Ponazuril (Ref: Bay Vi 9143)

Ponazuril (Ref: Bay Vi 9143)	Last updated: 16/09/2025
(Also known as: Toltrazuril sulfone)

GENERAL INFORMATION

Description

A medicinal triazine-based veterinary drug used as antiprotozoal treatment

Examples of veterinary uses

Used to treat protozoal myeloencephalitis (EPM), caused by Sarcocystis neurona and various other parasitic conditions including coccidia

Examples of species treated

Horses; Cats; Dogs; Piglets; Cattle; Goats; Llamas

Approval status

VMR 2013/2033 approval status (GB/UK)

Not approved

EU Regulatory approval status

Not approved

Chemical structure

Isomerism

Ponazuril exhibits structural isomerism, but not stereoisomerism, based on its chemical configuration. It is a triazine-based compound derived from toltrazuril, and its structure includes a trifluoromethylsulfonyl phenoxy group attached to a substituted triazine ring. The molecule is rigid and symmetrical, and its functional groups do not create chiral centres, meaning it does not form enantiomers or diastereomers. Instead, any isomerism associated with ponazuril stems from positional isomers or tautomers that could theoretically arise during synthesis or degradation, though these are not pharmacologically relevant in its approved veterinary formulations.

Chemical formula

C₁₈H₁₄F₃N₃O₆S

Canonical SMILES

CC1=C(C=CC(=C1)N2C(=O)NC(=O)N(C2=O)C)OC3=CC=C(C=C3)S(=O)(=O)C(F)(F)F

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

VBUNOIXRZNJNAD-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C18H14F3N3O6S/c1-10-9-11(24-16(26)22-15(25)23(2)17(24)27)3-8-14(10)30-12-4-6-13(7-5-12)31(28,29)18(19,20)21/h3-9H,1-2H3,(H,22,25,26)

2D structure diagram/image available?

Yes

General status

Veterinary substance type

Coccidiostat, Antiparasitic, Antiprotozoal

Substance groups

Triazinetrione

Minimum active substance purity

>95%

Known relevant impurities

Substance origin

Synthetic

Mode of action

Acts by inhibiting mitochondrial respirayion and nuclear pyrimidine synthesis in the parasite

Molecular targets

[Mitochondrial respiration, Inhibitor]

CAS RN

69004-04-2

EC number

CIPAC number

US EPA chemical code

PubChem CID

Therapeutic Class

Antiprotozoals: Triazines

ATCvet Code

QP51AJ04

Controlled Drug?

Regulation 37/2010 MRL Classification

Molecular mass

457.38

PIN (Preferred Identification Name)

1-methyl-3-(3-methyl-4-(4-(trifluoromethylsulfonyl)phenoxy)phenyl)-1,3,5-triazinane-2,4,6-trione

IUPAC name

1-methyl-3-(3-methyl-4-(4-(trifluoromethylsulfonyl)phenoxy)phenyl)-1,3,5-triazinane-2,4,6-trione

CAS name

Forever chemical

Other status information

Relevant Environmental Water Quality Standards

Physical state

Off-white coloured powder

Related substances & organisms

toltrazuril

Commercial

Property

Value

Availability status

Current

Introduction & key dates

Late 20th century, developed; 1990s, start of animal use; 2010, off-label use for pets; 2013, not approved UK

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

Bayer Corporation

Example products using this active

Marquis

Formulation and application details

Usually supplied as an oral paste, suspension, or compounded solution, depending on the species and treatment context.

Commercial production

Ponazuril is synthesised through a multi-step process that builds on the chemical structure of toltrazuril, its parent compound. The production begins with the formation of 3-methyl-4-(4-phenoxytrifluoromethylsulfide)-nitrobenzene, which is then reduced to the corresponding aniline derivative. This intermediate undergoes further transformation into a phenyl isocyanate, which reacts with cyanuric chloride or similar triazine precursors to form the triazine-2,4,6-trione ring system, a hallmark of ponazuril’s structure.

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)

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

Melting point (°C)

Boiling point (°C)

Degradation point (°C)

Flashpoint (°C)

93.3

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

Log P

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

Dissociation constant pKa) at 25 °C

Vapour pressure at 20 °C (mPa)

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)

500

Very persistent

DT₅₀ (lab at 20 °C)

DT₅₀ (field)

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

Note

General literature cites the subtsance as being highly persistent with a DT₅₀ of > 1 year

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)

K_oc (mL g⁻¹)

Notes and range

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)

980

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)

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)

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)

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)

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)

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

980

Rat

Moderate

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

Mammals - Inhalation LC₅₀ (mg l⁻¹)

Other Mammal toxicity endpoints

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 via the faeces

Health issues

Specific human health issues

Carcinogen

Genotoxic

Endocrine disruptor

No data found

; ; ; ;

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 gastro-intestinal disturbance including vomiting and diarrhoea

Handling issues

Property

Value and interpretation

General

Not explosive
Incompatible with oxidising agents
Will emit toxic gases when heated to decomposition including hydrocyanic acid and hydrogen fluoride

CLP classification 2013

WHO Classification

Not listed (Not listed)

UN Number

None allocated

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

ponazuril

French

ponazuril

German

Ponazuril

Danish

Italian

Spanish

Ponazurilo

Greek

Polish

Swedish

Hungarian

Dutch

Norwegian

Record last updated:	16/09/2025
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