Registration Dossier

Toxicological information

Basic toxicokinetics

Currently viewing:

Administrative data

Endpoint:
basic toxicokinetics
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Peer reviewed, scientifically fully acceptable and sufficiently documented publication.
Cross-reference
Reason / purpose:
reference to same study

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1996

Materials and methods

Objective of study:
distribution
excretion
metabolism
Test guidelineopen allclose all
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 417 (Toxicokinetics)
Qualifier:
equivalent or similar to
Guideline:
EU Method B.36 (Toxicokinetics)
Principles of method if other than guideline:
The subacute distribution, metabolism and excretion of 14C-radiolabelled DCDPS was investigated in adult male Fischer 344 rats after oral gavage administration. The test animals were investigated in two branches.
Two assays were performed:
(test #1) Dose dependency was investigated in the 7-day repeat dosing experiment where DCDPS was dosed at 1, 10, and 100 mg/kg bw/day.
(test #2) Time dependency was observed in the 2, 3 and 5 week repeat dosing experiment where the only dose applied was 10 mg/kg bw for 5 days/week.
Samples of cumulated and 72-h urine and faeces were examined in test #1 solely, furthermore enzyme activities (EROD, benzphetamine N-demethylase) and the CYP content were determined. In test #2 excreta were collected during the exposure.
In both assays blood and several tissues were examined at 72h after end of the 7 days treatment or at week 2, 3, and 5 respectively.
GLP compliance:
yes
Remarks:
all NTP studies were conducted under GLP

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): p,p'-dichlorodiphenyl sulfone (DDS)
- Analytical purity: 98% supplied by Aldrich Chemical Company Inc, Milwaukee, WI, U.S.A.
- Radiochemical purity: 96% as determined by reversed phase HPLC
- Specific activity: 6.75 Ci/mol supplied by NEN Research Products, Boston, MA, U.S.A.
- Locations of the label: Uniformly labelled 14C[DCDPS]
- Reference material 2-Hydroxy 4,4' - DCDPS synthesized according to S.A. Agripat, british Patent 1136514 (1968)
Radiolabelling:
yes
Remarks:
, uniformly labelled 14C[DCDPS] 6.75 Ci/mol supplied by NEN Research Products (Boston, MA, U.S.A.)

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories Inc, Raleish, NC, U.S.A.
- Age at study initiation: Adult
- Diet: Purina Rodent Chow (no. 5002) ad libitum
- Water: tap water ad libitum

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
castor oil
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: Formulations contained 1-3 μCi radiolabel, an appropriate amount of unlabeled DCDPS, and Emulphor EL-620 (castor oil, a polyethoxylated vegetable oil, GAF Corp., New York, NY, U.S.A.) in a volume of 5 mL/kg bw.


Duration and frequency of treatment / exposure:
Daily treatment and 3 d (72 h) post treatment observation in the 7-day repeat dosing experiment (test #1)
5 days/week treatment in the 2, 3 and 5 week repeat dosing experiment (test #2)
Doses / concentrations
Remarks:
Doses / Concentrations:
7-day repeat dosing experiment (test #1): 1, 10, 100 mg/kg bw/day
2, 3 and 5 week repeat dosing experiment (test #2): 10 mg/kg bw on 5 days a week

Post treatment observation 3 d (72 h)
No. of animals per sex per dose:
4
Control animals:
no
Details on dosing and sampling:
PHARMACOKINETIC STUDY
- Excretion was studied only in 7-day repeat dose experiment (test #1).
- Radioactivity in each sample was determined using Packard Tricarb 1500 Liquid Scintillation Analyzer (Packard Instrument Company).

7-day repeat dose experiment (test #1)
- Tissues and body fluids sampled: Adipose tissues (three samples), Blood, Liver, Muscle (trapezius, abdominal, and hindleg), Skin (three samples), Faeces and Urine (collected using metabolism cages).
- Time and frequency of sampling: Urine and faeces were collected and pooled from the experimental start until the end of the 7-days dosing and 0-72 hrs after adiministration of the last daily dose; tissues were analyzed 72 h after the end of the experiment.

