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Trimethoprim
Last updated: 17/05/2024
(Also known as: TRI; TMP; trimexazole; SMX-TMP)
GENERAL INFORMATION
Description
A synthetic bacteriostatic antibiotic used as a veterinary medicine active against both gram-positive and gram-negative bacteria
Availability status
Current
Introduction & key dates
circa 1965, discovered; 1973, approved
Examples of veterinary uses
Used to treat infections of the respiratory tract, urogenital tract, alimentary tract, skin joints and wound
Examples of species treated
Cats; Dogs; Horses; Cattle; Pigs; Turkeys; Sheep
Approval status
VMR 2013/2033 approval status (GB/UK)
Approved
EU Regulatory approval status
Approved
Chemical structure
Isomerism
-
Chemical formula
C₁₄H₁₈N₄O₃
Canonical SMILES
COC1=CC(=CC(=C1OC)OC)CC2=CN=C(N=C2N)N
Isomeric SMILES
No data
International Chemical Identifier key (InChIKey)
IEDVJHCEMCRBQM-UHFFFAOYSA-N
International Chemical Identifier (InChI)
InChI=1S/C14H18N4O3/c1-19-10-5-8(6-11(20-2)12(10)21-3)4-9-7-17-14(16)18-13(9)15/h5-7H,4H2,1-3H3,(H4,15,16,17,18)
2D structure diagram/image available?
Yes
Cambridge Crystallographic Data Centre diagrams
Common Name Relationship Link
trimethoprim -
General status
Veterinary substance type
Antibiotic, Antibacterial, Medicinal drug, Medicated feed additive
Substance groups
Diaminopyrimidine
Minimum active substance purity
-
Known relevant impurities
-
Substance origin
Synthetic
Mode of action
Interferes with the action of bacterial dihydrofolate reductase, inhibiting synthesis of tetrahydrofolic acid
Molecular targets
[Thymidylate synthase, Antagonist], [Dihydrofolate reductase, Antagonist]
CAS RN
738-70-5
EC number
212-006-2
CIPAC number
-
US EPA chemical code
-
PubChem CID
-
Therapeutic Class
Antiinfectants for systemic use: Antibacterials for intramammary use, Antibacterials for systemic use
ATCvet Code
QJ51EA01; QJ01EA01
Controlled Drug?
No
Regulation 37/2010 MRL Classification
Allowed substance (Table 1: Equidae, All food producing species)
Molecular mass
290.32
PIN (Preferred Identification Name)
-
IUPAC name
5-(3,4,5- trimethoxybenzyl) pyrimidine-2,4-diamine
CAS name
2,4-diamino-5-(3,4,5-trimethoxybenzyl)pyrimidine
Other status information
-
Relevant Environmental Water Quality Standards
-
Physical state
White to cream coloured crystalline powder
Related substances & organisms
Formulations
Property
Product
Manufacturer
Authorisation Route
Legal Class (GB/UK)
Example products (past and present) using this active
Bimotrim Solution for Injection Bimeda Animal Health Ltd UK National authorisation Prescription only medicine to be authorised by a veterinarian (POM-V)
Diatrim Oral Powder Eurovet Animal Health B.V. GB National authorisation Prescription only medicine to be authorised by a veterinarian (POM-V)
Metaxol Solution for Drinking Water Eurovet Animal Health B.V. GB National authorisation Prescription only medicine to be authorised by a veterinarian (POM-V)
Norodine Bolus Tablets Norbrook Laboratories Ltd UK National authorisation (IC) Prescription only medicine to be authorised by a veterinarian (POM-V)
Formulation and application details
Available in a variety of formulations including tablets, oral pastes, medicated premix feeds, additives for drinking water and solutions for injection
ENVIRONMENTAL FATE
Property
Value
Source; quality score; and other information
Interpretation
Solubility - In water at 20 °C (mg l⁻¹)
400
R4 R = Peer reviewed scientific publications
4 = Verified data
 Moderate
Solubility - In organic solvents at 20 °C (mg l⁻¹)
18200
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Chloroform		 -
25700
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Propylene glycol		 -
30
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Ether		 -
20
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
Benzene		 -
Melting point (°C)
201
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
 -
Boiling point (°C)
- - -
Degradation point (°C)
- - -
Flashpoint (°C)
- - -
Octanol-water partition coefficient at pH 7, 20 °C
P
8.13 X 1000 Calculated -
Log P
0.91
R4 R = Peer reviewed scientific publications
4 = Verified data
 Low
Fat solubility of residues
Solubility
- - -
Data type
- - -
Density (g ml⁻¹)
- - -
Dissociation constant pKa) at 25 °C
7.12
R4 R = Peer reviewed scientific publications
4 = Verified data
 -
Weak base
Vapour pressure at 20 °C (mPa)
1.31 X 10-03
R4 R = Peer reviewed scientific publications
4 = Verified data
 Low volatility
Henry's law constant at 25 °C (Pa m³ mol⁻¹)
- - -
Volatilisation as max % of applied dose lost
From plant surface
- - -
From soil surface
- - -
Maximum UV-vis absorption L mol⁻¹ cm⁻¹
- - -
Surface tension (mN m⁻¹)
- - -
Refractive Index
- - -
Environmental release
Substance may enter the environment via the urine and faeces of treated animals
Degradation
Property
Value
Source; quality score; and other information
Interpretation
Soil degradation (days) (aerobic)
DT₅₀ (typical)
110
R4 R = Peer reviewed scientific publications
4 = Verified data
 Persistent
DT₅₀ (lab at 20 °C)
- - -
DT₅₀ (field)
- - -
DT₉₀ (lab at 20 °C)
- - -
DT₉₀ (field)
- - -
Note
-
Manure DT₅₀ (days)
31.5
R4 R = Peer reviewed scientific publications
4 = Verified data
Sewage sludge DT59 range 22-41 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)
- - -
Air degradation
As this parameter is not normally measured directly, a surrogate measure is used: ‘Photochemical oxidative DT₅₀’. Where data is available, this can be found in the Fate Indices section below.
