Pyriproxyfen (Ref: S 9318)

Pyriproxyfen (Ref: S 9318)	Last updated: 04/09/2025
(Also known as: pyriproxifen)

GENERAL INFORMATION

Description

An insect growth regulator with potent activity against developing stages of fleas

Examples of veterinary uses

Used mainly for flea control on domestic pets.

Examples of species treated

Cats; Dogs

Approval status

VMR 2013/2033 approval status (GB/UK)

Not approved

EU Regulatory approval status

Not approved

Chemical structure

Isomerism

Pyriproxyfen exhibits stereoisomerism due to the presence of a single chiral centre in its molecular structure. This means it can exist as two enantiomers. The technical-grade pyriproxyfen used in insecticidal formulations is typically an isomeric mixture.

Chemical formula

C₂₀H₁₉NO₃

Canonical SMILES

CC(COC1=CC=C(C=C1)OC2=CC=CC=C2)OC3=CC=CC=N3

Isomeric SMILES

International Chemical Identifier key (InChIKey)

NHDHVHZZCFYRSB-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C20H19NO3/c1-16(23-20-9-5-6-14-21-20)15-22-17-10-12-19(13-11-17)24-18-7-3-2-4-8-18/h2-14,16H,15H2,1H3

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
pyriproxyfen	-

General status

Veterinary substance type

Insecticide, Veterinary hygiene

Substance groups

Juvenile hormone mimic insecticide

Minimum active substance purity

970 g kg⁻¹ racemic mixture

Known relevant impurities

EU dossier - toluene 5g kg⁻¹

Substance origin

Synthetic

Mode of action

A juvenile hormone mimic. Pyriproxyfen mimics the natural hormone that regulates development and reproduction in insects. By binding to the Met receptor, it disrupts normal hormonal signalling, leading to impaired metamorphosis, sterilization, and inhibition of egg development.

Molecular targets

[Methoprene-tolerant (Met) protein, Receptor]

CAS RN

95737-68-1

EC number

429-800-1

CIPAC number

715

US EPA chemical code

129032

PubChem CID

91753

CLP index number

613-303-00-3

Therapeutic Class

Antiparasitic products, insecticides & repellents: Ecoparasiticides, insecticides & repellents

ATCvet Code

QP53AC54

Controlled Drug?

Regulation 37/2010 MRL Classification

Molecular mass

321.37

PIN (Preferred Identification Name)

IUPAC name

4-phenoxyphenyl (RS)-2-(2-pyridyloxy)propyl ether

CAS name

2-(1-methyl-2-(4-phenoxyphenoxy)ethoxy)pyridine

Forever chemical

Other status information

Relevant Environmental Water Quality Standards

Physical state

White granule solid

Commercial

Property

Value

Availability status

Current

Introduction & key dates

1995, first registered for agricultural use Japan

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

Sumitomo
Syngenta
BePharm Ltd.
Bayer plc
Alfamed S.A.S.

Example products using this active

Admiral
Juvinal
Atominal
Pyriproxyfen 10EC
Distance IGR
Fleeguard Spot-On Solution
Bob Martin Vetcare Spot-On 10 % for Cats and Kittens

Formulation and application details

Usually supplied as an emulsifiable concentrate that is mixed with water and applied as a foliar spray for crops. Also available as bait, spot-on treatments and wettable powders for animal health.

Commercial production

The production of pyriproxyfen involves a two-step synthesis starting from 4-phenoxyphenol. First, this compound reacts with propylene oxide in the presence of a basic catalyst such as potassium hydroxide or sodium hydroxide, using water as the solvent, yielding the intermediate 1-(4-phenoxyphenoxy)-2-propanol. In the second step, this intermediate is reacted with 2-chloropyridine in a solvent like dioxane or N-methylpyrrolidone, again under basic conditions and elevated temperatures. After completion, the mixture is filtered and the solvent evaporated to isolate crude pyriproxyfen, which can then be purified.

Impact on climate of production and use

Data for the amount of life cycle GHGs produced by pyriproxyfen are not available in the public domain. However, whilst estimates vary, more general data suggests that between 14 and 19 kilograms of CO₂e is emitted per kilogram of insecticide produced.

