3-anilino-5-methyl-5-(4-phenoxyphenyl)-1,3-oxazolidine-2,4-dione;famoxadone (ISO)

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1995

Report date:

1995

Reference 2

Reference Type:

study report

Title:

Unnamed

Year:

1996

Report date:

1996

Reference 3

Reference Type:

study report

Title:

Unnamed

Year:

1999

Report date:

1999

Reference 4

Reference Type:

study report

Title:

Unnamed

Year:

1999

Report date:

1999

Materials and methods

Objective of study:

absorption

distribution

excretion

metabolism

Test guideline

Qualifier:

according to guideline

Guideline:

EPA OPP 85-1 (Metabolism and Pharmacokinetics)

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

5-methyl-5-(4-phenoxyphenyl)-3-(phenylamino)-1,3-oxazolidine-2,4-dione

EC Number:

603-520-1

Cas Number:

131807-57-3

Molecular formula:

C22H18N2O4

IUPAC Name:

5-methyl-5-(4-phenoxyphenyl)-3-(phenylamino)-1,3-oxazolidine-2,4-dione

Test material form:

solid

Specific details on test material used for the study:

Radioactive test substance
[14C-POP]DPX-JE874
Lot #: 2675-268
Radiochemical purity: >98%
Specific activity: 22.3 mCi/mmole

[14C-PA]DPX-JE874
Lot #: 2868-107
Radiochemical purity: >98%
Specific activity: 20.5 mCi/mmole

Non-Radioactive test substance
DPX-JE874
Lot # DPX-JE874-133 (Drum 10)
Purity: >96%

Radiolabelling:

yes

Test animals

Species:

rat

Strain:

other: Crl:CD/BR ( Sprague-Dawley) albino

Details on species / strain selection:

Crl:CD/BR rats were used for this study because they have been used in the subchronic and chronic toxicology studies.

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Inc., Portage, Michigan
- Age at study initiation: Males: 7-8 weeks; Females: 9-10 weeks; Multiple dose study: 6-8 weeks
- Weight at study initiation: The average body weight 201 ± 18 g
- Housing: Prior to dosing, rats were housed individually in stainless steel cages for a minimum period of 7 days. After dosing with [14C]test substance, animals in the pilot group were housed individually in glass metabolism chambers designed for the separate collection of urine, feces and expired air. Polycarbonate metabolism chambers and stainless steel cages with raised wire mesh floors were used when the monitoring of 14CO2 in the expired air was not required (all groups except the pilot group). The animals receiving multiple daily oral doses were housed individually in stainless steel cages during the first week of the nonradiolabeled test substance dosing. These animals were then transferred to polycarbonate metabolism chambers for the collection of excreta during the remaining nonradiolabeled test substance dosing regimen. Each animal was transferred to a second (clean) polycarbonate metabolism chamber immediately after radiolabeled test substance dosing.
- Diet: ad libitum (except for an overnight predose fast prior to administration of radiolabeled material)
- Water: Tap water, ad libitum
- Acclimation period: 7 days

ENVIRONMENTAL CONDITIONS
- Temperature: 20 ± 2°C
- Humidity: 40-70%
- Air changes: 10-15 per hr
- Photoperiod: 12 hrs dark /12 hrs light

Administration / exposure

Route of administration:

oral: unspecified

Vehicle:

other: 1% sodium carboxymethyl cellulose/0.01 M ammonium acetate

Details on exposure:

Oral doses (5 and 100 mg/kg) were prepared as a suspension in 1% sodium carboxymethyl cellulose in 0.01 M ammonium acetate/HPLC grade water.

Duration and frequency of treatment / exposure:

Each rat received a single oral dose of either [14C-PA]test substance or [14C-POP]test substance.
In the case of the multiple dose group (Group G), the radiolabeled dose was preceded by 14 consecutive daily doses of non-radiolabeled test substance.

