Xylazine

Xylazine	Last updated: 14/09/2025
(Not known by any other names)

GENERAL INFORMATION

Description

A thiazine derivative used in veterinary medicine for sedation

Examples of veterinary uses

Used to produce sedation and short periods of analgesia

Examples of species treated

Horses; Cattle; Elephants; Deer; Cats; Dogs; Sheep; Goats; Hedgehogs; Other farm and zoo animals

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

Xylazine, a structural analog of clonidine, exhibits isomerism primarily through its metabolites, which can form positional isomers depending on where functional groups like hydroxyl or oxo groups attach to the aromatic ring. These variations, such as 3-hydroxyxylazine versus 4-hydroxyxylazine, share the same molecular formula but differ in structure, affecting their biological activity and detection. Additionally, some derivatised forms of xylazine may show atropisomerism, where restricted rotation around a bond leads to stable stereoisomers.

Chemical formula

C₁₂H₁₆N₂S

Canonical SMILES

CC1=C(C(=CC=C1)C)NC2=NCCCS2

Isomeric SMILES

International Chemical Identifier key (InChIKey)

BPICBUSOMSTKRF-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C12H16N2S/c1-9-5-3-6-10(2)11(9)14-12-13-7-4-8-15-12/h3,5-6H,4,7-8H2,1-2H3,(H,13,14)

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
xylazine hydrochloride monohydrate	Variant hydrate

General status

Veterinary substance type

Sedative, Anesthestic, Analgesis, Muscle relaxant, Medicinal drug

Substance groups

Clonidine analoque

Minimum active substance purity

Known relevant impurities

Substance origin

Synthetic

Mode of action

Stimulates central α2-receptors. α2-adrenergic which decreases the release of norepinephrine and dopamine in the central nervous system causing the sedation

Molecular targets

[Alpha-2-adrenergic, Agonist]

CAS RN

7361-61-7

EC number

230-902-1

CIPAC number

US EPA chemical code

PubChem CID

5707

Therapeutic Class

Nervous system: Psycholeptics

ATCvet Code

QN05CM92

Controlled Drug?

Regulation 37/2010 MRL Classification

Allowed substance (Table 1: Bovine, Equidae)

Molecular mass

220.34

PIN (Preferred Identification Name)

N-(2,6-dimethylphenyl)-5,6-dihydro-4H-1,3-thiazin-2-amine

IUPAC name

N-(2,6-dimethylphenyl)-5,6-dihydro-4H-1,3-thiazin-2-amine

CAS name

Forever chemical

Other status information

Relevant Environmental Water Quality Standards

Physical state

Related substances & organisms

xylazine hydrochloride

Commercial

Property

Value

Availability status

Current

Introduction & key dates

1962, first synthesised

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

Chanelle Animal Health Ltd
Le Vet B.V.
Alfasan Nederland B.V.

Example products using this active

Chanazine Solution for Injection
Nerfasin Solution for Injection
Xylapan Solution for Injection

Formulation and application details

Usually supplied in solution for injection or as a powder to be prepared as a solution

Commercial production

Xylazine is synthesised through a multi-step chemical process that begins with the preparation of key intermediates such as 2,6-dimethylphenylisothiocyanate. This compound is typically formed by reacting N-(2,6-dimethylphenyl)acetamide with sodium hydride in an organic solvent like tetrahydrofuran, followed by treatment with carbon disulfide. The resulting isothiocyanate is then reacted with ethylenediamine to form the thiazine ring structure characteristic of xylazine. Further purification and conversion steps yield xylazine base, which can be transformed into xylazine hydrochloride through alkylation reactions using agents like methanesulfonic acid or alkyl bromides under controlled temperature and pH conditions.

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)

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)

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 soil and groundwater metabolites

None

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

1-amino-2,6-dimethylbenzene

2,6-xylidine

Cattle (Urine)

2-(4'-hydroxy-2',6'-di-methylphenylamino)-5,6-dihydro-4H-1,3-thiazine

Horses; Rats (liver)

2-(3'-hydroxy-2',6'-dimethylphenylamino)-5,6-dihydro-4H-1,3-thiazine

Horses; Rats (liver)

N-(2,6-dimethylphenyl)thiourea

Horses; Rats (liver)

2-(2',6'-dimethylphenylamino)-4-oxo-5,6-dihydro-1,3-thiazine

Horses; Rats (liver)

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 109

Mouse

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)

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)

> 109

Mouse

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

Extensive metabolism occurs with <1% unchanged being eliminated via urine in the first two hours after administration

Health issues

Specific human health issues (hazard-based)

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

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 toxicant
Adverse effects of xylazine in animals include muscle tremors, seizures and slowed heart rate
May cause vomiting

Handling issues

Property

Value and interpretation

General

No information available

CLP classification 2013

WHO Classification

Not listed (Not listed)

UN Number

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

xylazine

French

German

Danish

Italian

Spanish

Greek

Polish

Swedish

Hungarian

Dutch

Norwegian

Record last updated:	14/09/2025
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