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

0.37

Low

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

27000

n-Heptane

27000

Methanol

1000000

Acetone

1000000

Ethyl acetate

Melting point (°C)

Boiling point (°C)

318

Degradation point (°C)

318

Flashpoint (°C)

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

2.34 X 10⁰⁵

Calculated

Log P

5.37

High

Fat solubility of residues

Solubility

Soluble

Data type

Regulatory data - observed in metabolism and farm animal feeding studies

Density (g ml⁻¹)

1.26

Dissociation constant pKa) at 25 °C

6.87

Weak acid

Vapour pressure at 20 °C (mPa)

1.33 X 10^-02

Low volatility

Henry's law constant at 25 °C (Pa m³ mol⁻¹)

1.16 X 10^-02

Non-volatile

Volatilisation as max % of applied dose lost

From plant surface

From soil surface

Maximum UV-vis absorption L mol⁻¹ cm⁻¹

Neutral solution 271nm = 6649
Acidic solution 278nm = 10354
Basic solution 271nm = 6749

Surface tension (mN m⁻¹)

Refractive Index

1.5823

Environmental release

Degradation

Property

Value

Source; quality score; and other information

Interpretation

Soil degradation (days) (aerobic)

DT₅₀ (typical)

Non-persistent

DT₅₀ (lab at 20 °C)

6.7

Non-persistent

DT₅₀ (field)

4.2

Non-persistent

DT₉₀ (lab at 20 °C)

24.5

Non-persistent

DT₉₀ (field)

14.7

Note

EU dossier lab studies DT₅₀ range 2.8-20.4 days, DT₉₀ range 9.2-54 days; Field studies DT₅₀ range 3.5-5.9 days, DT₉₀ range 12-20 days

Manure DT₅₀ (days)

Aqueous photolysis DT₅₀ (days) at pH 7

Value

11.5

Moderately fast

Note

Natural light, 43N

Aqueous hydrolysis DT₅₀ (days) at 20 °C and pH 7

Value

Stable

Note

Stable pH 4 to pH 9, 50 °C

Water-sediment DT₅₀ (days)

6.5

Fast

Water phase only DT₅₀ (days)

1.6

Moderately fast

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

[Sweet pepper: No residue decay after 30 days in cold, dark storage; Field study], [Peppers: 718 days @ 4 DegC]

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)

227

Non-mobile

K_foc (mL g⁻¹)

21175

¹/_n

1.15

Notes and range

EU dossier K_f range 126-324 mL g⁻¹, K_foc range 11000-34200 mL g⁻¹, ¹/_n range 1.1-1.2, Soils=4

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

-0.20

Calculated

Low leachability

Bio-concentration factor

BCF (l kg⁻¹)

1379

Threshold for concern

CT₅₀ (days)

0.9

Known soil metabolites

Metabolite

Major/Minor fraction

$Click here for further information on Major/Minor fraction$

Estimated maximum occurrence fraction

Notes

(RS)-2-(2-pyridyloxy)propionic acid

Minor fraction

0.086

4-hydroxyphenyl (RS)-2-(2-pyridyloxy)propyl ether

Minor fraction

0.020

4-(4-hydroxyphenoxy)phenyl (RS)-2-(2-pyridyloxy)propyl ether

Minor fraction

0.063

Known groundwater metabolites

None

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

4-hydroxyphenyl (RS)-2-(2-pyridyloxy)propyl ether
Note: Koc = 10mL/g; DT50 ~ 1000 days (industry data)

DPH-pyr

Surface water

(RS)-2-hydroxypropyl 4-phenoxyphenyl ether

POPA

Plant

2-hydroxypyridin

2-OH-PY

Plant

(RS)-2-(2-pyridyloxy)propyl alcohol

PYPA

Plant

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 5000

Rat

Low

Mammals - Short term dietary NOEL

(mg kg⁻¹)

> 24

Rat 6 mnth

High

(ppm diet)

> 400

Mammals - Chronic 21d NOAEL (mg kg⁻¹ bw d⁻¹)

Birds - Acute LD₅₀ (mg kg⁻¹)

