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Reference
Endpoint:
basic toxicokinetics in vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2000-08-29 to 2001-01-23
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Objective of study:
other: The objective of this study was to evaluate the plasma pharmacokinetics of the test substance, 14C Diphenylmethane-4,4'-di-N-butylurea, after single administration by the oral and cutaneous routes in rats. In addition, the excretion balance was investigat
Qualifier:
no guideline available
Principles of method if other than guideline:
A total of eighty Sprague-Dawley rats (40 males and 40 females), weighing an average 194 g and 166 g for the males and females respectively (7 weeks old), were divided into five groups and each received a single administration of the radiolabelled test substance, 14C Diphenylmethane-4,4'-di-N-butylurea, by the oral or cutaneous route (as suspension in 1 % aqueous carboxymethylcellulose) as follows:
- group 1 (nine rats/sex): oral gavage at a dose-level of 150 mg/kg bw;
- group 2 (nine rats/sex): oral gavage at a dose-level of 1000 mg/kg bw;
- group 3 (nine rats/sex): topical application at a dose-level of 150 mg/kg bw;
- group 4 (nine rats/sex): topical application at a dose-level of 1000 mg/kg bw;
- group 5 (four rats/sex): oral gavage at a dose-level of 150 mg/kg bw,
Groups 1 to 4 were used for plasma pharmacokinetics, whilst group 5 was used for excretion balance.
GLP compliance:
yes
Radiolabelling:
yes
Species:
rat
Strain:
other: Sprague-Dawley rats; Crl CD (SD) IGS BR; Caesarian Obtained, Barrier Sustained-Virus Antibody Free (COBS-VAF)
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River UK; Margate, England;
- Age at study initiation: 7 weeks old,
- Weight at study initiation: males: mean 194 g (range: 180 to 217 g); females: mean: 166 g (range: 140 to 202 g);
- Fasting period before study: overnight;
- Housing: for plasma pharmacokinetics (group 1 to 4) in threes in suspended wire-mesh cages;
- Individual metabolism cages: the animals of the excretion balance (group 5) were housed in plastic metabolism cages;
- Diet: ad libitum; A04 C pelleted diet (group 1 to 4), powdered (group 5); Supplier: UAR, Villemoisson, Epinay-sur-Orge, France;
- Water: tap water filtered (0.22 micron filter) ad libitum;
- Acclimation period: 7days (group 3 and 4); 6 days (group 1,2 and 5);


ENVIRONMENTAL CONDITIONS
- Temperature: 21 +/- 2 °C;
- Humidity: 50 +/- 20 % R.H.;
- Air changes: 12 cycles/hour of filtered, non-recycled air;
- Photoperiod: 12 hours light/12 hours dark;
Route of administration:
oral: gavage
Vehicle:
other: 1 % aqueous carboxymethylcellulose
Details on exposure:
Oral administration (groups 1,2,and 5):
Test dosage forms were administered by gavage (under a dosage volume of 5 mL/kg) using a plastic syringe with a metal probe.
Topical administration (groups 3 and 4):
The day before dosing, on the interscapular/upper back region of the animals, an area of about 10 % of the whole body surface, i.e. 25 cm2 for a rat of 200 g bw and 30 cm2 for a rat of 250 g bw) was clipped free of hair.
On the day of dosing, 20 µL of the test substance dosage form was spread evenly and thinly over each cm2 of the exposed skin using a spatula. The test site was then protected with a gauze pad and lightweight semi-occlusive dressing.
Duration and frequency of treatment / exposure:
Oral dosage: one single dose;
Topical treatment: 24 hours,
Remarks:
Doses / Concentrations:
For doses/concentrations, see Sect. "any other information on materials and methods incl. tables"
No. of animals per sex per dose / concentration:
Oral administration:
150 mg/kg bw: 9 males / 9 females (plasma pharmacokinetics);
1000 mg/kg bw: 9 males / 9 females (plasma pharmacokinetics);
150 mg/kg bw: 4 males / 4 females (excretion balance);

Topical administration:
150 mg/kg bw: 9 males / 9 females (plasma pharmacokinetics);
1000 mg/kg bw: 9 males / 9 females (plasma pharmacokinetics);
Control animals:
no
Positive control reference chemical:
NA
Details on study design:
Groups 1 to 4 were used for plasma pharmacokinetics, whilst group 5 was used for excretion balance.
For topical application, the dosage forms were applied for a 24-hours period (during which the site was protected with light bandages) over 10 % of the body surface area; thereafter the bandages were removed and the site washed.
Constant radioactive doses of 2.2 and 3.7 MBq/kg were used for the oral and cutaneous routes, respectively.
Details on dosing and sampling:
For groups 1 to 4:
Blood samples were collected (from 3 rats/sex/time point) under isoflurane anaesthesia, as follows:
- oral route: 0.25; 0.5; 1; 2; 4, 8; 12; 24 and 48 hours post gavage;
- cutaneous route: 4; 8 and 24 hours post-application and 1; 2, 4, 8; 12 and 24 hours post-removal of the substance.
For group 5:
Weighed urine, feces, and cage-wash were collected predose, and then over the periods 0-24, 24-48, 48-72, 72-120 and 120-168 hours post-gavage.

