N-methylformamide

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Comparable to Guideline study with acceptable restrictions (treatment period gestation day 6-15; partly limited documentation, e.g. no details about the test substance; untreated control; no historical control data).

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1975

Report date:

1975

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

no

Principles of method if other than guideline:

according to Guidelines for reproduction studies for safety evaluation of drugs for human use. Food and Drug Administration, Washington 1966

GLP compliance:

no

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

monomethylformamide

IUPAC Name:

monomethylformamide

Details on test material:

technical product
no further details

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

Source: Wiga, Sulzfeld, Germany
Only females with vaginal plug used (gestation day 0 [GD0] )
Housing conditions:
2 animals per cage
temperature 20-24°C
rel. air humidity: 50-60%
dark/light cycle: 12/12 h
certified diet and tap water ad libitum

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

water

Details on exposure:

Constant application volume in all dose groups: 5 ml/kg bw
Dose related to the initial weight at GD0
Solutions prepared daily

Analytical verification of doses or concentrations:

not specified

Details on mating procedure:

Mating with fertile, untreated males for one night; only females with vaginal plug used (gestation day 0)

Duration of treatment / exposure:

Gestation day (GD) 6-15

Frequency of treatment:

once daily

Duration of test:

Termination at GD20, cesarean section

Doses / concentrations

Remarks:

Doses / Concentrations:
22, 67, 200 mg/kg bw/day
Basis:
actual ingested

No. of animals per sex per dose:

20-24 pregnant animals

Control animals:

yes, concurrent no treatment

Details on study design:

- Dose selection rationale: data from acute oral toxicity in rats
- Rationale for animal assignment: randomisation

Examinations

Maternal examinations:

Clinical symptoms recorded daily
Body weight measured thrice weekly

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: no data
- placenta weight of living fetuses
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- dead and living fetuses

Fetal examinations:

weight, length, sex of fetuses
all fetuses examined for external effects
2/3 of all fetuses processed for the study of skeletal effects (Dawsen-method; Alizarin staining)
1/3 of all fetuses processed for the study of visceral effects (fixation in Bouin's solution for 2 weeks, 15 transversal sections)

Statistics:

Analysis of variance
t-test
level of significance: p<0.05

Indices:

see results

Historical control data:

no data available

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
No clinical signs and no mortality in any treatment group except a vaginal bleeding in 6 dams of the high dose group (considered to be related to developmental toxicity, no further effects in the high dose group).
>=67 mg/kg bw/day: reduced body weight gain; considered to be related to resorption of implantations in the high dose group or reduced fetal weight at 67 mg/kg bw/day (developmental toxicity but not maternal toxicity; in the mid dose group the difference was less than 5% to the concurrent control).
No effects on body weight gain in the low dose group.

Effect levels (maternal animals)

1

Dose descriptor:

NOAEL

Effect level:

200 mg/kg bw/day

Basis for effect level:

other: maternal toxicity

2

Dose descriptor:

NOAEL

Effect level:

22 mg/kg bw/day

Basis for effect level:

other: developmental toxicity

3

Dose descriptor:

LOAEL

Effect level:

67 mg/kg bw/day

Basis for effect level:

other: developmental toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
No effects on number of implantations in any treatment group (varied between 11.10 and 11.96 implantations per dam)

200 mg/kg bw/day:
99.6% of implantations were resorbed, mainly early resoptions; only 1 fetus alive but with malformations (e.g. exencephaly & ectopia visceralis).

67 mg/kg bw/day:
no increase in dead implantations (resorptions and dead fetuses) and no effects on number of living fetuses
decrease in fetal body weight and length
decrease in placental weight
increase in variations (no details) and malformations (mainly meningocele, malformations of ribs and vertebral column; see also Table below)

22 mg/kg bw/day:
no developmental toxicity, placental weight slightly decreased although fetal weight increased (no data about historical controls; not considered by the authors to be of toxicological relevance).

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

Developmental toxicity in Sprague-Dawley rats after oral application of N-methylformamide

Parameter	Dose in mg/kg bw/day
	Control 1	22	Control 2	67	Control 3	200
Pregnant dams	23	24	20	21	24	23
Placenta weight g	0.54	0.52*	0.58	0.42**	0.59	0.32**
Dead implantations	6	9	7	12	11	265**
living fetusus per dam	11.70	11.17	10.75	10.86	11.50	0.04
Fetal weight in g	3.66	3.82**	3.66	3.21**	3.66	1 male, 2.41
Fetal length in cm	3.63	3.64	3.54	3.37**	3.60	3.2
Fetuses with malformations in % of fetuses examined	1.12%	0.37%	1.4%	51%$	0.36%	Only 1 fetus (malformed)

*: significant, p<0.05; **: p<0.01; $: no data about significance but clear teratogenic effect

Slight but significant decrease in placenta weight at 22 mg/kg bw

Applicant's summary and conclusion

Conclusions:

Developmental toxicity was found in rats at dose levels without maternal toxicity; the NOAEL was 22 mg/kg bw/day, LOAEL 67 mg/kg bw/day.

Executive summary:

Comparable to Guideline study with acceptable restrictions (treatment period gestation day 6-15; partly limited documentation, e.g. no details about the test substance; untreated control; no historical control data).

Groups of 20 -24 pregnant Sprague-Dawley rats were gavaged at gestation day (GD) 6 -15 with 22, 67, or 200 mg/kg bw/day. Concurrent controls were untreated. The study was terminated GD20. No maternal toxicity was observed in any treatment group. The reduced body weight gain in dams was considered to be related to resorption of implantations in the high dose group or the decrease in fetal weight at the mid dose level (developmental toxicity but not maternal toxicity). No effects were found on implantations, but only 1 male fetus was alive at termination in the high dose group and this one had malformations. At 67 mg/kg bw/day no increase in resorptions and dead fetuses was found, but a decrease in fetal body weight and length, and increase in variations (no details) and malformations (51% of examined fetuses with malformations) was reported. At 22 mg/kg bw/day no developmental toxicity was detected.

Conclusion: Developmental toxicity was found in rats at dose levels without maternal toxicity; the NOAEL was 22 mg/kg bw/day, LOAEL 67 mg/kg bw/day.