Zilpaterol hydrochloride (Ref: RU 42173)

Zilpaterol hydrochloride (Ref: RU 42173)	Last updated: 16/09/2025
(Also known as: zilpaterol HCl; RU 41173)

GENERAL INFORMATION

Description

A synthetic beta2-adrenoreceptor agonist

Examples of veterinary uses

Used to improve growth and feeding efficiency

Examples of species treated

Cattle

Approval status

VMR 2013/2033 approval status (GB/UK)

Not approved

EU Regulatory approval status

Not approved

Chemical structure

Isomerism

Zilpaterol has two chiral carbons and consequently four optical enantiomers. Commercial product is usually a racemic trans-zilpaterol HCl, a mixture of the (6R,7R) and (6S,7S) enantiomers.

Chemical formula

C₁₄H₂₀ClN₃O₂

Canonical SMILES

CC(C)NC1CCN2C3=C(C1O)C=CC=C3NC2=O.Cl

Isomeric SMILES

CC(C)N[C@@H]1CCN2C3=C([C@H]1O)C=CC=C3NC2=O.Cl

International Chemical Identifier key (InChIKey)

GIEFXLLRTJNFGT-LOCPCMAASA-N

International Chemical Identifier (InChI)

InChI=1S/C14H19N3O2.ClH/c1-8(2)15-11-6-7-17-12-9(13(11)18)4-3-5-10(12)16-14(17)19;/h3-5,8,11,13,15,18H,6-7H2,1-2H3,(H,16,19);1H/t11-,13-;/m1./s1

2D structure diagram/image available?

Yes

General status

Veterinary substance type

Medicinal drug, Growth promotor

Substance groups

Beta-Adrenergic agonist

Minimum active substance purity

Known relevant impurities

Substance origin

Synthetic

Mode of action

A synthetic beta2-adrenoreceptor agonist that binds with the muscle beta-adrenoreceptors leading to the activation of protein kinase A, an enzyme responsible for changes in protein synthesis and degradation

Molecular targets

[Beta-2 adrenergic receptor, Agonist], [Beta-1 adrenergic receptor, Binder], [Muopiod receptor, Antagonist

CAS RN

119520-06-8

EC number

601-619-4

CIPAC number

US EPA chemical code

PubChem CID

11507658

Therapeutic Class

Growth promotor

ATCvet Code

None allocated

Controlled Drug?

Regulation 37/2010 MRL Classification

Molecular mass

297.78

PIN (Preferred Identification Name)

IUPAC name

(9R,10R)-9-hydroxy-10-(propan-2-ylamino)-1,3-diazatricyclo[6.4.1.04,13]trideca-4,6,8(13)-trien-2-one;hydrochloride

CAS name

Forever chemical

Other status information

Relevant Environmental Water Quality Standards

Physical state

White to yellow coloured powder

Commercial

Property

Value

Availability status

Current; Banned in some countries

Introduction & key dates

1980s, developed; 1990s, field trials; 2003, first approvals USA; 2013, voluntary market withdrawal

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

Intervet

Example products using this active

Zilmax

Formulation and application details

Usually formulated as a medicated feed additive or premix

Commercial production

The production of zilpaterol hydrochloride involves a multi-step chemical synthesis starting from a heterocyclic precursor such as 4,5,6,7-tetrahydroimidazo[4,5,1-jk][1]benzazepine-2,7-dione. The first step typically includes hydrogenation using a nickel-based or palladium catalyst to convert the oxime group at the 6-position into an amino group, forming a key intermediate. This is followed by alkylation, where the intermediate reacts with 2-bromopropane to introduce the isopropylamino side chain, yielding the active zilpaterol base. The compound is then subjected to reduction and purification, often under controlled temperature and pressure, to ensure high stereoselectivity and yield. Finally, the purified zilpaterol is reacted with hydrochloric acid to form the hydrochloride salt.

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)

150000

High

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

Melting point (°C)

200

Boiling point (°C)

Degradation point (°C)

Flashpoint (°C)

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

1.00 X 10⁰¹

Calculated

Log P

Low

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

Dissociation constant pKa) at 25 °C

8.09

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

Substance may enter the environment via the urine and faeces of treated animals or by leaching from spilt medicated feed.

Degradation

Property

Value

Source; quality score; and other information

Interpretation

Soil degradation (days) (aerobic)

DT₅₀ (typical)

DT₅₀ (lab at 20 °C)

21.5

Non-persistent

DT₅₀ (field)

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

Note

USEPA data: Soil DT₅₀ 17.3-24.8 days

Manure DT₅₀ (days)

Stable

No degradation seen in 126 days

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Stable

Note

pH sensitive: DT₅₀ 53 days at pH4, Dt50 28 days at pH9

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

Value

365

Very persistent

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)

566

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

1.66

Calculated

Low leachability

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)

> 500

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)

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)

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 500

Rat

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)

0.04

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

0.04

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

Eliminated almost completely via urine (50–55%) and faeces (40–42%) within 8 days

Health issues

Specific human health issues (hazard-based)

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

May cause cardiovasuclar effects
May cause tremors

Handling issues

Property

Value and interpretation

General

No information available

CLP classification 2013

Health: H302, H332, H372

WHO Classification

Not listed (Not listed)

UN Number

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

TRANSLATIONS

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Name

English

zilpaterol hydrochloride

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Swedish

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Record last updated:	16/09/2025
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