1-nitroguanidine

Endpoint summary

Link to relevant study record(s)

Reference

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1988

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Objective of study:

distribution

metabolism

toxicokinetics

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 417 (Toxicokinetics)

GLP compliance:

not specified

Radiolabelling:

yes

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Bantin-Kingman (Fremont, CA)
- Weight at study initiation: 150-200g
- Housing: individually in metabolism cages (Nalgene) - AALAS-accredited facilities
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 14 days
- Other: Animals were fasted prior to dosing

Route of administration:

other: intravenous and orally by intubation

Vehicle:

other: physiol. saline or DMSO + 1 % gum tragacanth

Details on exposure:

tissue distribution & blood kinetics:
group1: 20 mg/kg intravenously via tail vein with 5-10 µCi of radiolabel NiGu in 0,9% NaCl
group2: 20 mg/kg gavage with 7-11 µCi of radiolabel NiGu dissolved in DMSO & suspended in 1% gum tragacanth
group3: 200 mg/kg gavage with 5-10 µCi of radiolabel NiGu dissolved in DMSO & suspended in 1% gum tragacanth

Duration and frequency of treatment / exposure:

one-time treatment /exposure

Dose / conc.:

20 mg/kg bw/day

Remarks:

i.v.

Dose / conc.:

20 mg/kg bw/day

Remarks:

gavage

Dose / conc.:

200 mg/kg bw/day

Remarks:

gavage

No. of animals per sex per dose / concentration:

group 1: 6 male, 6 female
group 2: 6 male, 6 female
group 3: 6 male, 6 female

Control animals:

no

Details on dosing and sampling:

PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: urine, feces, blood, tissues, expired CO2

- Time and frequency of sampling:
- blood (gavage): 10, 20, 30, 40, 50, 60, 75, 90, 120 min; 3, 4, 6, 8, 12, 24 h;
- blood (i.v.): 5, 15, 30, 45, 60, 75, 90, 120 min; 3, 4, 5, 6, 7, 8, 24 h;
- urine samples: 4, 8, 24, 32, and 48 hr
- fecal samples: 24 and 48 hr

Sampling:
urin: 25 - 1000 µl aliquots; liquid scintillation counting (Packard Tri-Carb 4530 or 460-CD or 3390AAA)
feces: lyophilized and crushed; aliquots combusted prior to liquid scintillation counting
CO2: collected by bulbing through absorption towers; aliquots of absorbant were measured by liquid scintillation counting

Statistics:

Two-way analysis of variance was performed to test for differences in excretion and distribution of radiolabel by the various dose groups at the indicated time points. The Newman-Keuls method of multiple comparisons was then performed to compare excretion of radiolabel by dose group and/or sex. All tests were done at p=0.05 level of significance. Data from blood kinetics experiments were analyzed by non-linear regression analysis to give values for t1/2alpha/2beta, AUC, VDss, tmax, and Cmax.

Preliminary studies:

data not shown: no radiolabel present in the expired air

Details on absorption:

The absorption of orally dosed (group B) versus i.v. dosed (group A) is 100 %; the route of administration does not appear to influence the absorption of radiolabel.

Details on distribution in tissues:

The tissue distribution of [14C]-nitroguanidine is shown in Table 2. After 48 h there was no significant radioactivity (0,02 %) remaining in any organ.
The distribution 1 hour after administration of 20 mg/kg (oral) is shown in Table 3 in the field "Overall remarks and attachments". A large amount of radiolabel is found in the GI tract (5.3 %), as expected with an oral dose, followed by kidney (1.3 %) and liver (1 %).

Details on excretion:

The administered radioactivity was rapidly excreted in the urine by animals in all dose groups. 40-50% was excreted after 4 h postdose. Approx. 95% of administerd radiolabel was recovered in the urine after 48h; low amount of radiolabel were detected in the feces (likely to be inflated due to urine contamination of feces in the metabolic cages);
The cumulative recovery of radioactivity in the urine is shown in table 1 in the field Overall remarks and attachments.
The distribution and excretion of radioactivity 48 hours after administration of [14C] nitroguanidine is shown in table 2.