After final samplings, all animals were killed and the carcasses (including those from group 5) discarded.
The blood samples (after removal of a portion for hematocrit and radioactivity measurements at 3 selected time-points/route) were centrifuged to obtain plasma. Each biological sample was analyzed for total radioactivity after the appropriate preparation, and mass balance calculations were performed for group 5.
During the study, the animals were observed for clinical signs, morbidity and mortality.
Body weight was recorded pre-dosing, the day of treatment and at sacrifice (group 5).

Statistics:
The number of animals selected was chosen to be high enough to allow statistical calculations but with attention to minimize animal use as far as is compatible with the scientific objectives of the study.
Preliminary studies:
Not performed
Details on absorption:
Following both oral gavage and topical application (24-hour exposure period) at the dose-levels of 150 and 1000 mg/kg bw, the plasma radioactivity levels were essentially all non-quantifiable, suggesting very poor systemic absorption of the test substance and/or metabolites. The results were homogenous for both sexes/route/dose-level.
Details on distribution in tissues:
No distribution in tissues has been investigated.
Details on excretion:
Following oral gavages at 150 mg/kg bw, the radioactivity was quickly (> 99 % of fecal recovered dose within 48 hours) and almost exclusively (97.7 / 95.3 % of the total dose for males/females) eliminated in the feces.
The combined recoveries in urine and cage wash were respectively (males/females 0.17 / 0.92 %, giving a total mass balance of 97.9 / 96.2 % over the 168-hour period.
The urine data (in view of the plasma data) would indicate very poor absorption of the test substance and/or metabolites.
Metabolites identified:
not specified
Details on metabolites:
No metabolites have been identified in this study.

Results

Plasma and blood pharmacokinetics (groups 1 to 4)

Following oral and cutaneous dosing at both the low and high dose-levels, all mean plasma levels were essentially below quantifiable limits ( 0.23/1.53 μg-eq/g for the low/high dose-level oral route and 0.14 or 0.068/0.91 or 0.45 μg-eq/g for the low/high dose-level cutaneous route) for all animals. Where levels were quantifiable (i.e. 0.098 μg-eq/g for males and 0.164 μg-eq/g for females at 24 hours post-washing given 150 mg/kg topically), the values can be considered to be effectively at the quantification limits. All blood values were non-quantifiable (> 7.56 Bq/g for both dose-levels and routes).

In view of the above data, no pharmacokinetic data modelling was possible.  

Excretion balance (group 5)

Following oral gavage of the isotopic mixture at 150 mg/kg, the mean (±standard deviation) total cumulative recovery of the radioactive dose in the excreta in a 168-hour period was complete at 97.9±2.5% for males and 96.2±3.3% for females. The radioactivity was eliminated rapidly (essentially all within 48 hours) and almost exclusively in the feces (a mean 97.7±2.5% for males and 95.3±3.2% of the administered dose for the males and females, respectively).

For urine, the percentage of the radioactive dose found was extremely low at only 0.032±0.001 % (males) and 0.047±0.018 % (females); this finding, in view of the plasma data, would suggest that the orally given test substance and/or metabolites were not absorbed. For cage wash, the recovery of radioactivity was also low (mean±0.06% and 0.87±1.20% of the dose for the males and females, respectively) indicating that there were no cross-contamination problems. The excretion patterns were homogenous for all animals/sexes.  

Mortality and clinical signs

No mortality, morbidity or clinical signs were observed.

Conclusions:
The plasma pharmacokinetics (after oral and topical administration) and elimination of radioactivity in excreta (after oral dosing) of 14C-Diphenylmethane-4,4'-di-N-butylurea (PATE HAT séchée) was investigated. The study showed that:

- very poor systemic absorption of the test substance and/or metabolites;
- the excretion in feces was very quickly and almost exclusively.

The urine data would indicate very poor absorption of the test substance and/or metabolites.
Based on these study results, bioaccumulation of PATE HAT séchée is considered to be not very likely.
Executive summary:

The pharmacokinetic behaviour of PATE HAT séchée was investigated with a 14C radioactive labelled compound of the substance. The plasma pharmacokinetics of the substance after oral and dermal application and the elimination of radioactivity after oral dosing were measured.

The study showed

- very poor systemic absorption of the test substance and/or metabolites;

- very quick and almost exclusive excretion in feces.

Urine data indicated also very poor absorption of the test substance and/or metabolites.

Based on these results, bioaccumulation of PATE HAT séchée is considered to be not very likely.

Description of key information

Based on the results of a biokinetic study in vivo, bioavailability of HAT ISO is very limited, with oral administered substance mainly excreted via faeces and little absorption through skin. Bioaccumulation of HAT ISO was considered unlikely.

Key value for chemical safety assessment

Bioaccumulation potential:
no bioaccumulation potential

Additional information

The pharmacokinetic behaviour of HAT ISO was investigated with a 14C radioactive labelled substance. The plasma pharmacokinetics of the substance after oral and dermal application and the elimination of radioactivity after oral dosing were measured.

The study showed:

- very poor systemic absorption of the test substance and/or metabolites;

- very quick and almost exclusive excretion in feces.

Urine data indicated also very poor absorption of the test substance and/or metabolites.

Based on these results, bioavailability of HAT ISO is limited, with oral administered substance mainly excreted via faeces and little absorption through skin. Bioaccumulation of HAT ISO was considered unlikely.