Prazosin hydrochloride

Prazosin hydrochloride	Last updated: 20/10/2025
(Also known as: furazosin hydrochloride; prazosine hydrochloride; prazosina hydrochloride; prazosin HCl)

GENERAL INFORMATION

Description

A veterinary drug with multiple applications in animal health

Examples of veterinary uses

Used to manage high blood pressure, relax the urinary sphincter tone and allow easier urination. It may also be used as a treatment for congestive heart failure, systemic hypertension, or pulmonary hypertension.

Examples of species treated

Dogs, Cats

Approval status

VMR 2013/2033 approval status (GB/UK)

Not approved

EU Regulatory approval status

Not approved

Chemical structure

Isomerism

None

Chemical formula

C₁₉H₂₂ClN₅O₄

Canonical SMILES

COC1=C(C=C2C(=C1)C(=NC(=N2)N3CCN(CC3)C(=O)C4=CC=CO4)N)OC.Cl

Isomeric SMILES

International Chemical Identifier key (InChIKey)

WFXFYZULCQKPIP-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C19H21N5O4.ClH/c1-26-15-10-12-13(11-16(15)27-2)21-19(22-17(12)20)24-7-5-23(6-8-24)18(25)14-4-3-9-28-14;/h3-4,9-11H,5-8H2,1-2H3,(H2,20,21,22);1H

2D structure diagram/image available?

Yes

General status

Veterinary substance type

Alpha-blocker

Substance groups

Quinazoline derivative; Piperazine drug

Minimum active substance purity

Known relevant impurities

Substance origin

Synthetic

Mode of action

Inhibits the postsynaptic alpha-1 adrenoceptors. This inhibition blocks the narrowing effect of catecholamines on the blood vessels thus improving blood flow

Molecular targets

[Alpha-1A adrenergic receptor, Antagonist], [Alpha-1B adrenergic receptor, Antagonist], [Alpha-1D adrenergic receptor, Antagonst], [Voltage-gated inwardly rectifying potassium channel KCNH2, Inhibitor], [Alpha-2A adrenergic receptor, Binder] [Alpha-2B adrenergic receptor, Binder]

CAS RN

19237-84-4

EC number

242-903-4

CIPAC number

US EPA chemical code

PubChem CID

68546

Therapeutic Class

Cardiovascular system: Alpha-adrenoreceptor antagonsts

ATCvet Code

QC02CA01

Controlled Drug?

Regulation 37/2010 MRL Classification

Molecular mass

419.9

PIN (Preferred Identification Name)

IUPAC name

[4-(4-amino-6,7-dimethoxyquinazolin-2-yl)piperazin-1-yl]-(furan-2-yl)methanone;hydrochloride

CAS name

Global Governance status: Listed (✓) under

UK Poisons List Order 1972	Rotterdam Convention	Montreal Protocol
XNo The Poisons List Order 1972	XNo Rotterdam Convention	XNo Montreal Protocol
Stockholm Convention	OSPAR	EU Water Framework Directive
XNo Stockholm Convention	XNo OSPAR	XNo EU Water Framework Directive

Relevant Environmental Water Quality Standards

Forever chemical

Other status information

Physical state

A white, crystalline substance

Related substances & organisms

prazosin

Commercial

Property

Value

Availability status

Current

Introduction & key dates

1974, first synthesised; 1980s, vet use adopted

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

Pfizer Animal Health

Example products using this active

Minipress

Formulation and application details

Usually formulated using the hydrochloride derivative for oral administation

Commercial production

The production of prazosin hydrochloride involves a multi-step synthesis that builds its complex quinazoline-piperazine-furan framework. It begins with the reaction of 2-amino-4,5-dimethoxybenzoic acid with sodium cyanate, forming 6,7-dimethoxyquinazoline-2,4-diol. This intermediate is then chlorinated to yield 2,4-dichloro-6,7-dimethoxyquinazoline, which undergoes selective amination with ammonia to produce 2-chloro-6,7-dimethoxyquinazolin-4-amine. The final coupling step involves reacting this compound with (furan-2-yl)(piperazin-1-yl)methanone, forming prazosin. To obtain the hydrochloride salt, prazosin is treated with hydrochloric acid.

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 at pH 7 (mg l⁻¹)

500

Moderate

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

100

DMSO

Melting point (°C)

285

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

Considered to be an emerging contaminant in water systems mainly due to improper disposal and pharmaceutical manufacturing waste

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)

> 2000

Rat

Low

Mammals - Short Term Oral NOAEL (mg kg⁻¹ bw d⁻¹)

Mammals - Long Term (Chronic) Oral NOAEL (mg kg⁻¹ bw d⁻¹)

Birds - Acute LD₅₀ (mg kg⁻¹)

Birds - Short term dietary LC₅₀ (mg kg⁻¹ bw d⁻¹)

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)

Beneficial insects (Butterflies)

Contact

Notes

Oral

Notes

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)

> 2000

Rat

Low

Mammals - Short Term Oral NOAEL (mg kg⁻¹ bw d⁻¹)

Mammals - Long Term (Chronic) Oral NOAEL (mg kg⁻¹ bw d⁻¹)

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

Metabolised in the liver and eliminated through biliary excretion.

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

Eye irritant

Phototoxicant

No data found

General human health issues

May cause gastrointestinal disturbances

Handling issues

Property

Value and interpretation

General

Not explosive
Incompatible with strong oxidising agents
May emit hazardous fumes if heated

CLP classification 2013

Health: H302, H315, H319, H335, H361

WHO Classification

UN Number

Not regulated

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

Store under ambient conditions.

TRANSLATIONS

Language

Name

English

prazosin hydrochloride

French

German

Danish

Italian

Spanish

Greek

Polish

Swedish

Hungarian

Dutch

Norwegian

Record last updated:	20/10/2025
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

Your use of this website and its various databases is subject to the terms detailed in the University of Hertfordshire’s copyright and IPR statement that can be found at https://www.herts.ac.uk/about-us/legal. In addition, your use of this website and its various databases is subject to the terms of this additional Copyright Statement and the database Conditions of use document. Unless explicitly stated otherwise, the content of this website and databases are owned and controlled by the University of Hertfordshire. Site content, including its selection and arrangement, is owned by the University of Hertfordshire and is protected by copyright and other laws. Except as otherwise expressly permitted under copyright law or within the database Conditions of Use document, the content of this site may not be copied, reproduced, republished, downloaded, posted, broadcast or transmitted in any way without first obtaining the University of Hertfordshire’s written permission. By using our databases the user is deemed to have agreed to comply with all of the terms and conditions as described above and within all relevant documentation.