Metformin hydrochloride

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1994

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: FDA TAD 4.08

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations:
Nominal Test Concentrations: Control, 10, 20, 40, 80 and 160 mg/L
Mean Measured Concentrations: 0.00, 9.7, 19, 39, 78 and 160 mg/L
- Sampling method: Analytical samples were taken at 0, 24, and 48-hours
- Sample storage conditions before analysis: 4°C

Vehicle:

no

Test organisms (species):

Daphnia magna

Details on test organisms:

Source: in-house daphnid culture from ABC
Primary culture source: Columbia National Fisheries Research Laboratory (CNFRL), Columbia, Missouri

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

134 to 252 mg/L CaCO3

Test temperature:

21°C

pH:

8.2 to 8.5

Dissolved oxygen:

7.6 to 8.1 mg/L

Nominal and measured concentrations:

nominal: 10, 20, 40, 80, and 160 mg/L
analytical: 9.7, 19, 39, 78, and 160 mg/L

Details on test conditions:

TEST SYSTEM
- Type (delete if not applicable): all test vessels were covered with loose-fitting petri dish covers to minimize evaporation
- Material, size, headspace, fill volume: 250 mL glass beakers containing a 210 test volume
- Aeration: No
- Renewal rate of test solution (frequency/flow rate): no renewal, static system
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4

TEST MEDIUM / WATER PARAMETERS
Source/preparation of dilution water: Hard Blended Water:

Hardness: 152 mg/L (as CaCO3)
Alkalinity: 164 mg/L (as CaCO3)
pH: 8.4
Temperature: 25.4°C
Dissolved Oxygen: 7.9 mg/L
Conductivity: 320 µmbos/cm

- Culture medium different from test medium: No
- Intervals of water quality measurement: daily

OTHER TEST CONDITIONS
- Adjustment of pH: No
- Photoperiod: 16h light : 8h dark

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Immobilization

VEHICLE CONTROL PERFORMED: no

RANGE-FINDING STUDY:

A range-finding experiment was conducted with Metformin HC1 using five Daphnia magna in each of the exposure concentrations of control, 1.0, 10, 100, and 1000 mg/L. No immobility or abnormal effects were observed in the control, 1.0, and 10 mg/L test concentrations after 24 and 48 hours. The 100 mg/L test solution showed 40% immobilization after 24 hours and 80% immobilization after 48 hours. The 1000 mg/L test solution showed 100% immobilization after 24 hours.

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

130 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 95% confidence limits: 78 - 160 mg/L

Key result

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

78 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

- Behavioural abnormalities: No
- Observations on body length and weight: No
- Other biological observations: No
- Mortality of control: No
- Other adverse effects control: No
- Immobilisation of control: No
- Abnormal responses: No
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: No
- Effect concentrations exceeding solubility of substance in test medium: No

Results with reference substance (positive control):

The following reference toxicant tests with Daphnia magna have been conducted by ABC Laboratories within a year of the acute study with Metformin HCl. The reference toxicant test were conducted using potassium chloride supplied by Sigma Chemical Company. The potassium chloride tests were conducted from August 25, 1993 through August 27, 1993, December 7, 1993 through December 9, 1993, February 23, 1994 through February 25, 1994, and June 8, 1994 through June 10, 1994. The 48-hour LC50 values were 707, 707, 676, and 707 mg/L, respectively. The expected 48-hour LC50 range was 700-1100 mg/L (3). From February 23, 1994 through February 25, 1994, and June 8, 1994 through June 10, 1994 reference toxicity tests were conducted with cadmium chloride. The 48-hour LC50 values were 0.024 and 0.12 mg/L for the cadmium chloride tests, respectively. The expected 48-hour LC50 range for cadmium chloride was 0.010-0.090 mg/L. The cadmium chloride was supplied by the U.S. EPA Environmental Monitoring and Support Laboratory, Cincinnati, Ohio. All data are on file at ABC Laboratories.

For details see executive summary

Validity criteria fulfilled:

yes

Conclusions:

The 24- and 48-hour estimated EC50, values for Daphnia magna exposed to metformin HCl were > 160 mg/L and 130 mg/L, respectively. A NOEC of 78 mg/L was determined.

Executive summary:

Study Design

The acute toxicity of Metformin HCl to Daphnia magna was assessed in a GLP study using the methods patterned after the FDA Technical Assistance Document 4.08.
Water quality parameters of temperature, dissolved oxygen, pH, hardness, and alkalinity were measured throughout the test and were within acceptable limits. The daphnids used for this study were first-instar daphnids (< 24 hours old) and were cultured at ABC Laboratories. Culture records indicated the adult daphnids were in good condition.

The study was conducted at the nominal concentrations of 10, 20, 40, 80, and 160 mg/L of Metformin HCl in quadruplicate replicate. A fifth replicate for each level was prepared and was used to perform 0- and 24-hour water quality measurements. There were five daphnids per replicate for a total of 20 daphnids exposed to each concentration and the control. Hard blended water was used as the dilution water for this study. Water quality parameters of temperature, dissolved oxygen, pH, total hardness, and total alkalinity were measured at 0, 24, and 48 hours of the study.

Results

All water quality parameters were within acceptable limits with the exception of control replicate B which had been contaminated with water from the test system waterbath. The hardness measurement of replicate B of the control exceed the required range of 130-160 mg/L as CaCO₃.

Samples were collected at 0, 24, and 48 hours for analytical confirmation. The overall mean measured concentrations were 9.7, 19, 39, 78, and 160 mg/L of Metformin HCl.

The 24- and 48-hour estimated EC₅₀, values for Daphnia magna exposed to metformin HCl were > 160 mg/L and 130 mg/L, respectively. The 48-hour no-observed effect concentration was 78 mg/L, based on the lack of immobility and abnormal effects at this concentration.

Conclusion

The 24- and 48-hour estimated EC₅₀, values for Daphnia magna exposed to metformin HCl were > 160 mg/L and 130 mg/L , respectively. From the data obtained a NOEC of 78 mg/L metformin HCl was determined.

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1992

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study without detailed documentation

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

GLP compliance:

not specified

Specific details on test material used for the study:

no further details are being provided

Analytical monitoring:

no

Test organisms (species):

Daphnia magna

Details on test organisms:

see publication for details

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Post exposure observation period:

no

Hardness:

no data

Test temperature:

20 +/- 1 °C

pH:

no data

Dissolved oxygen:

no data

Salinity:

no data

Conductivity:

no data

Nominal and measured concentrations:

Generally, test substance applied in at least five concentrations (1, 3.2 10, 32, 100 mg/L). Depending on the results, some tests were repeated including lower (0.1 and 0.32 mg/L) or higher (320 mg/L) concentrations.

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

64 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Results with reference substance (positive control):

no data

Conclusions:

The EC50 obtained after 48 h exposure to the test material ammounts to 64 mg/L.

Description of key information

A 48h-EC50 of 64 mg/L was determined in a literature study following the European Guideline: ‘Methods for determination of ecotoxicity; Annex V, C2, Daphnia acute immobilisation test’ (Commission of the European Communities, 1992). However, no analysis of the test item concentration during the study was performed. Furthermore, no details regarding purity, batch, expiration etc. of the test item are available and, thus, this result is only used as supportive information.

A valid study under GLP conditions including the verification of the different test item concentrations was also performed. The 24- and 48-hour estimated EC50 values for Daphnia magna exposed to metformin HCl were > 160 mg/L and 130 mg/L, respectively. A NOEC of 78 mg/L was determined.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

130 mg/L