Pentapotassium ({[(hydroxyphosphinato)methyl](phosphonatomethyl)nitroryl}methyl)phosphonate

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

12.11.1991 to 16.07.1993

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1995

Report date:

1995

Materials and methods

Objective of study:

toxicokinetics

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 417 (Toxicokinetics)

Deviations:

yes

Remarks:

Only one dose tested.

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Nitrilotrimethylenetris(phosphonic acid)

EC Number:

229-146-5

EC Name:

Nitrilotrimethylenetris(phosphonic acid)

Cas Number:

6419-19-8

Molecular formula:

C3H12NO9P3

IUPAC Name:

[nitrilotris(methylene)]tris(phosphonic acid)

Test material form:

solid

Radiolabelling:

yes

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Portage or Charles River Kingston
- Age at study initiation: 51 to 81 days
- Weight at study initiation: 242 to 393 grams
- Fasting period before study: No data
- Housing: Individual stainless steel cages with wire mesh bottoms, or Roth-type metabolism cages.
- Individual metabolism cages: yes
- Diet: Ad libitum
- Water: Ad libitum
- Acclimation period: 14-31 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): No data
- Humidity (%): No data
- Air changes (per hr): No data
- Photoperiod (hrs dark / hrs light): 12 hours dark / 12 hours light


IN-LIFE DATES: From: 27.12.1991 To: 16.07.1993

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: Test substance was dissolved in distilled water. All dosing solutions were aliquoted by weight, diluted and weighed portions were counted by Liquid Scintillation Counting to determine concentration and specific activity.


VEHICLE : Distilled water
- Justification for use and choice of vehicle (if other than water): N/A
- Concentration in vehicle: No data
- Amount of vehicle: 1 to 2 ml
- Lot/batch no.: No data
- Purity: No data


HOMOGENEITY AND STABILITY OF TEST MATERIAL: No data

Duration and frequency of treatment / exposure:

Single dose (animals killed ten days later)

Doses / concentrations

Dose / conc.:

150 mg/kg bw/day

Remarks:

Received dose was calculated by weighing syringe plus dosing needle before and after use. Specific activity of dosing solution = 1073600 dpm/mg; equivalent amount of radioactivity = 28.76 uCi/rat.

No. of animals per sex per dose / concentration:

Males: four
A further two rats (dosed as above) were sacrificed 1 day and 10 day post-treatment for whole-body autoradiography. 
A further two rats were dosed as above and were sacrificed after 72 hours. This group was used to determine whether radioactivity was present in expired CO2, but was not discussed in the study report.

Control animals:

no

Positive control reference chemical:

None

Details on study design:

- Dose selection rationale: No data
- Rationale for animal assignment (if not random): No data

Details on dosing and sampling:

PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled (delete / add / specify): urine, faeces, blood, tissues, cage washes
- Time and frequency of sampling: Urine, faeces and cage washes at 24 hour intervals after dosing until sacrifice, in-life blood samples were collected at 15 and 30 minutes, 1, 2, 4, 6, 12 and 24 hours after dosing, then daily thereafter. At sacrifice blood samples were obtained and the following tissues and organs obtained: liver, kidneys, bone (femur), spleen, skeletal muscle, bone marrow. Gastrointestinal contents were collected by flushing the intestinal tract with saline. All samples were stored frozen at -20oC.


METABOLITE CHARACTERISATION STUDIES
- Tissues and body fluids sampled: urine
- Time and frequency of sampling: 24 hours after treatment.
- From how many animals: Unclear from study report
- Method type(s) for identification: HPLC
- Limits of detection and quantification: No data

Statistics:

Data were presented as the mean ± the standard error of the mean (SEM).