Key result

Test no.:

#1

Toxicokinetic parameters:

half-life 1st: t1/2 α-phase (h): group 1: 0.08 +- 0.01; group 2: 0.21 +- 0.24; group 3: 0.82 +- 0.67

Key result

Test no.:

#2

Toxicokinetic parameters:

half-life 2nd: t1/2 β-phase (h): group 1: 1.78 +- 0.14; group 2: 2.60 +- 0.10; group 3: 2.94 +- 1.07

Key result

Test no.:

#3

Toxicokinetic parameters:

AUC: AUC (µg/ml/hr): group 1: 79.98 +- 10.05; group 2: 92.64 +- 26.80; group 3: 969.07 +- 149.92

Key result

Test no.:

#4

Toxicokinetic parameters:

other: VDss(1/kg): group 1: 0.66 +- 0.12; group 2: 0.87 +- 0.20; group 3: 0.85 +- 0.19

Key result

Test no.:

#5

Toxicokinetic parameters:

Tmax: t max(h): group 1: not applicable; group 2: 0.69 +- 0.62; group 3: 1.77 +- 0.86

Key result

Test no.:

#6

Toxicokinetic parameters:

Cmax: Cmax(µg/ml): group 1: not applicable; group 2: 19.93 +- 2.01; group 3: 149.44 +- 22.96

Metabolites identified:

no

Details on metabolites:

Substance is not metabolized and is excreted unchanged as nitroguanidine. Under aerobic conditions nitroguanidine does not undergo metabolism in the rat.
Previous studies showed that :
- Nitroguanidine is reduced to nitrosoguanidine by anaerobic sludge microorganisms.

Results from the reverse-phase HPLC analysis of a representative urine sample indicate the presence of one major radioactive component in the urine, which has an elution volume of 3.7 ml. This elution volume corresponds exactly (99%) to that of nitroguanidine standard as evidenced by uv detection.

Conclusions:

There was no significant radioactivity remaining in any of the major organs of the treated animals. No sex differences in groups were seen in the excretion of the radiolabel after 48 hours. The route of administration does not appear to influence the absorption of radiolabel. No dose dependency of absorption between oral doses of 20 and 200 mg/kg is indicated.
Nitroguanidine is rapidly and completely absorbed in all dose groups. Nitroguanidine is well distributed to the tissues of all animals regardless of the route of administration. Nitroguanidine is rapidly distributed in the blood to the major organs.

Executive summary:

Results from initial experiments showed no radiolabel to be present in the expired air of animals treated with [14C]nitroguanidine. Approximately 95 % of the administered radiolabel was recovered in the urine of the animals in all dose groups after 48 hours. The amount of radioactivity in the feces was low and it is likely that these values are inflated due to urine contamination of the feces in the metabolic cages. At 48 hours after dosing, the animals were removed for analysis. There was no significant radioactivity remaining in any of the major organs of the treated animals.

 

The administered radioactivity was rapidly excreted in the urine by animals in all dose groups. Between 40 and 50 % of the radiolabel had been excreted in the urine 4 hours postdose and nearly all the administrated radiolabel was found in the urine after 24 hours.

No sex differences in groups were seen in the excretion of the radiolabel after 48 hours.

The absorption of radiolabel by orally dosed group B versus i.v. dosed group A is 100 %; the route of administration does not appear to influence the absorption of radiolabel.

The GI tract absorption of radiolabel by animals in group 2 and group 3 is essentially complete, indicating no dose dependency of absorption between oral doses of 20 and 200 mg/kg.

The results indicate that nitroguanidine is well distributed to the tissues of all animals regardless of the route of administration or dose regiment and that nitroguanidine is rapidly distributed in the blood to the major organs.

Description of key information

Short description of key information on bioaccumulation potential result:
A toxicokinetic study in rat according OECD 417 was conducted to assess absorption,

distribution, elimination and metabolism of Nitroguanidine.

Nitroguanidine is rapidly distributed and rapidly excreted. 40 - 50 % of the substance is excreted in the urine 4 hours postdose

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

Based on an OECD 417 Guideline study in rats Nitroguanidin is considered to be well absorbed regardless of the route of administration or dose regime. Nitroguanidine is rapidly distributed and rapidly excreted. 40 - 50 % of the substance is excreted in the urine 4 hours postdose and nearly all the administered radiolabel was found in the urine after 24 hours. No metabolites were identified.

Discussion on bioaccumulation potential result:

Nitroguanidine is rapidly and completely absorbed in all dose groups. The bioavailability of NG in orally dosed groups is 100% as compared to the i.v. dosed group when calculated using either urinary or blood level data. Initial experiments showed no radiolabel to be present in the expired air. Nitroguanidine is well distributed to the tissues of all animals regardless of the sex, route of administration or dose regime. Nitroguanidine is rapidly excreted in the urine by animals in all dose groups. Between 40 and 50 % of the radiolabel is excreted in the urine 4 hours postdose and nearly all the administrated radiolabel was found in the urine after 24 hours. After 48 h the excretion is considered quantitative. Nitroguanidine is not metabolized but excreted solely in its unchanged form.