Decay in stored produce DT₅₀
-
Soil adsorption and mobility
Property
Value
Source; quality score; and other information
Interpretation
Linear
Kd (mL g⁻¹)
-
R4 R = Peer reviewed scientific publications
4 = Verified data
 Slightly mobile
Koc (mL g⁻¹)
2835
Notes and range
General literature states Koc range 1680-3990 mL g⁻¹
Freundlich
Kf (mL g⁻¹)
- - -
Kfoc (mL g⁻¹)
-
1/n
-
Notes and range
-
pH sensitivity
-
Fate indices
Property
Value
Source; quality score; and other information
Interpretation
GUS leaching potential index
1.12 Calculated Low leachability
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
- 1-N-oxide metabolite Animals -
- 3-N-oxide metabolite Animals -
- 4-hydroxy metabolite Animals -
- 3-hydroxy metabolite Animals -
ECOTOXICOLOGY
Terrestrial ecotoxicology
Property
Value
Source; quality score; and other information
Interpretation
Mammals - Acute oral LD₅₀ (mg kg⁻¹)
4850
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
Mouse		 Low
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)
- - -
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
Temperate Freshwater Fish - Acute 96 hour LC₅₀ (mg l⁻¹)
> 100
R4 R = Peer reviewed scientific publications
4 = Verified data
Oryzias latipes		 Low
Temperate Freshwater Fish - Chronic 21 day NOEC (mg l⁻¹)
- - -
Tropical Freshwater Fish - Acute 96 hour LC₅₀ (mg l⁻¹)
- - -
Temperate Freshwater Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)
123
R3 R = Peer reviewed scientific publications
3 = Unverified data of known source
Daphnia magna		 Low
Temperate Freshwater Aquatic invertebrates - Chronic 21 day NOEC (mg l⁻¹)
- - -
Tropical Freshwater Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)
- - -
Aquatic crustaceans - Acute 96 hour LC₅₀ (mg l⁻¹)
- - -
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)
> 1.0
R4 R = Peer reviewed scientific publications
4 = Verified data
Lemna gibba LOEC 7 day		 Moderate
Algae - Acute 72 hour EC₅₀, growth (mg l⁻¹)
80.3
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
Selenastrum capricornutum		 Low
Algae - Chronic 96 hour NOEC, growth (mg l⁻¹)
25.5
R4 R = Peer reviewed scientific publications
4 = Verified data
Selenastrum capricornutum		 Low
Mesocosm study data
NOEAEC mg l⁻¹
- - -
NOEAEC mg l⁻¹
- - -
Marine bivalves
- - -
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)
4850
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
Mouse		 Low
Mammals - Dermal LD₅₀ (mg kg⁻¹ body weight)
- - -
Mammals - Inhalation LC₅₀ (mg l⁻¹)
- - -
Other Mammal toxicity endpoints
Intraperitoneal LD₅₀ = 500 mg kg⁻¹
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
Rat		 -
Subcutaneous LD₅₀ > 5000 mg kg⁻¹
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
Rat		 -
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
Up to 20% of dose is metabolised in the liver and is excreted unchanged in the urine and faeces
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
 -
Health issues
Specific human health issues
Carcinogen
Genotoxic
Endocrine disruptor
No data found
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
;
E0 E = Unspecified genotoxicity type (miscellaneous data source)
0 = No data
 No data found
Reproduction / development effects Acetyl cholinesterase inhibitor Neurotoxicant
?Possibly, status not identified
 No data found
?Possibly, status not identified
Respiratory tract irritant Skin irritant Skin sensitiser
No data found
✓Yes, known to cause a problem
 No data found
Eye irritant Phototoxicant  
No data found No data found  
General human health issues
May cause nausea and vomiting
May cause disturbance in the production of blood cells
Mmay cause hyperkalaemia
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
trimethoprim
French
trimethoprime
German
-
Danish
-
Italian
-
Spanish
trimetoprima
Greek
-
Polish
trimetoprim
Swedish
-
Hungarian
-
Dutch
-
Norwegian
-
Record last updated: 17/05/2024
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