Results and discussion

Toxicokinetic / pharmacokinetic studies

Details on absorption:

The percent of ATMP absorbed was calculated to be approximately 2.2 %.
Urine = 1.1% Cage wash = 0.305% Carcass = 0.209% Tissue/organs = 0.055% Gut contents = 0.022% Blood = 0.0006% Plasma = 0.0005%

Details on distribution in tissues:

Approximately 0.2 % of the dose was found in the carcass of animals dosed orally. Very little ATMP-derived radioactivity remained in any of the other analysed tissues ten days after dosing. When comparing the tissue to blood levels (see Table 2), the bones had the highest tissue to blood ratios.

Transfer into organs

Observation:

not determined

Details on excretion:

The major route of elimination was by faeces (84%), while urine (1.1%) contributed much less (see Table 1). No significant amount of 14C was present in exhaled carbon dioxide (no further details). 

Toxicokinetic parameters

Toxicokinetic parameters 1

Test no.:

#1

Toxicokinetic parameters:

half-life 1st: 5 hours (urinary)

Toxicokinetic parameters 2

Test no.:

#1

Toxicokinetic parameters:

half-life 2nd: 70 hours (urinary)

Toxicokinetic parameters 3

Test no.:

#1

Toxicokinetic parameters:

half-life 1st: 5.3 hours (whole body)

Toxicokinetic parameters 4

Test no.:

#1

Toxicokinetic parameters:

half-life 2nd: 299 hours (whole body)

Metabolite characterisation studies

Metabolites identified:

yes

Details on metabolites:

URINARY METABOLITES (24 hours sample) Parent compound = 25.1%, N-methyl derivative = 45.9%; Unidentified = 28.6% (no further details)

Any other information on results incl. tables

Table 1 Summary of urinary and faecal elimination.

Day	Faecal elimination (%)	Urinary elimination (%)
1	84.32	1.016
2	9.448	0.056
3	0.34	0.019
4	0.031	0.013
5 -10	0.242	0.0342

Table 2 Summary of blood:tissue ratios at Day 10

Tissue	Ratio
Tibia	191
Femur	158
Bone marrow	104
Sternum	75.6
Carcass	7.81
Gut contents	3.63
Kidneys	2.61
Spleen	1.8
Liver	1.1
Blood	1.0
Erythrocytes	0.792
Muscle	0.644
Plasma	0.02

RECOVERY DATA
Individual total recovery = 81.85 - 88.55%
Mean total recovery = 85.90% (SEM = 1.62)

AUTORADIOGRAPHY
At 24 h, the major regions of localisation of 14C were:
- gut contents
- stomach contents
- nasal turbinates
- bone and bone marrow
Radioactivity also observed in the kidney (no other tissues) and throughout all bones of the body (most intense in epiphyseal plate of the long bones and in nasal turbinates).

At 10 d post-dose, intense localisation still apparent in bone, especially the epiphyseal plate of the long bones. Some low level deposition of 14C was present in stomach lining and the kidneys (no other tissues affected). (The authors note that this pattern is consistent with that reported for EHDP.)

Applicant's summary and conclusion

Conclusions:

In a well conducted toxicokinetics study, conducted according to OECD TG 417 and in compliance with GLP, ATMP was poorly absorbed and rapidly eliminated after oral administration. Total recovery was 86%. The majority of the dose (84.2%) was excreted in the faeces and only 1.1% was excreted in the urine. The amount of radioactivity in the urine was used to determine the extent of absorption by comparing urinary excretion between orally and intravenously dosed rats. Using this approach, absorption following administration of 14C-labelled ATMP was shown to be approximately 2.2%. The initial and terminal urinary half-lives were approximately 5 and 70 hours, respectively. The initial phase whole-body elimination half-life was 5.3 hours and the terminal half-life was 299 hours. HPLC analysis of urine samples collected 24 hours after administration revealed the presence of the parent compound, the n-methyl derivative and an unidentified metabolite. Approximately 0.06% of the dose was found in the bone (femur, tibia and sternum) and 0.21% of the dose was found in the carcass. The overall tissue distribution confirmed that the highest levels of radioactivity were in the bone. The only tissue that demonstrated significant accumulation of ATMP-derived radioactivity was bone.