
solid: particulate/powder
Remarks:
migrated information: powder
Details on test material:
TEST MATERIAL:
1. Unlabelled dinotefuran
2. [14C-tetrahydrofuran] dinotefuran ([F-14C])
3. [14C-guanidine] dinotefuran ([G-14C])

PURITY:
1. 98.92 % (Batch no. 22-00210) and 99.47% (Batch no. OFU-1265)
2. >98% and 100%
3. >99% and 100%
Specific activity: 28.9 and 27.5 µCi/mg ([F-14C]), 42.9 and 39.2 µCi/mg ([G-14C])

BATCH NO.:
1. 22-00210 and OFU-1265
2. 5091-20 and 5109-34
3. 5091-30 and 5109-28


Radiolabelling:
yes

Test animals

Species:
rat
Strain:
other: Crl:CD(SD) BR (male), Hla(SD)CVF (male and female bile duct-cannulated rats)
Sex:
male/female
Details on test animals or test system and environmental conditions:
Source: Charles River Laboratories Inc, USA except for bile duct-cannulated rats were supplied by Hilltop Lab Animals Inc.
Age/weight at study initiation: >4 weeks old, weighing 76 - 282g or 228 - 329g (time-mated female rats) at arrival

Administration / exposure

Route of administration:
other: Administered orally by gavage or intravenously
Vehicle:
other: 0.5% carboxymethyl cellulose (0.5% CMC) for oral administration, or 0.9% saline for intravenous administration
Details on exposure:
- Dose selection rationale: the results of a Sponsor toxicology study indicated that the low dose was without effect, and the high dose had limited toxicological or pharmacological effects.
Duration and frequency of treatment / exposure:
Duration of treatment: Single intravenous or oral dose, or after multiple daily oral doses for 7 or 15 days
Frequency of exposure: Daily
Post exposure period: Up to 168 hours
Doses / concentrations
Remarks:
Doses / Concentrations:
0, 50, 1000 mg/kg
No. of animals per sex per dose / concentration:
7 - 9 animals per sex per dose
Control animals:
other: (0.5% CMC) only, oral
Positive control reference chemical:
None
Details on study design:
STUDY ELEMENTS:
Preliminary study (PRE): groups P-1 and P-2
Absorption and excretion (AE): groups A, B, C, C-1 and D
Pharmacokinetic (PK): groups E, F, F-1 and G
Tissue distribution (TD): groups H, I, I-1 and J
Biliary excretion (BE): groups K and L
Placental transfer (PT): group M
Milk transfer (MT): group N
Qualitative whole-body autoradiography (WBA): groups O and Q
Vehicle Control: group R

