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Metronidazole
Last updated: 12/10/2023
(Also known as: metronidazol ; MTZ)
Data alerts

The following alerts are based on the data in the tables below. An absence of an alert does not imply the substance has no implications for human health, biodiversity or the environment but just that we do not have the data to form a judgement.

Environmental fate Ecotoxicity Human health
Environmental fate
High alert:
Drainflow: Mobile
Warning:
Significant data are missing
Ecotoxicity
Low alert:
Birds acute ecotoxicity: Low; Fish acute ecotoxicity: Low; Daphnia acute ecotoxicity: Low
Human health
High alert:
Neurotoxicant
GENERAL INFORMATION
Description
Used to treat infections caused mainly by Gram-positive and Gram-negative bacteria and protozoa
Availability status
Current
Introduction & key dates
1957, introduced
Examples of species treated
Cattle, Dogs, Cats, Horses, Donkeys
Chemical structure
Isomerism
-
Chemical formula
C₆H₉N₃O₃
Canonical SMILES
CC1=NC=C(N1CCO)[N+](=O)[O-]
Isomeric SMILES
No data
International Chemical Identifier key (InChIKey)
VAOCPAMSLUNLGC-UHFFFAOYSA-N
International Chemical Identifier (InChI)
InChI=1S/C6H9N3O3/c1-5-7-4-6(9(11)12)8(5)2-3-10/h4,10H,2-3H2,1H3
2D structure diagram/image available?
Yes
Cambridge Crystallographic Data Centre diagrams
Common Name Relationship Link
metronidazole -
General status
Veterinary substance type
Antibiotic, Antibacterial, Antiprotozoal
Substance groups
Imidazole
Minimum active substance purity
-
Known relevant impurities
-
Substance origin
Synthetic
Mode of action
Systemic. Metronidazole is reduced as it enters the target cell where it interacts with bacterial or protozoal DNA causing a loss of helical structure and strand breakage in the DNA leading to eventual death of the cell
Molecular targets
[DNA, binder], [Oxygen-insensitive NADPH nitroreductase, potentiator], [Periplasmic (Fe) hydrogenase 1, antagonist]
CAS RN
443-48-1
EC number
207-136-1
CIPAC number
-
US EPA chemical code
120401
PubChem CID
-
ATCvet Code
QJ01RA04
Therapeutic Class
Antiinfectants for systemic use: Antibacterials for systemic use
Controlled Drug?
No
Regulation 37/2010 MRL Classification
Prohibited
Molecular mass
171.15
PIN (Preferred Identification Name)
-
IUPAC name
2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethanol
CAS name
1-(β-hydroxyethyl)-2-methyl-5- nitroimidazole
Other status information
Evidence of use in third world countries
Relevant Environmental Water Quality Standards
-
Physical state
White to pale yellow crystalline solid
Formulations
Property
Product
Manufacturer
Authorisation Route
UK Legal Class
Example products using this active
Stomorgyl 10 Film-coated Tablets Merial Animal Health Ltd UK National authorisation Prescription only medicine to be authorised by a veterinarian (POM-V)
Stomorgyl 2 Film-coated Tablets Merial Animal Health Ltd UK National authorisation Prescription only medicine to be authorised by a veterinarian (POM-V)
Stomorgyl 20 Film-coated Tablets Merial Animal Health Ltd UK National authorisation Prescription only medicine to be authorised by a veterinarian (POM-V)
Formulation and application details
Usually supplied in tablet form for oral administration
ENVIRONMENTAL FATE
Property
Value
Source; quality score; and other information
Interpretation
Solubility - In water at 20 °C (mg l⁻¹)
9500
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
 High
Solubility - In organic solvents at 20 °C (mg l⁻¹)
5000
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
Ethanol		 -
500
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
Ether		 -
500
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
Chloroform		 -
Melting point (°C)