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

100 mg/kg bw/day

Remarks:

Group P (Pilot)
[14C-PA]test substance

Doses / concentrations 2

Dose / conc.:

100 mg/kg bw/day

Remarks:

Group P (Pilot)
[14C-POP]test substance

Doses / concentrations 3

Dose / conc.:

5 mg/kg bw/day

Remarks:

Group A (Kinetics)
[14C-PA]test substance

Doses / concentrations 4

Dose / conc.:

100 mg/kg bw/day

Remarks:

Group B (Kinetics)
[14C-POP]test substance

Doses / concentrations 5

Dose / conc.:

100 mg/kg bw/day

Remarks:

Group C (Kinetics)
[14C-PA]test substance

Doses / concentrations 6

Dose / conc.:

5 mg/kg bw/day

Remarks:

Group D (Metabolism)
[14C-PA]test substance

Doses / concentrations 7

Dose / conc.:

100 mg/kg bw/day

Remarks:

Group E (Metabolism)
[14C-POP]test substance

Doses / concentrations 8

Dose / conc.:

100 mg/kg bw/day

Remarks:

Group F (Metabolism)
[14C-PA]test substance

Doses / concentrations 9

Dose / conc.:

5 mg/kg bw/day

Remarks:

Group G (Metabolism)
[14C-PA]test substance

Doses / concentrations 10

Dose / conc.:

5 mg/kg bw/day

Remarks:

Group H (Distribution)
[14C-PA]test substance

Doses / concentrations 11

Dose / conc.:

100 mg/kg bw/day

Remarks:

Group I (Distribution)
[14C-PA]test substance

No. of animals per sex per dose / concentration:

Group P*: 2/sex
Group A, B, C, H*, I*: 4/sex
Group: D, E, F, G: 5/sex
Group J (control): Minimum 2/sex
(*Includes 2 groups)

Control animals:

yes, concurrent vehicle

Details on study design:

Two different test substances were examined. [14C]test substance was labeled with Carbon-14 at the phenoxyphenyl and phenylamino ring moieties. [14C]test substance was administered at the following target dose levels: Oral High Dose: 100 mg/kg & Oral Low Dose: 5 mg/kg.
The high dose level was chosen on the basis that it was a level at which slight toxicological effects could be expected. The low dose level corresponds to an approximate no-effect level.
This study involved single oral (low and high dose level) and multiple oral (low dose level) dose administrations. The target radioactive dose to each animal from the main treatment groups was approximately 30-50 µCi.

Details on dosing and sampling:

- Tissues and body fluids sampled: Urine, faeces, expired air, blood, plasma and tissues (kidneys, liver, fat, gonads, uterus, muscle, heart, lungs, spleen, brain, bone, bone marrow, adrenals, thyroid, skin, GI tract and the remaining carcass)

Statistics:

Statistical comparisons were performed using Student's t-test.

Results and discussion

Preliminary studies:

Results of Pilot study:
The 14C-radiolabel is stable at both the phenoxyphenyl and phenylamino portions of the parent molecule, and therefore, expired air of the treated animals need not be collected/monitored in the main treatment groups.
A termination time of 120 hours would be sufficient to ensure that ≥ 90 % of the administered radioactive dose is excreted.
Cleavage of the test substance is likely between the phenoxyphenyl and phenylamino moieties, with greater amounts of tissue residues being associated with the phenylamino portion of the molecule. The focus of this rat metabolism and pharmacokinetic study will be on the phenylamino portion of the molecule.
Most of the administered dose is excreted as unchanged test substance in the feces.

Main ADME results

Main ADME results 1

Type:

absorption

Results:

Absorption half-life of [14C-PA]test substance increased from 0.8-1.2 hours to 3.5-7.1 hours as the dose level increased from 5 to 100 mg/kg. The absorption half-lives of [14C-POP]test substance at the 100 mg/kg appeared to be be rapid, at 0.4 to 1.4 hrs.

Main ADME results 2

Type:

distribution

Results:

At the 120-hour sampling interval, no specific retention of 14C-residues was observed in any of the examined tissues. Accumulation in the various organs and tissues were not observed, with the tissue/blood ratio <1.

Main ADME results 3

Type:

excretion

Results:

Greater than 90% of the administered radioactivity was recovered in the fecal excreta within 120 hours postdosing. Urinary elimination generally accounted for less than 10% of the administered dose.

Main ADME results 4

Type:

metabolism

Results:

Unmetabolized [14C]test substance was the major component recovered from the fecal excreta. Mono- (IN-KZ007) and dihydroxylated (IN-KZ534) test substance were identified as primary metabolites, recovered only from the feces.

Toxicokinetic / pharmacokinetic studies

Details on absorption:

The initial absorption of [14C-PA]test substance following oral dosing of 5 mg/kg was rapid. The apparent absorption half-lives of total [14C]-residues in the whole blood and plasma were approximately 0.8 to 1.2 hours.
The absorption half-life of [14C-PA]test substance increased from 0.8-1.2 hours to 3.5-7.1 hours as the dose level increased from 5 to 100 mg/kg. However, the absorption half-lives of [14C-POP]test substance at the 100 mg/kg high dose level appeared to be rapid, at approximately 0.4 to 1.4 hours. This observation suggested the potential absorption of the metabolite(s) derived from the phenylamino moiety.