Housing and feeding condition: animals were housed individually and fed rodent diet #5002 (PMI Feeds, Inc,) ad libitum except when fasted for dosing procedres. All animals received water ad libitum, provided fresh daily.
Details on dosing and sampling:
SAMPLES AND OBSERVATIONS:
Types and timing of observations and sampling regime for each study element: see Table 1.
-PRE and vehicle control: preliminary study and vehicle control animals were housed in individual metabolism cages for the separate collection of urine and feces, and expired air for preliminary study animals. Whole blood/ plasma was collected at termination. After final excreta collection, carcasses retained.
-AE: animals were housed in individual metabolism cages for the separate collection of urine and feces. Whole blood/ plasma was collected at termination. After final excreta collection, major organs and tissues, and carcasses were collected.
- PK: whole blood was collected via a jugular vein into heparinized tubes and plasma was harvested at each time point. The cellular fraction was discarded. After final collection, carcasses discarded.
- TD: whole blood and plasma from all animals was collected at termination. The major tissues and organs, and carcasses were collected from 3 animals at each sacrifice, and then excised, rinsed with saline, blotted dry, weighed, and placed on ice.
- BE: bile samples were collected in containers surround by ice. Urine and faeces were collected separately. Whole blood/plasma, major organs and tissues, and carcasses were collected at termination.
-PT: 3 animals/time point were sacrificed via exsanguination. Two whole foetuses/animal, selected tissues from 2 further foetuses/animal (placenta, amniotic fluid, blood, brain, heart, liver, lungs, kidneys, carcass), maternal tissues were collected. Tissues were excised, rinsed with saline, blotted dry, weighed, and place on ice.
- MT: milk were collected from 3 animals/time point. Pups were removed from the mothers approximately 4 hours before collection of milk. Animals received a subcutaneous injection of oxytocin before milking to stimulate lactation, and then anesthetized immediately before the start of milk collection and milk (approximately 1 mL) was collected using a specially constructed milking machine. Whole blood and plasma was collected after milk collection. Carcasses discarded.
- WBA: 1 animal/sex/time point was sacrificed. All samples, except blood, were stored at -20C. Blood was stored at approximately 5 ºC until radioanalysis. Plasma from remaining blood was taken by centrifugation.
Cage rinse, wash and wipe in the groups P-1, P-2, A, B, C, C-1, D, K and L were performed and analysed.
All samples collected were weighed.
All tissues and fluids collected were homogenised unless the entire sample was used, sampled, and then analysed, in duplicate if sample size permitted. Specific tissues were digested in NaOH before analysis. Sample weights added to the appropriate scintillant were 0.5ml trapping solution (CO2), 0.03 or 0.1g (urine), whole sample (faeces, and plasma from groups E, F, F-1 and G), 0.2g (whole blood), 0.2g (plasma from all other groups), 0.02g (bile), 0.1g (milk), 0.5g (cage wash / rinse / wipe), and 0.2 - 0.5g (tissues). Scintillation counts were automatically corrected for counting efficiency.
Statistics:
See below

Results and discussion

Preliminary studies:
See Table 2.
Treatment of the two preliminary groups with F-labelled and G-labelled dinotefuran demonstrated that the distribution of radioactivity between urine, faeces and carcass was similar, and that radioactivity in expired air amounted to 0.01 - 0.05% of administered dose. Therefore, the definitive study was performed with an approximate 1:1 ratio of both radiolabelled forms. Expired air was not collected.

Toxicokinetic / pharmacokinetic studies

Details on absorption:
See Table 3.
The total mean recovery of radioactivity ranged from 92.7 to 103% of administered dose, with 87.7 to 99.8% recovered in urine, 1.06 to 3.16% recovered in faeces, 0.62 to 6.42% recovered from the cages. The similar, and extensive, recoveries in urine following oral and intravenous administration indicate almost complete absorption of [14C]-dinotefuran from the gastrointestinal tract. Radioactivity was eliminated rapidly with 84.3 to 98.9% of administered single doses excreted in urine within 24 hours. The absorption and route and rate of elimination were not influenced by sex, dose level or dose regimen.
Details on distribution in tissues:
See Table 5.
Radioactivity was widely distributed in all tissues examined 0.5 hours after a single oral dose of 50mg/kg. At this time, only the concentrations in the kidneys (79.4ppm), stomach (67.3ppm) and urinary bladder (45.8ppm) were higher than in plasma (40.6ppm) for male. Tissue concentrations declined quickly and at 168 hours after dosing all tissues, with the exception of male skin (0.05ppm), kidneys (0.01ppm) and mammary gland (0.02ppm), were below the limits of detection (0.001ppm). All tissues were below the limits of detection 168 hours after a single intravenous dose. With the exceptions of male and female skin (0.007 and 0.014ppm), female bone (0.004ppm), female intestinal tract (0.003ppm) and female mammary gland (0.018ppm), all tissues were below the limit of detection 168 hours after 15 oral doses of 50mg/kg/day). Radioactivity was widely distributed in most tissues examined following 7 daily oral doses of 50mg/kg and after a single oral dose of 1000mg/kg. In these groups, low concentrations occurred in plasma (0.002 - 0.028ppm) and the highest concentrations occurred in female mammary gland (0.324 - 0.703ppm) and in the skin (0.193 - 0.692ppm). The results indicate that the disposition of radioactivity is similar following single or multiple dosing regimens and after low or high doses.
Details on excretion:
See Details on absorption

