Eprinomectin

Eprinomectin	Last updated: 15/09/2025
(Also known as: MK 397)

GENERAL INFORMATION

Description

A semi-synthetic compound of the avermectin family, intended for the treatment of internal and external parasites

Examples of veterinary uses

Used for treatment and control of gastrointestinal roundworms, lungworms, warbles, sucking and biting lice, chorioptic and sarcoptic mange mites in beef and dairy cattle

Examples of species treated

Cattle; Sheep; Goats; Cats; Deer

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

Eprinomectin exhibits isomerism as a mixture of two closely related compounds: component B1a and component B1b which are stereoisomers. Component B1a has the formula C₅₀H₇₅NO₁₄, while B1b is C₄₉H₇₃NO₁₄, differing slightly in their side chains and stereochemistry.

Chemical formula

C₅₀H₇₅NO₁₄+C₄₉H₇₃NO₁₄

Canonical SMILES

CCC(C)C1C(C=CC2(O1)CC3CC(O2)CC=C(C(C(C=CC=C4COC5C4(C(C=C(C5O)C)C(=O)O3)O)C)OC6CC(C(C(O6)C)OC7CC(C(C(O7)C)NC(=O)C)OC)OC)C)C

Isomeric SMILES

CC[C@H](C)[C@@H]1[C@H](C=C[C@@]2(O1)C[C@@H]3C[C@H](O2)C/C=C(/[C@H]([C@H](/C=C/C=C/4\CO[C@H]5[C@@]4([C@@H](C=C([C@H]5O)C)C(=O)O3)O)C)O[C@H]6C[C@@H]([C@H]([C@@H](O6)C)O[C@H]7C[C@@H]([C@@H]([C@@H](O7)C)NC(=O)C)OC)OC)\C)C

International Chemical Identifier key (InChIKey)

ZKWQQXZUCOBISE-CRTGXIDZSA-N

International Chemical Identifier (InChI)

InChI=1S/C49H73NO14/c1-25(2)43-28(5)17-18-48(64-43)23-35-20-34(63-48)16-15-27(4)44(26(3)13-12-14-33-24-57-46-42(52)29(6)19-36(47(53)60-35)49(33,46)54)61-40-22-38(56-11)45(31(8)59-40)62-39-21-37(55-10)41(30(7)58-39)50-32(9)51/h12-15,17-19,25-26,28,30-31,34-46,52,54H,16,20-24H2,1-11H3,(H,50,51)/b13-12-,27-15-,33-14-/t26-,28-,30-,31-,34+,35-,36-,37+,38-,39-,40-,41+,42+,43+,44-,45+,46+,48+,49+/m0/s1

2D structure diagram/image available?

Yes

General status

Veterinary substance type

Insecticide, Acaricide, Antiparasitic, Nematicide, Anthelminthic, Endectocide

Substance groups

Avermectin

Minimum active substance purity

Known relevant impurities

Substance origin

Semi-synthetic

Mode of action

Contact and stomach action with limited systemic activity, blocks electrical activity in nerves and muscles of pest. Glutamate-gated chloride channel (GluCl) allosteric modulator.

Molecular targets

[Glutamate-gated chloride channel (GluCl), Modulator]

CAS RN

123997-26-2

EC number

CIPAC number

US EPA chemical code

PubChem CID

Therapeutic Class

Antiparasitic products, insecticides & repellents: Endectocides

ATCvet Code

QP54AA04

Controlled Drug?

Regulation 37/2010 MRL Classification

Allowed substance (Table 1: Bovine)

Molecular mass

900.11

PIN (Preferred Identification Name)

