Sulphadimethoxine

Sulphadimethoxine	Last updated: 15/09/2025
(Also known as: sulfadimethoxine; sulfadimetoxin; SDM)

GENERAL INFORMATION

Description

Broad spectrum sulphonamide drug with veterinary applications which is usually formulated as the sodium salt.

Examples of veterinary uses

Used to treat a variety of infections including those of the respiratory tract, urinary tract and soft tissue infections. It is also used for the treatment of coccidiosis.

Examples of species treated

Dogs; Horses; Cattle; Birds; Cats; Dogs; Poultry; Pigs; Sheep

Approval status

VMR 2013/2033 approval status (GB/UK)

Approved - usually available as a prescription only medicine to be authorised by a veterinarian (POM-V)

EU Regulatory approval status

Approved

Chemical structure

Isomerism

Sulphadimethoxine primarily exhibits tautomeric isomerism, a form of structural isomerism where the molecule can exist in equilibrium between different protonation states. This occurs within its pyrimidine ring, which contains nitrogen atoms capable of shifting a hydrogen atom between positions, leading to amino–imino tautomerism. These tautomers differ in the placement of double bonds and hydrogen atoms but retain the same molecular formula.

Chemical formula

C₁₂H₁₄N₄O₄S

Canonical SMILES

COC1=NC(=NC(=C1)NS(=O)(=O)C2=CC=C(C=C2)N)OC

Isomeric SMILES

International Chemical Identifier key (InChIKey)

ZZORFUFYDOWNEF-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C12H14N4O4S/c1-19-11-7-10(14-12(15-11)20-2)16-21(17,18)9-5-3-8(13)4-6-9/h3-7H,13H2,1-2H3,(H,14,15,16)

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
sulphadimethoxine	-

General status

Veterinary substance type

Antibiotic, Antibacterial, Antiprotozoal, Coccidiostat, Antiparasitic, Medicinal drug

Substance groups

Sulphonamide

Minimum active substance purity

Known relevant impurities

Substance origin

Synthetic

Mode of action

Inhibits the conversion of para-aminobenzoic acid to dihydrofolic acid and so inhibits bacterial synthesis

Molecular targets

[Cytochrome P450 2C9, Inhibitor]

CAS RN

122-11-2

EC number

204-523-7

CIPAC number

US EPA chemical code

PubChem CID

Therapeutic Class

Antiinfectants for systemic use: Antibacterials for systemic use, Antiprotozoals

ATCvet Code

QJ01EQ09; QP51AG02

Controlled Drug?

Regulation 37/2010 MRL Classification

Allowed substance (Table 1: All food producing species)

Molecular mass

310.33

PIN (Preferred Identification Name)

IUPAC name

4-amino-N-(2,6-dimethoxypyrimidin-4-yl)benzenesulfonamide

CAS name

4-amino-N-(2,6-dimethoxy-4-pyrimidinyl)benzolsulfonamid

Forever chemical

Other status information

Relevant Environmental Water Quality Standards

Physical state

White powder

Related substances & organisms

sulphadimethoxine sodium

Commercial

Property

Value

Availability status

Current

Introduction & key dates

1950-1970, initial registrations globally; Early 2000s, withdrawn EU

Example manufacturers & suppliers of products using this active now or historically

Wuhan Fortuna Chemical Co. Ltd.
Raman Pharma

Example products using this active

Albon
Di-Methox

Formulation and application details

Usually supplied as the sodium salt liquid suspension in sachets and given orally but also available in tablet form and solutions for injection

Commercial production

The production of sulphadimethoxine typically involves a multi-step chemical synthesis starting with a condensation reaction between 4-aminobenzenesulfonamide and 2,6-dimethoxy-4-chloropyrimidine. This reaction is carried out in a methanol solution with sodium hydroxide at elevated temperatures for several hours to form the crude product. After the reaction is complete, the mixture is cooled and acidified with hydrochloric acid to adjust the pH, which precipitates the intermediate compound. The crude product is then purified by recrystallisation.

Impact on climate of production and use

Published GHG data is not available for most pharmaceuticals. However, according to industry, global averages suggest producing 1 kg of a typical active pharmaceutical ingredient can range from 10 to 100 kg CO₂e for small molecule drugs and potentially up to 1000 kg CO₂e for complex biologicals such as vaccines, depending on the drug type, its formulation, complexity of synthesis, solvent recovery, and energy sources used.

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

Solubility - In water at 20 °C (mg l⁻¹)

343

Moderate

Solubility - In organic solvents at 20 °C (mg l⁻¹)

Melting point (°C)

200

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

Flashpoint (°C)

Octanol-water partition coefficient at pH 7, 20 °C

4.27 X 10⁰⁰

Calculated

Log P

0.63

Low

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

Dissociation constant pKa) at 25 °C

5.54

Vapour pressure at 20 °C (mPa)

2.11 X 10^-04

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

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)

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)

Sediment 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

K_d (mL g⁻¹)

Slightly mobile

K_oc (mL g⁻¹)

1672

Notes and range

K_oc 2517 mL g⁻¹ soil with 81.5% sand, 4856 mL g⁻¹ soil with 52% sand

Freundlich

K_f (mL g⁻¹)

K_foc (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

Bio-concentration factor

BCF (l kg⁻¹)

CT₅₀ (days)

Known metabolites

None

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 1000

Rabbit

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)

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

Vegetative vigour ER₅₀ (g ha⁻¹)

Seedling emergence ER₅₀ (g ha⁻¹)

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

Notes

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)

> 400

Oncorhynchus mykiss

Low

Temperate Freshwater Fish - Chronic 21 day NOEC (mg l⁻¹)

Tropical Freshwater Fish - Acute 96 hour LC₅₀ (mg l⁻¹)

> 1000

Danio rerio

Low

Temperate Freshwater Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)

189

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 (free-floating, fonds growth, fresh) - 7 day (mg l⁻¹)

Aquatic plants (rooted, growth rate, fresh) - 14 day (mg l⁻¹)

Algae - Acute (growth rate, fresh; mg l⁻¹) (EC₅₀)

2.3

Raphidocelis subcapitata

Moderate

Algae - Chronic (growth rate, fresh; mg l⁻¹) (NOEC)

0.53

Raphidocelis subcapitata

Moderate

Mesocosm study data

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)

> 1000

Rabbit

Moderate

Mammals - Dermal LD₅₀ (mg kg⁻¹ body weight)

Mammals - Inhalation LC₅₀ (mg l⁻¹)

Other Mammal toxicity endpoints

Intravenous LD₅₀ = 1000 mg kg⁻¹

Rabbit

Subcutaneous LD₅₀ = 791 mg kg⁻¹

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

Metabolised and excreted mainly in the urine

Health issues

Specific human health issues

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

No data found

Reproduction / development effects

Acetyl cholinesterase inhibitor

Neurotoxicant

No data found

Respiratory tract irritant

Skin irritant

Skin sensitiser

No data found

Eye irritant

Phototoxicant

No data found

General human health issues

May cause vomiting and diarrhoea
Possible kidney and liver toxicant

Handling issues

Property

Value and interpretation

General

Hygroscopic

CLP classification 2013

WHO Classification

Not listed (Not listed)

UN Number

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

sulphadimethoxine

French

German

Danish

Italian

sulfadimetossina

Spanish

sulfametoxina

Greek

Polish

Swedish

Hungarian

Dutch

Norwegian

Record last updated:	15/09/2025
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