Isoflurane

Isoflurane	Last updated: 15/09/2025
(Also known as: forane)

GENERAL INFORMATION

Description

A substance used for veterinary inhalational anesthesia

Examples of veterinary uses

Used in veterinary anaesthetic regimes for premedication, induction and analgesia

Examples of species treated

Elephants; Bears; Cats; Dogs; Horses; Fowls; Mammals; Reptiles; Caged birds; Rodents

Approval status

VMR 2013/2033 approval status (GB/UK)

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

EU Regulatory approval status

Approved

Chemical structure

Isomerism

Isoflurane exhibits structural isomerism, specifically positional isomerism. It shares its molecular formula with compounds like enflurane, but differs in the position of functional groups on the carbon chain. The clinical profiles of isoflurane and enflurane differ due to the spatial arrangement of atoms. Isoflurane does not possess chiral centres, so it does not exhibit optical isomerism.

Chemical formula

C₃H₂ClF₅O

Canonical SMILES

C(C(F)(F)F)(OC(F)F)Cl

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

PIWKPBJCKXDKJR-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C3H2ClF5O/c4-1(3(7,8)9)10-2(5)6/h1-2H

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
isoflurane	-

General status

Veterinary substance type

Anesthesetic

Substance groups

Halogenated ether

Minimum active substance purity

Known relevant impurities

Substance origin

Synthetic

Mode of action

Involves interactions with multiple receptor sites to interfere with synaptic transmission.

Molecular targets

[Gamma-aminobutyric-acid (GABA) receptor subunit alpha-1, Agonist], [Calcium-transporting ATPase type 2C member 1, Antagonist], [Glycine receptor subunit alpha-1, agonist], [Glutamate receptor 1, Antagonist], [Potassium voltage-gated channel subfamily A member 1, agonist], [ATP synthase delta chain, mitochondrial], [Calmodulin]

CAS RN

26675-46-7

EC number

247-897-7

CIPAC number

US EPA chemical code

PubChem CID

Therapeutic Class

Nervous system: Anaesthetics

ATCvet Code

QN01AB06

Controlled Drug?

Regulation 37/2010 MRL Classification

Allowed substance (Table 1: Equidae)

Molecular mass

184.49

PIN (Preferred Identification Name)

IUPAC name

2-chloro-2-(difluoromethoxy)-1,1,1-trifluoro-ethane

CAS name

Forever chemical

Other status information

Relevant Environmental Water Quality Standards

Physical state

Clear, colourless liquid

Commercial

Property

Value

Availability status

Current

Introduction & key dates

Circa 1975, first registrations

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

Piramal Critical Care Ltd
Zoetis UK Ltd
Virbac Ltd

Example products using this active

Isofane Inhalation Vapour Liquid
Isoflo inhalation vapour liquid

Formulation and application details

Usually supplied as a liquid from which vapours are inhaled

Commercial production

Isoflurane is produced through a multi-step halogenation process starting with 2,2,2-trifluoroethyl difluoromethyl ether as the base compound. This precursor undergoes exhaustive chlorination using chlorine gas, forming a mixture that includes unwanted byproducts like 1,1-dichloro-2,2,2-trifluoroethyl difluoromethyl ether. To selectively convert this mixture into isoflurane, the reaction is exposed to ultraviolet light in the presence of isopropanol, which helps reduce the undesired components and promote the formation of pure isoflurane. The process is carried out under controlled temperature and pressure conditions, often with Lewis acid catalysts like antimony pentachloride to enhance efficiency.

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)

4470

High

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

Melting point (°C)

Not applicable

Boiling point (°C)

48.5

Degradation point (°C)

Flashpoint (°C)

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

1.15 X 10⁰²

Calculated

Log P

2.06

Low

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

1.45

Dissociation constant pKa) at 25 °C

Vapour pressure at 20 °C (mPa)

31.7 X 10⁰⁶

Highly volatile. If applied directly to plants or soil, drift is a concern & mitigation is advisable

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

1.2990-1.3005

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)

> 4770

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)

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)

High (class III)

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 4770

Rat

Low

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

Mammals - Inhalation LC₅₀ (mg l⁻¹)

15.3

Rat 3 hr

Other Mammal toxicity endpoints

Intraperitoneal LD₅₀ = 4.28 mL kg⁻¹

Rat

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

Mainly eliminated via the lungs

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

Strong respiratory depressant
Muscle relaxant
May cause hypotension

Handling issues

Property

Value and interpretation

General

Not expected to auto-ignite; Not highly flammable

CLP classification 2013

WHO Classification

Not listed (Not listed)

UN Number

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

isoflurane

French

German

Danish

Italian

Spanish

isoflurano

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