Metabolite characterisation studies

Metabolites identified:
yes
Details on metabolites:
Unchanged dinotefuran in urine accounted for 92.5 - 97.2% of total urine radioactivity. A group of urinary metabolites, PHP and its isomers, 446-DO and its isomers, 446-CO, 446-DO-Ac, 446-OH-Ac and 446-OH+COOH, represented 2.08 - 5.95% administered radioactivity. Other minor urine metabolites, UF, FNG and DN, each accounted for no more than 0.53% administered radioactivity. Trace amounts (< 0.1% administered radioactivity) of 9 other metabolites were also detected in urine. Unchanged dinotefuran for 0.29 to 3.57 % of total administrated radiolabel was the major component of faecal radioactivity, but numerous minor metabolites were identified, and 0.01 - 1.75% administered radioactivity represented unidentified polar metabolites. Unchanged dinotefuran for 0.52 to 0.77 % of total administrated radiolabel was the major component of bile radioactivity, and minor metabolites were similar to those found in urine and faeces. Unchanged dinotefuran was the major component of plasma radioactivity (> 80%) with possible metabolites of MNG, 446-DO-Ac and PHPs. Overall, more than 90% of the radioactivity derived from [14C]- dinotefuran is excreted as unchanged parent compound following oral or intravenous administration. Dinotefuran is the major radioactive component in most tissues examined, and less than 10% of dinotefuran is metabolised. There were no apparent differences related to treatment regimen or sex in the metabolic handling of dinotefuran. Initially, enzymatic hydroxylation on the tetrahydrofuran ring occurs to form PHP isomers, followed by further oxidation, reduction and acetylation of PHP to produce possible isomers of 446-CO, 446-DO, PHP-Ac and 446-OH+COOH. Other routes of metabolism involve desmethylation to FNG, nitro-reduction to 446-NH2 and further hydrolysis to DN and UF. The combination of these reactions at certain stages produced numerous metabolites such as UF-DM, FNG-DN, BCDN, DN-OH and isomers and DN-CO. Trace amounts of MNG, MG and MG-Ac indicate a small degree of cleavage at the C-N bond to yield the furan and guanidine moieties.

Any other information on results incl. tables

TOXIC EFFECTS AND CLINICAL SIGNS:

All animals appeared clinically healthy throughout the study, with the exception of following animals.

One animal in group E appeared pale and hypoactive between the 1- and 4-hour blood collections and recovered by the 24-hour collection. In an animal in Group F, there were difficulties in obtaining the 4-hour blood sample, and then the animal died shortly after the collection. The animals in group G appeared lethargic approximately 45 minutes to 1 hour postdose.Animals had recovered by 4 hours postdose.

PHARMACOKINETICS (PK):

See Table 4.

The mean maximum plasma concentration of [14C]-dinotefuran ranged from 40.8 to 47.4ppm at 0.25 to 0.625 hours after administration of single or repeated low oral doses. A single high oral dose produced Cmaxvalues of 566 and 471ppm in males and females, respectively, at approximately 2 hours after administration. The elimination half-life ranged from 3.64 to 16.1 hours for single and repeated low oral doses. A single high oral dose produced T1/2values of 13.8 and 15.2 hours in males and females, respectively. AUC values following single and repeated low oral doses were in the range 69.0 to 110ppm.hr, compared with values of 2660 and 2360 ppm.hr in males and females respectively after a single high oral dose. Since the ratios of dose to AUC were comparable for low and high dose levels, absorption and pharmacokinetic characteristics of [14C]- dinotefuran are considered to be linear within the dose range 50 - 1000mg/kg. BILIARY EXCRETION (BE):

See Table 6.

A small amount of radioactivity (0.58 - 0.88% dose) was detected in bile samples after single doses of either 50 or 1000mg/kg, indicating very limited enterohepatic re-circulation of radioactivity.

PLACENTAL TRANSFER (PT):

See Table 7.