IUPAC name

mix of (10E,14E,16E)-(1R,4S,5'S,6S,6'R,8R,12S,13S,20R,21R,24S)-6'-[(S)-sec-butyl]-21,24-dihydroxy-5',11,13,22-tetramethyl-2-oxo-(3,7,19-trioxatetracyclo[15.6.1.14,8.020,24]pentacosa-10,14,16,22-tetraene)-6-spiro-2'-(5',6'-dihydro-2'H-pyran)-12-yl 4-O-(4-acetamido-2,4,6-trideoxy-3-O-methyl-a-L-lyxo-hexopyranosyl)-2,6-dideoxy-3-O-methyl-a-L-arabino-hexopyranoside (major component) and (10E,14E,16E)-(1R,4S,5'S,6S,6'R,8R,12S,13S,20R,21R,24S)-21,24-dihydroxy-6'-isopropyl-5',11,13,22-tetramethyl-2-oxo-(3,7,19-trioxatetracyclo[15.6.1.14,8.020,24]pentacosa-10,14,16,22-tetraene)-6-spiro-2'-(5',6'-dihydro-2'H-pyran)-12-yl 4-O-(4-acetamido-2,4,6-trideoxy-3-O-methyl-a-L-lyxo-hexopyranosyl)-2,6-dideoxy-3-O-methyl-a-L-arabino-hexopyranoside (minor component)

CAS name

(4'R)-4'-(acetylamino)-4'-deoxyavermectin B1

Forever chemical

Other status information

Relevant Environmental Water Quality Standards

Physical state

White or pale yellow crystalline powder

Commercial

Property

Value

Availability status

Current

Introduction & key dates

1997, first approvals USA

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

Bimeda Animal Health Ltd
Boehringer Ingelheim Vetmedica GmbH
Ceva Animal Health Ltd

Example products using this active

Eprine
Bimeprine Pour-on Solution
Broadline Spot-on Solution
Epricert Pour-on Solution

Formulation and application details

Available in a variety of formulations including solutions for injection and topically applied products such as spot-ons and pour-ons

Commercial production

Eprinomectin is produced through a semi-synthetic process that begins with fermentation of Streptomyces avermitilis, a soil-dwelling bacterium that naturally produces avermectins. These compounds are then chemically modified to enhance their pharmacological properties and reduce toxicity. Specifically, eprinomectin is derived from avermectin B1 by introducing an epoxide group and modifying the sugar moiety to improve lipophilicity and systemic absorption. The synthesis involves multiple steps of purification, esterification, and oxidation under controlled conditions to ensure high purity and potency.

Impact on climate of production and use

As microbial-based products tend to use fermentation-based production processes rather than chemical synthesis, they typically have a lower fossil fuel input in formulation and active ingredient creation, and also have reduced downstream emissions due to biodegradability and minimal soil disruption, their life-cycle GHG emissions are expected to be low. Whilst hard and precise data is not available, broad estimates suggest that typically emissions are likely to be below 5 kg CO₂e/kg. However, the semi-synthetic nature of the production process for this substance is likely to increase emissions.

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

3.5

Low

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

Melting point (°C)

164

Boiling point (°C)

Degradation point (°C)

Flashpoint (°C)

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

2.51 X 10⁰⁵

Calculated

Log P

5.4

High

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

1.23

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

May be introduced into the environment via the faeces and urine of teated animals

Degradation

Property

Value

Source; quality score; and other information

Interpretation

Soil degradation (days) (aerobic)

DT₅₀ (typical)

Moderately persistent

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)

3000

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

0.94

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

24a-hydroxymethyl eprinomectin

Rat (Faeces)

24a-hydoxy eprinomectin

Rat (Faeces)

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

Rat

High

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)

272

Colinus virginianus

Moderate

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)

Moderate

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)

1.2

Oncorhynchus mykiss

Moderate

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

0.37

Oncorhynchus mykiss 96 hr

Moderate

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

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

0.00045

Daphnia magna

High

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) (14 day NOEC)

7.0

Raphidocelis subcapitata

Low

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)

Rat

High

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)

0.005

Dog SF=200

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

In cattle eprinomectin is mainly excreted in bile and faeces, only a small proportion is excreted in urine or is present in milk.

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

Possible liver and kidney toxicant

Handling issues

Property

Value and interpretation

General

IMDG Transport Hazard Code 6.1

CLP classification 2013

WHO Classification

Not listed (Not listed)

UN Number

UN2811

Waste disposal & packaging

Packaging group II (moderate danger)

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

eprinomectin

French

eprinomectine

German

Eprinomectine

Danish

Italian

Spanish

eprinomectina

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