Methenamine

Toxicity to reproduction

Administrative data

Endpoint:

three-generation reproductive toxicity

Remarks:

based on test type

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1970

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: old public available literature (no GLP, non guideline)

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

publication

Title:

Studio della tossicita transplacentare edi cancerogenesi in ratti trattati con esametilentetramina

Author:

Della Porta, G.; Cabral, J. R.; Parminani, G.

Year:

1970

Bibliographic source:

Tumori, 56: 325-334, 1970

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Public available literature. No guideline indicated. For details on method see IUCLID5 materials and methods section.

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Methenamine

EC Number:

202-905-8

EC Name:

Methenamine

Cas Number:

100-97-0

Molecular formula:

C6H12N4

IUPAC Name:

1,3,5,7-tetraazatricyclo[3.3.1.1³,⁷]decane

Details on test material:

not indicated.

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

- 3-4 rats per cage
- diet and water ad libitum

Administration / exposure

Route of administration:

oral: drinking water

Vehicle:

water

Details on exposure:

Rats were given 1% methenamine in drinking water for three successive generations, up to the age of 40 weeks in the F1 and F2 groups and of 20 weeks for the F3 group, thereafter all groups were kept under observation up to week 130 of their lifetime.
An additional test group of 5 females was run on 2% methenamine from mating through lactation.

Details on mating procedure:

F0: 1 male was mated with 2 females (no further details given).
F1: 3 males were mated with 7 females
F2: 4 males were mated with 11 females

Analytical verification of doses or concentrations:

not specified

Details on analytical verification of doses or concentrations:

no details on analytical verification of doses.

Duration of treatment / exposure:

F0: 4 weeks before mating, 25-30 days of pregnancy (no further details given on F0 generation)
F1: total treatment 40 weeks, mating in week 26
F2: total treatment 40 weeks, mating in week 15
F3: total treatment 20 weeks

Frequency of treatment:

continuous via the drinking water.

Details on study schedule:

Rats were given 1% methenamine in drinking water for three successive generations, up to the age of 40 weeks in the F1 and F2 groups and of 20 weeks for the F3 group, thereafter all groups were kept under observation up to week 130 of their lifetime. The parental generation (F0) group consisted of one male and two females that were given 1% methenamine in drinking water during four weeks before mating. The treatment of the females continued until two litters of ten pups each had been weaned. The descendant F1 groups consisted of 13 males and 7 females. The females were mated to 3 males of their group. One dam died during delivery while the remaining 6 dams gave birth to a total of 36 pups from which 10 died during lactation. The resulting F2 group consisted of 15 males and of 11 females. These females were mated to 4 males of their group and delivered a total of 99 pups from which only 12 males and 12 females were further raised to yield the F3 group.
An additional test group of 5 females was run on 2% methenamine from mating through lactation. They delivered a total of 49 pups from which 16 animals per sex were continued on 2% methenamine for 50 weeks. All groups were kept under observation for over two years of age.

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0, 1 % (daily intake of approximately 1.5-2 g/kg bw/d for males and of 2-2.5 g/kg bw/d for females)
Basis:
nominal in water
3 generation study

Doses / concentrations 2

Remarks:

Doses / Concentrations:
0, 2 % (daily intake of approximately 3.0-4.0 g/kg bw/d for males and of 4.0-5.0 g/kg bw/d for females)
Basis:
nominal in water
additional one generation study

No. of animals per sex per dose:

F0: 2 females and 1 males
F1: 7 females, 13 males
F2: 11 females, 15 males
F3: 99 pups in total, 12 of each sex were selected for treatment for an other 20 weeks

Control animals:

yes, plain diet

Details on study design:

no further details given.

Positive control:

no positive control.

Examinations

Parental animals: Observations and examinations:

- water intake
no further details on F0 animals observations given.
F1, F2 and F3 animals: mortality, body weights, clinical symptoms

Oestrous cyclicity (parental animals):

not examined.

Sperm parameters (parental animals):

not examined.