Radioactivity was rapidly transferred to foetuses and rapidly distributed to the foetal tissues. Maximum foetal concentrations occurred in all tissues examined within 0.5 hours of maternal treatment. Subsequently, radioactivity declined rapidly to low levels within 4 hours. Similar concentrations occurred in maternal and foetal blood suggesting a rapid equilibration and similar tissue distribution in maternal and foetal tissues. MILK TRANSFER (MT):

See Table 8.

Radioactivity was rapidly transferred from maternal blood to the milk of lactating animals at day 12post partum. Cmaxvalues for maternal plasma and milk were 29.3 and 34.8mg equivalents/g, respectively, 0.5 hours post dose. Concentrations in milk declined rapidly to 6.51mg equivalents/g after 4 hours. Calculation of pharmacokinetic parameters gave an elimination T1/2of 1.39 hours in milk, indicating that within 14 hours of administration the expected concentration of radioactivity would be lower than the limit of detection (0.002ppm).

QUALITATIVE WHOLE-BODY AUTORADIOGRAPHY (WBA):

Whole body autoradiography after single oral doses of 50 or 1000mg/kg were consistent with the results obtained for the tissue distribution groups mentioned previously. Tissue radioactivity derived from [14C]-dinotefuran was widely distributed and highest at the first sampling interval, 0.5 hours and 1.5 hours, for 50 and 1000mg/kg, respectively. Thereafter, levels of radioactivity were declining 1.5 hours after administration of 50mg/kg and 8 hours after administration of 1000mg/kg. Elimination was almost complete after 24 hours (50mg/kg) and 72 hours after 1000mg/kg, no detectable radioactivity was apparent in either sex. The highest levels of radioactivity were generally found in the urine, followed by the gastrointestinal contents. Low levels of radioactivity were detected in the brain and gonads of both sexes after 50 or 1000mg/kg. There were no apparent sex-related or dose-related differences in the overall distribution trends.

ANALYTICS AND RADIOACTIVE COMPONENTS:

Unchanged dinotefuran in urine accounted for 92.5 - 97.2% of total urine radioactivity. A group of urinary metabolites, PHP anditsisomers, 446-DO anditsisomers, 446-CO, 446-DO-Ac, 446-OH-Ac and 446-OH+COOH, represented 2.08 - 5.95% administered radioactivity. Other minor urine metabolites, UF, FNG and DN, each accounted for no more than 0.53% administered radioactivity. Trace amounts (< 0.1% administered radioactivity) of 9 other metabolites were also detected in urine. Unchanged dinotefuranfor 0.29 to 3.57 % of total administrated radiolabelwas the major component of faecal radioactivity, but numerous minor metabolites were identified, and 0.01 - 1.75% administered radioactivity represented unidentified polar metabolites. Unchanged dinotefuranfor 0.52 to 0.77 % of total administrated radiolabelwas the major component of bile radioactivity, and minor metabolites were similar to those found in urine and faeces. Unchanged dinotefuran was the major component of plasma radioactivity (> 80%) with possible metabolites of MNG, 446-DO-Ac and PHPs. Overall, more than 90% of the radioactivity derived from [14C]- dinotefuran is excreted as unchanged parent compound following oral or intravenous administration. Dinotefuran is the major radioactive component in most tissues examined, and less than 10% of dinotefuran is metabolised. There were no apparent differences related to treatment regimen or sex in the metabolic handling of dinotefuran. Initially, enzymatic hydroxylation on the tetrahydrofuran ring occurs to form PHP isomers, followed by further oxidation, reduction and acetylation of PHP to produce possible isomers of 446-CO, 446-DO, PHP-Ac and 446-OH+COOH. Other routes of metabolism involve desmethylation to FNG, nitro-reduction to 446-NH2and further hydrolysis to DN and UF. The combination of these reactions at certain stages produced numerous metabolites such as UF-DM, FNG-DN, BCDN, DN-OH and isomers and DN-CO. Trace amounts of MNG, MG and MG-Ac indicate a small degree of cleavage at the C-N bond to yield the furan and guanidine moieties.