Details on distribution in tissues:

Liver and body fat appeared to be the two primary tissues for the distribution of [14C-PA]test substance equivalent residues during the initial phase after oral exposure (at tcmax).
Tissue residues were eliminated rapidly. At the t cmax/2sampling interval, liver was the only tissue containing significant [14C-PA]test substance equivalent residues, where tissue/blood ratio was >1.0. At the 120-hour sampling interval, no specific retention of 14C-residues was observed in any of the examined tissues.

Details on excretion:

Greater than 90% of the administered radioactivity was recovered in the fecal excreta within 120 hours postdosing. Urinary elimination generally accounted for less than 10% of the administered dose. Elimination was rapid; the majority of the administered dose was eliminated usually within the initial 24 hours. 14CO2 was not detected in the expired air.

Toxicokinetic parameters

Test no.:

#1

Toxicokinetic parameters:

other: Absorption half life

Remarks:

[14C-PA]test substance: ~0.8-1.2 hours (5 mg/kg); ~3.5-7.1 hours (100 mg/kg) [14C-POP]test substance: ~0.4-1.4 hours (100 mg/kg);

Metabolite characterisation studies

Metabolites identified:

yes

Details on metabolites:

Unmetabolized [14C]test substance was the major component recovered from the fecal excreta. Mono- (IN-KZ007) and dihydroxylated (IN-KZ534) test substance were identified as primary metabolites, recovered only from the feces. Cleavage products, including IN-KZ000 sulfate and 4-acetoxyanxline were the primary urinary metabolites recovered from the [14C-POP] and [14C-PA] test substance treated animals, respectively.

Applicant's summary and conclusion

Conclusions:

Greater than 90% of the administered radioactivity was recovered in the fecal excreta within 120 hours postdosing. Urinary elimination generally accounted for less than 10% of the administered dose. Elimination was rapid; the majority of the administered dose was eliminated usually within the initial 24 hours. 14CO2 was not detected in the expired air.
Unmetabolized [14C]test substance was the major component recovered from the fecal excreta. Mono- (IN-KZ007) and dihydroxylated (IN-KZ534) test substance were identified as primary metabolites, recovered only from the feces.
Cleavage products, including IN-KZ000 sulfate and 4-acetoxyanxline were the primary urinary metabolites recovered from the [14C-POP] and [14C-PA] test substance treated animals, respectively.
Accumulation of [14C-PA] or [14C-POP] test substance equivalent residues in the various organs and tissues were not observed, with the tissue/blood ratio <1.
No significant differences in the overall metabolic fate of the test substance in the male vs the female test animals, high vs low dose, single vs multiple dosing regimen were observed.

Executive summary:

The absorption, distribution, metabolism and elimination of the test substance was examined according to the guideline EPA 85-1. These metabolic parameters were examined using [14C-Phenoxyphenyl (POP)] and [14C-Phenylamino (PA)] test substance in male and female Sprague-Dawley rats following a single or multiple oral dosing at the 5 or 100 mg/kg dose level. Greater than 90% of the administered radioactivity was recovered in the fecal excreta within 120 hours postdosing. Urinary elimination generally accounted for less than 10% of the administered dose. Elimination was rapid; the majority of the administered dose was eliminated usually within the initial 24 hours. 14CO2 was not detected in the expired air.

Unmetabolized [14C]test substance was the major component recovered from the fecal excreta. Mono- (IN-KZ007) and dihydroxylated (IN-KZ534) test substance were identified as primary metabolites, recovered only from the feces. Cleavage products, including IN-KZ000 sulfate and 4-acetoxyanxline were the primary urinary metabolites recovered from the [14C-POP] and [14C-PA] test substance treated animals, respectively.

Accumulation of [14C-PA] or [14C-POP] test substance equivalent residues in the various organs and tissues were not observed, with the tissue/blood ratio <1. Whole blood and plasma pharmacokinetic parameters were calculated to provide a description of the behavior and metabolic fate of the test substance in the test animals. Blood residue data showed the potential of binding of [14C-PA]test substance equivalent residues to the red blood cells.

No significant differences in the overall metabolic fate of the test substance in the male vs the female test animals, high vs low dose, single vs multiple dosing regimen were observed.