2-, 3- and 5-week experiment (test #2)
- Time and frequency of sampling: Tissues were collected after week 2, week 3, and the end of the experiment, i.e. after 5 weeks.
- Tissues and body fluids sampled: Adipose tissues (three samples), Blood, both Kidneys, Liver and Skin (three samples)



METABOLITE CHARACTERISATION STUDIES (analysis in test #1 only)
- Tissues and body fluids sampled: urine and faeces
- Time and frequency of sampling: at day 7 to 10, i.e. collected 0-72 h after end of 7 days oral administration
- From how many animals: Samples were pooled from 4 animals
- Method type(s) for identification: GC/MS, 1H-NMR, HPLC
- Limits of detection and quantification: No data in the publication

TREATMENT FOR CLEAVAGE OF CONJUGATES: ß-glucuronidase, sulfatase

INDUCTION STUDIES (in test #1 only):
- livermicrosomes were prepared from sacificed animals. CYP-content, and benzphetamine N-demethylase and EROD activities were assayed.
Statistics:
In the publication no information on the applied statistical procedures is given.

Results and discussion

Main ADME resultsopen allclose all
Type:
distribution
Results:
apparent tissue steady state after ~2-3 weeks (test #2); tissue residues decreased with increased dose (63, 41, 31% at 1, 10, 100 mg/kg/d, respectively) (test #1) and with duration (28, 23, 10% after 2, 3, 5 wks of treatment, respectively) (test #2).
Type:
metabolism
Results:
main metabolites: 3-hydroxy-DCDPS and its glucuronide; up to 5 minor non-identified metabolites; induced its own metabolism
Type:
excretion
Results:
urine: 10.7 to 21.8% of total dose, faeces: 19.9 to 32.6% of total dose, increasing with dose (test #1). In 3- and 5-wk repeat dosing studies ca. 100% of administered dose in final week (test #2).

Toxicokinetic / pharmacokinetic studies

Details on distribution in tissues:
DCDPS was rapidly distributed in the tissues. In the 7-day repeat experiment (test #1) the percentage of total dose in tissues decreased from 62.9 to 30.9% with increasing dose levels (from 1 to 100 mg/kg bw/d). The dose retained in individual organs declined with increasing dose in adipose (41.0 to 19.7%), muscle (9.2 to 3.6%) and skin (10.9 to 3.8%), but remained constant in liver (1.2%) and blood (0.2%).
In the 2-5 week repeat dosing studies (test #2) the percentage of total dose in tissues decreased (28.3 to 10.1%) with the duration of exposition.
In test #2 it was established that radiochemical content in adipose peaked at 3 weeks (312±20 µg-eq/g tissue), and declined by 5 weeks (231±33 µg-eq/g tissue). DCDPS equivalents in the liver, kidney and skin were near maximum after approximately 2 weeks (20±2, 7.1±1.2 and 24±8 µg-eq/g tissue, respectively) and remained relatively constant thereafter (24±4, 9.4±1.4, 23±4 µg-eq/g tissue, respectively, after 5 weeks).
Details on excretion:
DCDPS-derived radioactivity was excreted primarily in faeces and to a lesser extent in urine.
In test #1 dose dependency was observed. The total cumulative excretions over 10 days were 10.7, 13.8 and 21.8 % (urine), and 19.9, 35.0 and 32.6% (faeces) with increasing doses of 1, 10 and 100 mg/kd bw/d. Accordingly only 30.6% of the lower dose versus 48.8 and 54.4% of the two higher doses were observed in excreta.
In test #2 the amount excreted during the final week was equivalent to 99% and 106% of the dose equivalent administered during that period, indicating that steady state had been reached after approximately 2-3 weeks of repeat dosing.

Metabolite characterisation studies

Metabolites identified:
yes
Details on metabolites:
Three metabolite fractions were obtained: 1) the phenolic metabolite 3-hydroxy-4,4'-dichlorodiphenyl sulfone, 2) its glucuronide, 3) metabolite fraction A (comprised of up to five components, each containing < 1% of the administered dose).
Administration of 100 mg/kg bw/day resulted in a pattern of excretion very similar to that seen at 10 mg/kg/day or about 10 times the total amount of DCDPS metabolized with no apparent saturation of any process involved (test #1).