Table 1   Treatment schedule and sampling regime

Group

Study element

Dose

(mg/kg)

Number doses

(1 dose/day)

Route

Position of radiolabel

No. animals

(M + F)

Sampling regime

P-1

PRE

50

1a

oral

[F-14C] dinotefuran

3 + 3

Expired air: 24-hour intervals for 7 days

Urine / faeces: 0 - 6, 6 - 12, 12 - 24, 24 - 48, 48 - 72, 72 - 96, 96 - 120, 120 - 144 and 144 - 168hrs

Whole blood / plasma: at termination

Cage rinse: 0 - 24hrs

Cage wash / wipe: after final excreta collection

Termination: after final excreta collection, carcasses retained

P-2

50

1a

oral

[G-14C] dinotefuran

3 + 3

A

AE

50

1

intravenous

1:1 mixture

5 + 5

Urine / faeces: 0 - 6, 6 - 12, 12 - 24, 24 - 48, 48 - 72, 72 - 96, 96 - 120 and 120 - 144, 144 - 168hrs

Whole blood / plasma: at termination

Cage rinse: 0 - 24hrs

Cage wash / wipe: after final excreta collection

Termination: after final excreta collection, major organs / tissues + carcasses collected

B

50

1

oral

1:1 mixture

5 + 5

C

50

14b+1

oral

1:1 mixture

5 + 5

D

1000

1

oral

1:1 mixture

5 + 5

C-1

50

7

oral

1:1 mixture

5 + 5

Urine / faeces: 0 -24, 24 - 48, 48 - 72, 72 - 96, 96 - 120, 120 - 144 and 144 - 168hrs + 0 - 6, 6 - 12, 12 - 24, 24 - 48, 48 - 72, 72 - 96, 96 - 120, 120 - 144 and 144 - 168hrs

Whole blood / plasma: at termination

Cage rinse: 24 hr intervals

Cage wash / wipe: after final excreta collection

Termination: after final excreta collection, major organs / tissues + carcasses collected

E

PK

50

1

oral

1:1 mixture

5 + 5

Blood plasma: pre-dose, 0.25, 0.5, 0.75, 1.0, 1.5, 2, 4, 8, 12, 24, 48 and 72hrs

Termination: after final collection, carcasses discarded

F

50

14b+1

oral

1:1 mixture

5 + 5

F-1

50

7

oral

1:1 mixture

5 + 5

G

1000

1

oral

1:1 mixture

5 + 5

H

TD

50

1

oral

1:1 mixture

9 + 9

Whole blood and plasma: at termination

Termination: 3 animals sacrificed at 0.5, 1.5 and 4hrs after final dose, 30 major organs / tissues + carcasses collected

I

50

14b+1

oral

1:1 mixture

9 + 9

I-1

50

7

oral

1:1 mixture

9 + 9

J

1000

1

oral

1:1 mixture

9 + 9

Whole blood and plasma: at termination

Termination: 3 animals sacrificed at 1.5, 4 and 8hrs after dose, 30 major organs / tissues + carcasses collected

K

BE

50

1

bile duct

1:1 mixture

4 + 4

Urine / faeces: 0 - 6, 6 - 12, 12 - 24, 24 - 48hrs

Whole blood / plasma: at termination

Bile: 24hrs pre-dose, 0 -6, 6 - 12, 12 - 24 and 24 - 48hrs

Cage rinse: 0 - 24hrs

Cage wash / wipe: after final excreta collection

Termination: after final excreta collection, major organs / tissues + carcasses collected

L

 

1000

1

bile duct

1:1 mixture

4 + 4

M

PT

50

1

oral

1:1 mixture

0 + 9c

Whole blood and plasma: at termination

Termination: 3 animals/time point sacrificed at 0.5, 1.5 and 4hrs after dose, 2 whole foetuses/animal, selected tissues from 2 further foetuses/animal (placenta, amniotic fluid, blood, brain, heart, liver, lungs, kidneys, carcass), maternal tissues collected

N

MT

50

1

oral

1:1 mixture

0 + 9d

Milk: 0.5, 1.5 and 4hrs

Whole blood and plasma: at termination

Termination: 3 animals/time point sacrificed at 0.5, 1.5 and 4hrs after milk collection, carcasses discarded