Litter observations:

- number and sex of litters
- body weigh and body weight gain

Postmortem examinations (parental animals):

not details given.

Postmortem examinations (offspring):

- pathology (macroscopic and microscopic) of organs (carcinogenicity)

Statistics:

Student's t-test

Reproductive indices:

not calculated/examined.

Offspring viability indices:

not calculated/examined.

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:

no effects observed

Body weight and weight changes:

not specified

Food consumption and compound intake (if feeding study):

not specified

Organ weight findings including organ / body weight ratios:

not examined

Histopathological findings: non-neoplastic:

not examined

Other effects:

no effects observed

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

not examined

Reproductive performance:

no effects observed

Details on results (P0)

Only very limited data for parental animals were available.

Effect levels (P0)

Key result

Dose descriptor:

NOAEL

Effect level:

>= 1 500 - <= 2 500 mg/kg bw/day (nominal)

Sex:

male/female

Basis for effect level:

other: no adverse effects on parental animals were reported.

Target system / organ toxicity (P0)

Key result

Critical effects observed:

no

Results: F1 generation

General toxicity (F1)

Clinical signs:

no effects observed

Mortality / viability:

mortality observed, treatment-related

Body weight and weight changes:

no effects observed

Sexual maturation:

no effects observed

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings:

no effects observed

Details on results (F1)

The survival rates of all raised offspring generations (except F2) were not affected by any treatment and the body weights did not show significant differences between control and treated groups. Postnatal mortality was observed in the weanlings (F2 generation) of the methenamine exposed groups. Reproductive capacity and capability was not obviously affected during this study.
Anymore detailed information on reproductive endpoints is not available from this study since it had been primarily directed to elucidate carcinogenicity.

Results: F2 generation

Effect levels (F2)

Key result

Dose descriptor:

LOAEL

Generation:

F2

Effect level:

>= 1 500 - <= 2 500 mg/kg bw/day (nominal)

Sex:

male/female

Basis for effect level:

other: Postnatal mortality was observed in the weanlings (F2 generation) of the methenamine exposed groups.

Overall reproductive toxicity

Reproductive effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

Postnatal mortality was observed in the weanlings (F2 generation) of the methenamine exposed groups. Reproductive capacity and capability was not affected during this study. Thus, the dosage of 1.5-2.5 g /kg bw/day may represent a LOAEL for developmental toxicity. The doses used exceed the recommended maximum doses in respective OECD/EU guidelines.

Executive summary:

In a further study on transplacental toxicity and carcinogenesis with Wistar rats, the outcome of the exposure of animals to methenamine via drinking water was followed up in two independent experiments for one and for three successive generations. The results of the first experiment are presented in a separate endpoint study record.

In a second experiment rats were given 1% methenamine in drinking water for three successive generations, up to the age of 40 weeks in the F1 and F2 groups and of 20 weeks for the F3 group, thereafter all groups were kept under observation up to week 130 of their lifetime. The parental generation (F0) group consisted of one male and two females that were given 1% methenamine in drinking water during four weeks before mating. The treatment of the females continued until two litters of ten pups each had been weaned. The descendant F1 groups consisted of 13 males and 7 females. The females were mated to 3 males of their group. One dam died during delivery while the remaining 6 dams gave birth to a total of 36 pups from which 10 died during lactation. The resulting F2 group consisted of 15 males and of 11 females. These females were mated to 4 males of their group and delivered a total of 99 pups from which only 12 males and 12 females were further raised to yield the F3 group. An additional test group of 5 females was run on 2% methenamine from mating through lactation. They delivered a total of 49 pups from which 16 animals per sex were continued on 2% methenamine for 50 weeks. All groups were kept under observation for over two years of age. The survival rates of all raised offspring generations (except F2 generation) were not affected by any treatment and the body weights did not show significant differences between control and treated groups. Anymore detailed information on reproductive endpoints is not available from this study since it had been primarily directed to elucidate carcinogenicity. The doses used exceed the recommended maximum doses in respective OECD/EU guidelines.