Any other information on results incl. tables

7-day repeat dosing experiment (test #1)

Disposition of radioactivity at day 10

i.e. 72 h after final oral dose administrated in a 7-days repeat dosing of (14C) DCDPS to male F-344 ratsa

Tissues

% Dose in Total Tissue

1 mg/kg bw

10 mg/kg bw

100 mg/kg bw

Adipose

41.0±4.9

27.5±1.1

19.7±3.9

Blood

0.2±0.0

0.2±0.0

0.2±0.1

Liver

1.2±0.2

1.2±0.0

1.2±0.4

Muscle

9.2±1.2

6.1±2.8

3.6±0.6

Skin

10.9±0.5

5.8±1.2

3.8±1.4

Total in tissues

62.9±6.5

41.1±3.6

30.9±3.3

Cumulative Excretion (over 10 days)
 Urine

10.7±2.7

 13.8±4.3  21.8±6.4
 Faeces 19.9±3.1  35.0±1.2  32.6±5.4
 Total in Excreta  30.6±2.0  48.8±5.1  54.4±6.2
          
 Total recovery  93.5±6.5  89.9±1.2  85.3±3.6

Profile of metabolites appearing in the urine and feces at day 7 to 10

i.e. of rats collected 0-72 h after end of 7 days oral administration of (14C) DCDPS to male F-344 rats

Dose

(mg/kg bw)

Sample

% of Dose appearing as

Glucuronide Conjugate

Metabolite A

(chromatographic peak)

Aglycone

DCDPS

1

Urine

1.22

0.32

1.50

ND

Feces

0.55

0.61

5.39

1.41

Total

1.77

0.93

6.89

1.41

10c

Urine

1.00

0.44

3.00

0.079

Feces

1.17

1.44

11.30

1.24

Total

2.17

1.88

14.3

1.32

100c

Urine

1.43

0.78

4.07

ND

Feces

0.90

0.35

8.86

0.94

Total

2.34

1.13

12.9

0.94

a Values are means ± SD for 4 rats (n = 4)

ND = not detected

c The amount of unmetabolized DCDPS in faeces decreased by about one-half after repeat administration compared with the single doses (see Mathews 1996, rat single oral), while the representation of the glucuronide and its aglycone was equal or somewhat greater.

However the authors state that the conversion of DCDPS to two metabolites (aglycone and glucuronide) was also doubled as the dose level in the 7-day repeat dosing was increased from 1 to 10 and 100 mg/kg bw/day it was de facto doubled solely for the aglycone (6.89, 14.3, and 12.9%), while it was increased by 32% for the Glucuronide Conjugate (1.77, 2.17, and 2.34% respectively).

2, 3 and 5 week repeat dosing experiment (test #2)

Time course of disposition of radioactivity after repeat oral adminsitration of (14C) DCDPS (10 mg/kg bw) to male F-344 ratsa

Tissues

Distribution in tissues
% Dose in Total Tissue

2 weeks

3 weeks

5 weeks

Adipose

19.6±1.4

15.3±1.01

6.72±0.98

Blood

0.125±0.01

0.125±0.014

0.0837±0.0084

Kidney

0.0556±0.0074

0.0456±0.0088

0.0276±0.0036

Liver

0.939±0.117

0.685±0.167

0.483±0.061

Skin

4.23±1.42

3.90±0.91

1.61±0.31

Total in tissues

28.3±3.3

22.8±2.0

10.1±1.5

 

µg-eq/g tissue

 

Adipose fat

265±19

312±20

231±33

Blood

2.3±0.2

3.4±0.3

3.9±0.4

Kidney

7.1±1.2

8.9±1.7

9.4±1.4

Liver

20±2

21±5

24±4

Skin

24±8

33±8

23±4

a Values are means ± SD for 4 rats (n = 4)

Accordingly fat-to-liver ratios after 2, 3, and 5 weeks were 13, 15, and 10 respectively.

