Milbemycin oxime (Ref: CGA-179246)

Milbemycin oxime (Ref: CGA-179246)	Last updated: 09/09/2025
(Also known as: Milbemycin-A4-oxim )

GENERAL INFORMATION

Description

A broad-spectrum antiparasitic drug producted by the fermentation by Streptomyces hygroscopicus variant aureolacrimosus

Examples of veterinary uses

Used for the treatment of heartworms, mites, fleas, ticks and nematodes (roundworms, tapeworms, hookworms)

Examples of species treated

Dogs; Cats

Approval status

VMR 2013/2033 approval status (GB/UK)

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

EU Regulatory approval status

Approved

Chemical structure

Isomerism

Milbemycin oxime exhibits isomerism primarily through its oxime functional group and multiple chiral centres. The oxime moiety can exist in E/Z geometrical forms, depending on the spatial arrangement around the C=N bond. Additionally, the compound’s macrolide ring contains several stereocentres, giving rise to various stereoisomers, including enantiomers and diastereomers, which can influence its pharmacological properties. It’s commonly used as a mixture of A3 and A4 derivatives.

Chemical formula

C₆₃H₈₈N₂O₁₄

Canonical SMILES

CCC1C(CCC2(O1)CC3CC(O2)CC=C(CC(C=CC=C4COC5C4(C(C=C(C5=NO)C)C(=O)O3)O)C)C)C.CC1CCC2(CC3CC(O2)CC=C(CC(C=CC=C4COC5C4(C(C=C(C5=NO)C)C(=O)O3)O)C)C)OC1C

Isomeric SMILES

CC[C@@H]1[C@H](CC[C@@]2(O1)C[C@@H]3C[C@H](O2)C/C=C(/C[C@H](/C=C/C=C/4\CO[C@H]\5[C@@]4([C@@H](C=C(/C5=N/O)C)C(=O)O3)O)C)\C)C.C[C@H]1CC[C@]2(C[C@@H]3C[C@H](O2)C/C=C(/C[C@H](/C=C/C=C/4\CO[C@H]\5[C@@]4([C@@H](C=C(/C5=N/O)C)C(=O)O3)O)C)\C)O[C@@H]1C

International Chemical Identifier key (InChIKey)

CKVMAPHTVCTEMM-ALPQRHTBSA-N

International Chemical Identifier (InChI)

InChI=1S/C32H45NO7.C31H43NO7/c1-6-27-21(4)12-13-31(40-27)17-25-16-24(39-31)11-10-20(3)14-19(2)8-7-9-23-18-37-29-28(33-36)22(5)15-26(30(34)38-25)32(23,29)35;1-18-7-6-8-23-17-36-28-27(32-35)21(4)14-26(31(23,28)34)29(33)37-25-15-24(10-9-19(2)13-18)39-30(16-25)12-11-20(3)22(5)38-30/h7-10,15,19,21,24-27,29,35-36H,6,11-14,16-18H2,1-5H3;6-9,14,18,20,22,24-26,28,34-35H,10-13,15-17H2,1-5H3/b8-7+,20-10+,23-9+,33-28-;7-6+,19-9+,23-8+,32-27-/t19-,21-,24+,25-,26-,27+,29+,31+,32+;18-,20-,22+,24+,25-,26-,28+,30-,31+/m00/s1

2D structure diagram/image available?

Yes

General status

Veterinary substance type

Anthelmintic agent; Ectoparasiticide

Substance groups

Micro-organism derived substance

Minimum active substance purity

>95%

Known relevant impurities

Substance origin

Natural

Mode of action

Opens glutamate sensitive chloride channels in neurons and myocytes of invertebrates, leading to hyperpolarisation of these cells and blocking of signal transfer.

Molecular targets

[GABA, Agonist]

CAS RN

129496-10-2

EC number

CIPAC number

US EPA chemical code

PubChem CID

Therapeutic Class

Antiparasitic products, insecticides and repellents: Milbemycins

ATCvet Code

QP54AB01

Controlled Drug?

Regulation 37/2010 MRL Classification

Molecular mass

1097.4

PIN (Preferred Identification Name)

None

IUPAC name

mixture of 70% (10E,14E,16E)-(1R,4S,5'S,6R,6'R,8R,13R,20R,24S)-6'-ethyl-24-hydroxy-5',11,13,22-tetramethyl-(3,7,19-trioxatetracyclo[15.6.1.14,8.020,24]pentacosa-10,14,16,22-tetraene)-6-spiro-2'-(tetrahydropyran)-2,21-dione 21-(EZ)-oxime and 30% (10E,14E,16E)-(1R,4S,5'S,6R,6'R,8R,13R,20R,24S)-24-hydroxy-5',6',11,13,22-pentamethyl-(3,7,19-trioxatetracyclo(15.6.1.14,8.020,24)pentacosa-10,14,16,22-tetraene)-6-spiro-2'-(tetrahydropyran)-2,21-dione 21-(EZ)-oxime

CAS name

(6R,25R)-5-demethoxy-28-deoxy-6,28-epoxy-25-ethyl-5-(hydroxyimino)milbemycin B mixture with (6R,25R)-5-demethoxy-28-deoxy-6,28-epoxy-5-(hydroxyimino)-25-methylmilbemycin B

Forever chemical

Other status information

Relevant Environmental Water Quality Standards

Physical state

Crystalline solid

Commercial

Property

Value

Availability status

Current

Introduction & key dates

Circa 1972, introduced

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

Krda d.d. Novo Mesto
Novartis

Example products using this active

Aderexa Chewable Tablets
Mektix Chewable Tablets
Milbemax
Milprazon

Formulation and application details

Usually formulated as tablets for oral administration

Commercial production

The production of milbemycin oxime involves a two-step chemical synthesis starting from milbemycin. First, an oxidation reaction is carried out using oxidising agents like hypochlorite or chlorite, with piperidine nitrogen-oxygen free radicals and halides acting as catalysts. This reaction, conducted in dichloromethane at low temperatures, converts milbemycin into an intermediate known as milbemycin ketone. Next, the ketone undergoes an oximation reaction, where it is treated with hydroxylamine hydrochloride in a 1,4-dioxane solvent, resulting in the formation of milbemycin oxime.

Impact on climate of production and use

Milbemycin, itself, is a microbial-based compound produced via fermentation and will typically emit relatively low levels of GHGs during production. 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 conversion to the oxime will increase emissions levels, potentially significantly.

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)

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

Max @ 246nm

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)

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 dw soil)

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)

0.059

Cyprinus carpio

High

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)

> 100

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)

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)

200

Rat as product

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 5.0

Rat 4 hr

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

Metabolised in the liver; biliary excretion

Health issues

Specific human health issues (hazard-based)

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

Harmful by inhalation and ingestion

Handling issues

Property

Value and interpretation

General

Non-corrosive
Not expected to auto-ignite; Not highly flammable

CLP classification 2013

Health: H302, H332
Environment: H400, H410

WHO Classification

Not listed (Not listed)

UN Number

None allocated

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

milbemycin oxime

French

oxime de milbemycine

German

Danish

Italian

Spanish

Greek

Polish

Swedish

Hungarian

Dutch

Norwegian

Record last updated:	09/09/2025
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