Clorsulon (Ref: MK-401)

Clorsulon (Ref: MK-401)	Last updated: 12/09/2025
(Also known as: MK-0401; L-631529)

GENERAL INFORMATION

Description

A benzenesulphonamide veterinary medication usually used in combination with ivermectin

Examples of veterinary uses

Used to control adult liver flukes in cattle, sheep and other livestock. Also used on domestic pets.

Examples of species treated

Domestic pets; Farm livestock particularly cattle, sheep

Approval status

VMR 2013/2033 approval status (GB/UK)

Approved - usually available as a prescription only medicine to be authorised by suitably qualified person (POM-VPS)

EU Regulatory approval status

Approved

Chemical structure

Isomerism

None

Chemical formula

C₈H₈Cl₃N₃O₄S₂

Canonical SMILES

C1=C(C(=CC(=C1N)S(=O)(=O)N)S(=O)(=O)N)C(=C(Cl)Cl)Cl

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

QOVTVIYTBRHADL-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C8H8Cl3N3O4S2/c9-7(8(10)11)3-1-4(12)6(20(14,17)18)2-5(3)19(13,15)16/h1-2H,12H2,(H2,13,15,16)(H2,14,17,18)

2D structure diagram/image available?

Yes

General status

Veterinary substance type

Antiparasitic

Substance groups

Sulphonamide

Minimum active substance purity

Known relevant impurities

Substance origin

Synthetic

Mode of action

Inhibits the enzymes phosphoglycerate kinase and phosphoglyceromutase

Molecular targets

[Phosphoglycerate kinase, Inhibitor], [ Phosphoglyceromutase enzyme, Inhibitor]

CAS RN

60200-06-8

EC number

262-100-2

CIPAC number

US EPA chemical code

PubChem CID

Therapeutic Class

Antiparasitic products, insecticides & repellents: Endectocides

ATCvet Code

QP54AA51

Controlled Drug?

Regulation 37/2010 MRL Classification

Molecular mass

380.66

PIN (Preferred Identification Name)

IUPAC name

4-amino-6-(1,2,2-trichloroethenyl)benzene-1,3-disulfonamide

CAS name

4-amino-6-(trichloroethenyl)-1,3-benzenedisulfonamide

Forever chemical

Other status information

Relevant Environmental Water Quality Standards

Physical state

White to off-white crystalline powder

Related substances & organisms

ivermectin

Commercial

Property

Value

Availability status

Current

Introduction & key dates

1985, first registered in USA

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

Chanelle Animal Health Ltd
Boehringer Ingelheim Animal Health UK Ltd
Virbac Ltd

Example products using this active

Curatrem
Animec Super Solution for Injection
Ivomac Super Solution for Injection

Formulation and application details

Often formulated in combination with ivermectin as a solution for injection

Commercial production

The production of clorsulon involves a multi-step organic synthesis starting from m-nitrobenzaldehyde and chloroform. These precursors undergo a series of reactions including condensation, chlorination, and elimination, followed by reduction using iron powder in an acidic medium to form key intermediates. The process continues with chlorosulfonation, introducing sulfonyl groups to the aromatic ring, and finally amination, where ammonia reacts with the sulfonyl chloride intermediates to yield the final compound, clorsulon.

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)

800

Moderate

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

17050

DMSO

7000

Ethanol

Melting point (°C)

203

Boiling point (°C)

Degradation point (°C)

205

Flashpoint (°C)

348

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

1.51 X 10⁰¹

Calculated

Log P

1.18

Low

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

Dissociation constant pKa) at 25 °C

Vapour pressure at 20 °C (mPa)

1.0 X 10^-13

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)

19.6

Non-persistent

DT₅₀ (lab at 20 °C)

DT₅₀ (field)

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

Note

Manure DT₅₀ (days)

32.2

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)

1.40

Mobile

K_oc (mL g⁻¹)

30.8

Notes and range

Freundlich

K_f (mL g⁻¹)

1.57

K_foc (mL g⁻¹)

¹/_n

1.06

Notes and range

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

3.25

Calculated

High leachability

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)

> 10000

Rat

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 dw soil)

1000

Eisenia foetida

Moderate

Earthworms - Chronic NOEC, reproduction (mg kg⁻¹ dw soil)

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)

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

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

560

Poecilia reticulata

Low

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

1144

Daphnia magna

Low

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

Daphnia magna

Low

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)

570

Raphidocelis subcapitata

Low

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

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)

> 10000

Rat

Low

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

Mammals - Inhalation LC₅₀ (mg l⁻¹)

Other Mammal toxicity endpoints

Intraperitoneal LD₅₀ = 808 mg kg⁻¹

Rat

ADI - Acceptable Daily Intake (mg kg⁻¹ bw day⁻¹)

0.002

Dog SF=1000

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

Rapidly excreted in the faeces of animals

Health issues

Specific human health issues (hazard-based)

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

Possible thyroid and liver toxicant
Weak evidence to suggest substance is carcinogenic

Handling issues

Property

Value and interpretation

General

No information available

CLP classification 2013

Human: H319, H373

WHO Classification

Not listed (Not listed)

UN Number

Not regulated

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

Stable > 4 yrs; Not highly reactive

TRANSLATIONS

Language

Name

English

clorsulon

French

clorsulone

German

Danish

Italian

Spanish

clorsulon

Greek

Polish

Swedish

Hungarian

Dutch

Norwegian

Record last updated:	12/09/2025
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