O

WBA

50

1

 

 

oral

1:1 mixture

4 + 4

Termination: one animal/sex/time point sacrificed at 0.5, 1.5, 4 and 24hrs post-dose and subjected to qualitative WBA

Q

1000

1

oral

1:1 mixture

4 + 4

Termination: one animal/sex/time point sacrificed at 1.5, 4, 8 and 72hrs post-dose and subjected to qualitative WBA

R

Vehicle control

(0.5% CMC)

0

1

oral

 

2 + 2

Urine / faeces: 0 - 6, 6 - 12, 12 - 24, 24 - 48, 48 - 72, 72 - 96, 96 - 120, 120 - 144 and 144 - 168hrs

Whole blood / plasma: at termination

Termination: after final excreta collection, carcasses retained

aone group treated with[F-14C]-dinotefuran, one group treated with[G-14C]-dinotefuran;b14 days non-radiolabelled treatment followed by one radiolabelled dose; pregnant females on day 10 of gestation at first dose;cpregnant females at approximately day 18 of gestation;dlactating females ca. 12 dayspost partum; PRE preliminary study; AE absorption and excretion; PK pharmacokinetic; TD tissue distribution; BE biliary excretion; PT placental transfer; MT milk transfer; WBA whole-body autoradiography (qualitative)

 

Table 2. Total recovery of radioactivity at 168 hours (preliminary study)

Sex

Test substance

% administered dose in:

Urine

Faeces

Cage

Expired air

Carcass

Total

Male

[F-14C]-dinotefuran

90.3

1.39

5.73

0.01

0.09

97.5

[G-14C]-dinotefuran

90.6

4.02

2.97

0.05

0.10

97.8

Female

[F-14C]-dinotefuran

82.0

7.32

8.23

0.02

0.44

98.0

[G-14C]-dinotefuran

93.5

1.22

2.51

0.05

0.08

97.3

 

Table 3. Total recovery of radioactivity at 168 hours (main study)

Sex

Dose / frequency / route

(mg/kg x no. doses)

% administered dose in:

Urine

Feces

Cage

Tissues & carcass

Total

Male

50 x 1 i.v.

96.7

1.06

1.90

0.09

99.7

50 x 1 oral

98.9

1.66

1.33

0.06

102

50 x 15 oral

96.8

1.54

2.83

0.06

101

50 x 7 oral

98.3

1.85

2.42

0.10

103

1000 x 1 oral

90.1

2.15

2.52

0.10

94.7

Female

50 x 1 i.v.

96.6

1.26

1.42

0.05

99.2

50 x 1 oral

99.8

1.19

0.62

0.08

102

50 x 15 oral

89.7

3.16

6.42

0.21

99.3

50 x 7 oral

95.8

1.53

4.88

0.10

102

1000 x 1 oral

87.7

2.39

2.67

0.06

92.7

 

Table 4. Pharmacokinetic parameters calculated for [14C]-dinotefuran

Sex

Dose/ frequency/ route

(mg/kg x no. doses)

Mean values for:

Cmax(ppm)

Tmax

(hrs)

T1/2

 (hrs)

AUC0-T

(ppm.hour)

AUC0

(ppm.hour)

Male

50 x 1/ oral

40.8

0.50

3.64

83.3

83.3

50 x 15/ oral

47.4

0.45

5.65

92.1

92.1

50 x 7 oral

41.5

0.63

6.28

91.2

91.2

1000 x 1 oral

566

2.10

13.8

2660

2660

Female

50 x 1 oral

45.6

0.25

7.86

110

110

50 x 15 oral

42.2

0.38

6.89

76.0

76.0

50 x 7 oral

43.8

0.31

16.1

69.0

69.2

1000 x 1 oral

471

2.00

15.2

2360

2370


Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): no bioaccumulation potential based on study results
It is concluded that the absorption, distribution, metabolism and elimination of [14C]-dinotefuran are unaffected by sex within dosing groups and also no apparent differences among the examined dosing regimens.