Metformin hydrochloride

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / bone marrow chromosome aberration

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1991

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1992

Report date:

1992

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

Deviations:

no

GLP compliance:

yes

Type of assay:

other: Mouse MN test OECD 474

Test material

Test material information

Constituent 1

Reference substance name:

Metformin hydrochloride

EC Number:

214-230-6

EC Name:

Metformin hydrochloride

Cas Number:

1115-70-4

Molecular formula:

C4H11N5.ClH

IUPAC Name:

N,N-dimethylimidodicarbonimidic diamide hydrochloride

Test material form:

solid: bulk

Test animals

Species:

mouse

Strain:

CD-1

Details on species / strain selection:

Strain: SPF outbred CD1
Source: Charles River UK
Weight: 22-24 g
Age: 35 d

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River UK
- Age at study initiation: 35 d
- Weight at study initiation: 22-24 g
- Assigned to test groups randomly: yes, under following basis: separated by sex
- Fasting period before study: overnight prior to and for 2 hours after dosing
- Housing: grouped separated by sex plastic cages
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum) ad libitum:
- Acclimation period: 4 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 °C
- Humidity (%): n.d.
- Air changes (per hr): 30
- Photoperiod (hrs dark / hrs light): 12/12 h

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

Water

Duration of treatment / exposure:

single dose

Frequency of treatment:

1

Post exposure period:

24, 48, 72 h after dosing

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

2 000 mg/kg bw/day

Doses / concentrations 2

Dose / conc.:

0 mg/kg bw/day

No. of animals per sex per dose:

Neg. Control: 15 f, 15 m
2000 mg/kg Metformin HCl: 20 f, 20 m
Pos. Control: 5 f, 5 m

Control animals:

yes

Positive control(s):

12 mg/kg bw Mitomycin C

Examinations

Tissues and cell types examined:

Bone marrow

Details of tissue and slide preparation:

- direct bone marrow smears prepared on slides
- Methanol fixation (10 min)
- Giemsa staining

Evaluation criteria:

MN incidence per 1000 PCEs per animal

Statistics:

Standard statistical methods have been applied for data processing.

Results and discussion

Test results

Key result

Sex:

male/female

Genotoxicity:

negative

Toxicity:

yes

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Any other information on results incl. tables

Summary of results - group totals/means for the entire experiment and results of the statistical analysis

Samplng Time	Treatment	Dose / (mg/kg)	Ratio p/n (mean) §	Incidence mnp (mean) §	Incidence mnn (total)
24 hour	Vehicle control	-	0.847	0.2	0.2
	Metformin HCl	2000	1.059^ns	0.9^ns	0.2
	Mitomycin C	12	0.759^ns	40.3 ***	0.4
48 hour	Vehicle control	-	1.146	1.0	0.2
	Metformin HCl	2000	0.936^ns	0.6^ns	0.4
72 hour	Vehicle control	-	1.228	0.8	0.6
	Metformin HCl	2000	1.165^ns	0.2^ns	0.4

p/n   Ratio of polychromatic to normocbromatic erythrocytes
mnp   Number of micronucleaied cells observed per 1000 polycbromatic erythrocytes
mnn   Number of micronucleated cells observed per 1000 normochromatic erythrocytes

§ Results of statistical analysis using Wilcoxon's sum of ranks test (one-sided):

    ns       P > 0.05
    ***    P < 0.001

Applicant's summary and conclusion

Conclusions:

It is concluded that Metformin hydrochloride has not shown any evidence of causing chromosome damage in this in vivo test.

Executive summary:

This study was performed according to GLP and the methods applied are fully compliant with OECD TG 474. It is concluded that Metformin hydrochloride has not shown any evidence of causing chromosome damage in this in vivo test.