> 1906

Colinus virginianus

Moderate

Birds - Short term dietary (LC₅₀/LD₅₀)

> 863 mg kg bw⁻¹ day⁻¹

Colinus virginianus

Birds - Chronic 21d NOEL (mg kg⁻¹ bw d⁻¹)

Earthworms - Acute 14 day LC₅₀ (mg kg⁻¹)

> 500

Eisenia foetida corr

Moderate

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)

Apis mellifera

Moderate

Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

> 100

Apis mellifera

Low

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) as Mortality LR₅₀ g ha⁻¹, Extended lab study

> 225

Chrysoperla carnea

Low

Beneficial insects (Parasitic wasps) as Mortality LR₅₀ g ha⁻¹ 48 hr, Std lab test

213

Aphidius rhopalosiphi

Low

Beneficial insects (Predatory mites) as Mortality LR₅₀ g ha⁻¹ 7 day, Std lab test

Typhlodromus pyri

Moderate

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)

> 0.27

Lepomis macrochirus

Moderate

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

0.0043

Oncorhynchus mykiss

High

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

8.40

Danio rerio EC₅₀ Embryo

Moderate

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

0.4

Daphnia magna

Moderate

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

0.000015

Daphnia magna

High

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

Aquatic crustaceans - Acute 96 hour LC₅₀ (mg l⁻¹)

0.047

Americamysis bahia

High

Sediment dwelling organisms - Acute 96 hour LC₅₀ (mg l⁻¹)

Sediment dwelling organisms - Chronic 28 day NOEC, static, water (mg l⁻¹)

0.01

Chironomus riparius Emergence

Moderate

Sediment dwelling organisms - Chronic 28 day NOEC, sediment (mg kg⁻¹)

Aquatic Plants (free-floating, fonds growth, fresh) - 7 day (mg l⁻¹) (EC₅₀, Semi-static)

> 0.18

Lemna gibba 14 day

Moderate

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

Algae - Acute (growth rate, fresh; mg l⁻¹) (72 hr ErC₅₀, Static)

0.150

Raphidocelis subcapitata

Moderate

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

Mesocosm study data

NOEAEC mg l⁻¹

0.005

Aquatic community

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)

> 5000

Rat

Low

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

2000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 1.3

Rat 4 hr (whole body)

Other Mammal toxicity endpoints

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

0.05

ARfD - Acute Reference Dose (mg kg⁻¹ bw day⁻¹)

1.0

AAOEL - Acute Acceptable Operator Exposure Level (mg kg⁻¹ bw day⁻¹)

AOEL - Acceptable Operator Exposure Level - Systemic (mg kg⁻¹ bw day⁻¹)

0.04

Dermal penetration studies (%)

2.5-13

concentration dependent

Dangerous Substances Directive 76/464

Exposure Routes

Public

No unacceptable risks to bystanders identified with proposed uses

Occupational

No unacceptable risks to operators or other workers identified for poposed uses

Mammalian dose elimination route and rate

Rapidly metabolised and excreted via faeces and urine

Health issues

Specific human health issues

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

Reproduction / development effects

Acetyl cholinesterase inhibitor

Neurotoxicant

Respiratory tract irritant

Skin irritant

Skin sensitiser

No data found

Eye irritant

Phototoxicant

No data found

General human health issues

Possible liver toxicant
Possible blood toxicant
Endocrine issues - Estrogenic effect

Handling issues

Property

Value and interpretation

General

Not explosive or oxidising
IMDG Transport Hazard Class 9
Not expected to auto-ignite; Not highly flammable

CLP classification 2013

Environment: H400, H410

WHO Classification

U (Unlikely to present an acute hazard)

UN Number

UN3077

Waste disposal & packaging

Packaging Group III (minor danger)

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

pyriproxyfen

French

pyriproxyfen

German

Pyriproxyfen

Danish

pyriproxyfen

Italian

piriproxifen

Spanish

piriproxifen

Greek

Polish

pyriproksyfen

Swedish

pyriproxyfen

Hungarian

piriproxifen

Dutch

pyriproxyfen

Norwegian

Record last updated:	04/09/2025
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