158
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
 -
Boiling point (°C)
- - -
Degradation point (°C)
- - -
Flashpoint (°C)
- - -
Octanol-water partition coefficient at pH 7, 20 °C
P
9.55 X 10-01 Calculated -
Log P
-0.02
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
 Low
Fat solubility of residues
Solubility
- - -
Data type
- - -
Density (g ml⁻¹)
- - -
Dissociation constant pKa) at 25 °C
2.38
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
 -
Strong acid
Vapour pressure at 20 °C (mPa)
0.04
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
 Low volatility
Henry's law constant at 25 °C (Pa m³ mol⁻¹)
- - -
Maximum UV-vis absorption L mol⁻¹ cm⁻¹
No absorption >290 nm
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
 -
Surface tension (mN m⁻¹)
- - -
Refractive Index
- - -
Degradation
Property
Value
Source; quality score; and other information
Interpretation
Soil degradation (days) (aerobic)
DT₅₀ (typical)
- - -
DT₅₀ (lab at 20 °C)
- - -
DT₅₀ (field)
- - -
DT₉₀ (lab at 20 °C)
- - -
DT₉₀ (field)
- - -
Note
-
Manure DT₅₀ (days)
16.1
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
soil-manure slurry mix Slightly persistent DT₅₀ range 9.7–26.8 days,		 -
Aqueous photolysis DT₅₀ (days) at pH 7
Value
- - -
Note
-
Aqueous hydrolysis DT₅₀ (days) at 20 °C and pH 7
Value
- - -
Note
-
Water-sediment DT₅₀ (days)
- - -
Water phase only DT₅₀ (days)
- - -
Soil adsorption and mobility
Property
Value
Source; quality score; and other information
Interpretation
Linear
Kd
-
R4 R = Peer reviewed scientific publications
4 = Verified data
 Mobile
Koc
47
Notes and range
General literature states Kd range 0.54-0.67 mL g⁻¹, Koc range 39-56 mL g⁻¹, soils=4
Freundlich
Kf
0.77
R4 R = Peer reviewed scientific publications
4 = Verified data
 Mobile
Kfoc
56.1
1/n
1.35
Notes and range
General literature Kf range 0.74-0.80 mL g⁻¹, Kfoc range 50.0-71.8 mL g⁻¹, 1.n range 1.27-1.43, soils=4
pH sensitivity
-
Fate indices
Property
Value
Source; quality score; and other information
Interpretation
GUS leaching potential index
- - -
Bio-concentration factor
BCF (l kg⁻¹)
- - -
CT₅₀ (days)
- -
Known soil and groundwater metabolites

None

Other known metabolites
Metabolite name and reference
Aliases
Formation medium / Rate
Estimated maximum occurrence fraction
Metabolising enzymes
2-hydroxy metronidazole - Humans/Animals (Liver) - -
1-acetic acid-2-methyl-5-nitroimidazole - - - -
1-(2-hydroxyethyl)-2-carboxylic acid-5-nitroimidazole salt - - - -
ECOTOXICOLOGY
Terrestrial ecotoxicology
Property
Value
Source; quality score; and other information
Interpretation
Mammals - Acute oral LD₅₀ (mg kg⁻¹)
> 500
F4 F = U.S. EPA ECOTOX database / U.S. EPA pesticide fate database / Miscellaneous WHO documents / FAO data, IPCS INCHEM data (US EPA Databases Related to Pesticide Risk Assessment )
4 = Verified data
Rat		 Moderate
Mammals - Short term dietary NOEL
(mg kg⁻¹)
- - -
(ppm diet)
- -
Mammals - Chronic 21d NOAEL (mg kg⁻¹ bw d⁻¹)
- - -
Birds - Acute LD₅₀ (mg kg⁻¹)
> 5000
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
Anas platyrhynchos		 Low
Birds - Short term dietary (LC₅₀/LD₅₀)
- - -
Birds - Chronic 21d NOEL (mg kg⁻¹ bw d⁻¹)
- - -
Earthworms - Acute 14 day LC₅₀ (mg kg⁻¹)
- - -
Earthworms - Chronic NOEC, reproduction (mg kg⁻¹)
- - -
Soil micro-organisms
- - -
Collembola
Acute LC₅₀ (mg kg⁻¹)
- - -
Chronic NOEC (mg kg⁻¹)
- - -
Non-target plants
- - -
- - -
Honeybees (Apis spp.)
Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
Unknown mode acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
Chronic
- - -
Bumblebees (Bombus spp.)
Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
-
Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
-
Mason bees (Osmia spp.)
Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)
- - -
Other bee species (1)
Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)
- - -
Mode of exposure
-
Other bee species (2)
Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)
- - -
Mode of exposure
-
Beneficial insects (Ladybirds)
- - -
Beneficial insects (Lacewings)
- - -
Beneficial insects (Parasitic wasps)
- - -
Beneficial insects (Predatory mites)
- - -
Beneficial insects (Ground beetles)
- - -
Aquatic ecotoxicology
Property
Value
Source; quality score; and other information
Interpretation
Fish - Acute 96 hour LC₅₀ (mg l⁻¹)
1060
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
Cyprinodon variegatus		 Low
Fish - Chronic 21 day NOEC (mg l⁻¹)
- - -
Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)
> 1000
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
Daphnia magna		 Low
Aquatic invertebrates - Chronic 21 day NOEC (mg l⁻¹)
- - -
Aquatic crustaceans - Acute 96 hour LC₅₀ (mg l⁻¹)
182
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
Americamysis bahia		 Low
Sediment dwelling organisms - Acute 96 hour LC₅₀ (mg l⁻¹)
- - -
Sediment dwelling organisms - Chronic 28 day NOEC, static, water (mg l⁻¹)
- - -
Sediment dwelling organisms - Chronic 28 day NOEC, sediment (mg kg⁻¹)
- - -
Aquatic plants - Acute 7 day EC₅₀, biomass (mg l⁻¹)
- - -
Algae - Acute 72 hour EC₅₀, growth (mg l⁻¹)
40.4
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
Pseudokirchneriella subcapitata		 Low
Algae - Chronic 96 hour NOEC, growth (mg l⁻¹)
- - -
Mesocosm study data
NOEAEC mg l⁻¹
- - -
NOEAEC mg l⁻¹
- - -
HUMAN HEALTH AND PROTECTION
General
Property
Value
Source; quality score; and other information
Interpretation
Threshold of Toxicological Concern (Cramer Class)
High (class III) - -
Mammals - Acute oral LD₅₀ (mg kg⁻¹)
> 500
F4 F = U.S. EPA ECOTOX database / U.S. EPA pesticide fate database / Miscellaneous WHO documents / FAO data, IPCS INCHEM data (US EPA Databases Related to Pesticide Risk Assessment )
4 = Verified data
Rat		 Moderate
Mammals - Dermal LD₅₀ (mg kg⁻¹ body weight)
- - -
Mammals - Inhalation LC₅₀ (mg l⁻¹)
- - -
Other Mammal toxicity endpoints
Subcutaneous LD₅₀ = 3640 mg kg⁻¹
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
Mouse		 -
Intraperitoneal LD₅₀ = 870 mg kg⁻¹
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
Mouse		 -
ADI - Acceptable Daily Intake (mg kg⁻¹ bw day⁻¹)
- - -
ARfD - Acute Reference Dose (mg kg⁻¹ bw day⁻¹)
- - -
AAOEL - Acute Acceptable Operator Exposure Level (mg kg⁻¹ bw day⁻¹)
- - -
AOEL - Acceptable Operator Exposure Level - Systemic (mg kg⁻¹ bw day⁻¹)
- - -
Dermal penetration studies (%)
- - -
Dangerous Substances Directive 76/464
- - -
Exposure Routes
Public
-
Occupational
-
Mammalian dose elimination route and rate
Eliminated with some hepatic metabolism mainly in the faeces but some also lost with urine
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
 -
Health issues
Specific human health issues
Carcinogen
Genotoxic
Endocrine disruptor
?Possibly, status not identified
A0 A = Chromosome aberration (EFSA database)
0 = No data
;
B0 B = DNA damage/repair (EFSA database)
0 = No data
;
C0 C = Gene mutation (EFSA database)
0 = No data
;
D0 D = Genome mutation (EFSA database)
0 = No data
;
E3 E = Unspecified genotoxicity type (miscellaneous data source)
3 = Negative
 No data found
Reproduction / development effects Acetyl cholinesterase inhibitor Neurotoxicant
?Possibly, status not identified
 No data found
✓Yes, known to cause a problem
Respiratory tract irritant Skin irritant Skin sensitiser
?Possibly, status not identified
✓Yes, known to cause a problem
 No data found
Eye irritant Phototoxicant  
?Possibly, status not identified
 No data found  
General human health issues
May cause headaches, nausea and diarrhoea
Associated with the development of leukopenia, neutropenia and increased risk of peripheral neuropathy
Published studies suggest substance is potentially carcinogenic; WHO & IARC - possible carcinogen; CLP data - inadequate epidemiological evidence so substance is not considered as a risk factor for cancer in humans; US NTP - suspected carcinogen; OSHA - Anticipated human carcinogen
Handling issues
Property
Value and interpretation
General
No information available
CLP classification 2013
-
WHO Classification
Not listed (Not listed)
UN Number
-
Waste disposal & packaging
-
Shelf-life, storage, stability and reactivity
-
TRANSLATIONS
Language
Name
English
metronidazole
French
-
German
-
Danish
-
Italian
-
Spanish
metronidazol
Greek
-
Polish
-
Swedish
-
Hungarian
-
Dutch
-
Norwegian
-
Record last updated: 12/10/2023
Contact: aeru@herts.ac.uk
Please cite as: Lewis, K.A., Tzilivakis, J., Warner, D. and Green, A. (2016) An international database for pesticide risk assessments and management. Human and Ecological Risk Assessment: An International Journal, 22(4), 1050-1064. DOI: 10.1080/10807039.2015.1133242