Induction Studies (test #1)

The EROD activity in animals receiving 10 mg/kg bw/day was up to twice that of animals receiving 1 mg/kg bw/day or vehicle control suggesting that increased metabolism occurs with increasing concentration, but there was no effect in the 100 mg/kg bw/day group. The P450 content was increased by 60% in the 100 mg/kg bw/day group.

Applicant's summary and conclusion

Conclusions:
An apparent steady state after repeated dose application is found in the order of 2 weeks.
Executive summary:

The subacute absorption, distribution, metabolism and excretion of 14C-radiolabelled DCDPS were investigated in adult male Fischer 344 rats after oral gavage administration. The experimental approach is similar to OECD TGD 417 standards and regarded valid and conclusive.

Two assays were performed:

(test #1) dose dependency was investigated in the 7-day repeat dosing experiment where DCDPS was dosed at 1, 10, and 100 mg/kg bw/day.

(test #2) time dependency was observed in the 2, 3 and 5 week repeat dosing experiment where the only dose applied was 10 mg/kg bw for 5 days/week. Samples of cumulated and 72-h urine and faeces were examined in test #1 solely, furthermore enzyme activities (EROD, benzphetamine N-demethylase) and the CYP content were determined. In test #2 excreta were collected during the exposure. In both assays blood and several tissues were examined at 72h after end of the 7 days treatment or at week 2, 3, and 5 respectively.

Absorption: In test #1 the percentage of total dose in tissues decreased from 62.9 (1 mg/kg bw/day) to 30.9% (100 mg/kg bw/day). In test #2 the percentage of total dose in tissues decreased (28.3 to 10.1%) with the duration of exposition.

Distribution: DCDPS was rapidly distributed in the tissues. In test #1 the percentage of total dose in most tissue decreased with increase in dosing concentrations, i.e. adipose (41.0 to 19.7%), muscle (9.2 to 3.6%) and skin (10.9 to 3.8%), but remained constant in liver (1.2%) and blood (0.2%). 'The total percentage in tissue decreased from 63 to 31%. In the 2-5 week repeat dosing studies (test #2) the percentage of total dose in tissues decreased (28.3 to 10.1%) with the duration of exposition.

In test #2 it was established that radiochemical content in adipose peaked at 3 weeks (312±20 µg-eq/g tissue), and declined by 5 weeks (231±33 µg-eq/g tissue). DCDPS equivalents in the liver, kidney and skin were near maximum after approximately 2 weeks (20±2, 7.1±1.2 and 24±8 µg-eq/g tissue, respectively) and remained relatively constant thereafter (24±4, 9.4±1.4, 23±4 µg-eq/g tissue, respectively, after 5 weeks).

Metabolisation: Three metabolite fractions were obtained: 1) the phenolic metabolite 3-hydroxy-4,4'-dichlorodiphenyl sulfone, 2) its glucuronide, 3) metabolite fraction A (comprised of up to five components, each containing < 1% of the administered dose).

Administration of 100 mg/kg bw/day resulted in a pattern of excretion very similar to that seen at 10 mg/kg/day or about 10 times the total amount of DCDPS metabolized with no apparent saturation. DCDPS induced its own metabolism. The P450 content was increased by 60% in the 100 mg/kg bw/day group, which indicates increased enzyme production.

The EROD activity in animals receiving 10 mg/kg bw/day (test #1) was up to twice that of animals receiving 1 mg/kg bw/day or vehicle control suggesting that increased metabolism occurs with increasing concentration, but there was no effect in the 100 mg/kg bw/day group. Thus the EROD result is considered not reliable.

Excretion: DCDPS-derived radioactivity was excreted primarily in faeces and to a lesser extent in urine. In test #1 dose dependency was observed. The total cumulative excretions over 10 days were 10.7, 13.8 and 21.8 % (urine), and 19.9, 35.0 and 32.6% (faeces) with increasing dose. Accordingly 30.6% of the lower dose versus 48.8 and 54.4% of the two higher doses were observed in excreta.

In test #2 the amount excreted during the final week of the 3- and 5 -week repeat dose study was equivalent to 99% and 106% of the dose administered during that period, indicating that steady state had been almost reached after approximately 2-3 weeks of repeated dosing.