Procaine benzylpenicillin

Procaine benzylpenicillin	Last updated: 16/09/2025
(Also known as: penicillin G procaine)

GENERAL INFORMATION

Description

A combination of benzylpenicillin with the local anaesthetic agent procaine used as an anesthetic

Examples of veterinary uses

Used as a local anaesthetic for minor surgical procedures on a variety of animals

Examples of species treated

Cattle; Sheep; Goats, Horses; Pigs; Dogs; Cats

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

Procaine benzylpenicillin exhibits chiral isomerism, due to the presence of multiple asymmetric carbon atoms in the benzylpenicillin portion of the molecule. The penicillin nucleus contains chiral centres at positions 3, 5, and 6, which are essential for its beta-lactam ring structure and antibacterial activity. The procaine component also contains a chiral centre, but in pharmaceutical formulations, procaine is typically used as a racemic mixture. When combined, procaine benzylpenicillin forms an equimolar salt, where the stereochemistry of benzylpenicillin governs the drug’s biological activity.

Chemical formula

C₂₉H₃₈N₄O₆S

Canonical SMILES

CCN(CC)CCOC(=O)C1=CC=C(C=C1)N.CC1(C(N2C(S1)C(C2=O)NC(=O)CC3=CC=CC=C3)C(=O)O)C

Isomeric SMILES

CCN(CC)CCOC(=O)C1=CC=C(C=C1)N.CC1([C@@H](N2[C@H](S1)[C@@H](C2=O)NC(=O)CC3=CC=CC=C3)C(=O)O)C

International Chemical Identifier key (InChIKey)

WHRVRSCEWKLAHX-LQDWTQKMSA-N

International Chemical Identifier (InChI)

InChI=1S/C16H18N2O4S.C13H20N2O2/c1-16(2)12(15(21)22)18-13(20)11(14(18)23-16)17-10(19)8-9-6-4-3-5-7-9;1-3-15(4-2)9-10-17-13(16)11-5-7-12(14)8-6-11/h3-7,11-12,14H,8H2,1-2H3,(H,17,19)(H,21,22);5-8H,3-4,9-10,14H2,1-2H3/t11-,12+,14-;/m1./s1

2D structure diagram/image available?

Yes

General status

Veterinary substance type

Anesthetic, Medicinal drug

Substance groups

Aminobenzoate

Minimum active substance purity

Known relevant impurities

Substance origin

Synthetic

Mode of action

Sodium channel modulator

Molecular targets

[Sodium channel protein type 10 subunit alpha, Antagonist], [Glutamate [NMDA] receptor subunit 3A, Antagonist], [5-hydroxytryptamine 3 receptor, Antagonist], [Sodium-dependent dopamine transporter, Antagonist], [Neuronal acetylcholine receptor subunit alpha-2, Antagonist]

CAS RN

54-35-3

EC number

CIPAC number

US EPA chemical code

PubChem CID

5903

Therapeutic Class

Nervous system: Anaesthetic

ATCvet Code

QN01BA52

Controlled Drug?

Regulation 37/2010 MRL Classification

Allowed susbstance (Table 1: All food producing species)

Molecular mass

570.7

PIN (Preferred Identification Name)

IUPAC name

2-(diethylamino)ethyl 4-aminobenzoate;(2S,5R,6R)-3,3-dimethyl-7-oxo-6-[(2-phenylacetyl)amino]-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid

CAS name

Forever chemical

Other status information

Relevant Environmental Water Quality Standards

Physical state

Related substances & organisms

procaine hydrochoride

Commercial

Property

Value

Availability status

Current

Introduction & key dates

1928, penicillin discovered; 1950s, procain salt developed; 1960s, widespread agricultural use

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

Bimeda Animal Health Ltd
MSD Animal Health UK Ltd
Norbrook Labortories Ltd

Example products using this active

Bimprocil Suspension for Injection
Depocillin Suspension for Injection
Nafpenzal Dry Cow
Ultrapen LA Suspension for Injection

Formulation and application details

Usually supplied as a sterile suspension solution for subcutaneous injection

Commercial production

The production of procaine benzylpenicillin involves combining two key components: benzylpenicillin and procaine. First, benzylpenicillin is produced through fermentation of Penicillium chrysogenum in a nutrient-rich medium under aerobic conditions. After fermentation, the penicillin is extracted using solvent partitioning, typically with amyl acetate or butyl acetate, and then purified through crystallization. Separately, procaine base is synthesised via chemical methods involving p-aminobenzoic acid and diethylaminoethanol. The two compounds are then reacted in equimolar amounts to form the procaine salt of benzylpenicillin.

Impact on climate of production and use

As microbial-based products tend to use fermentation-based production processes rather than chemical synthesis, they typically have a lower fossil fuel input in formulation and active ingredient creation, and also have reduced downstream emissions due to biodegradability and minimal soil disruption, their life-cycle GHG emissions are expected to be low. 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 semi-synthetic production process of procaine benzylpenicillin will push emissions higher.

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 metabolites

None

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

200

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)

High (class III)

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

200

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)

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

Majority is metabolised and the metabolised are rapidly (in minutes) excreted mostly in the urine

Health issues

Specific human health issues (hazard-based)

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

No data found

Reproduction / development effects

Acetyl cholinesterase inhibitor

Neurotoxicant

Respiratory tract irritant

Skin irritant

Skin sensitiser

No data found

Eye irritant

Phototoxicant

No data found

General human health issues

May cause cardiac and vasodilation effects
May cause serious allergic reactions
Harmful if swallowed

Handling issues

Property

Value and interpretation

General

When heated to decomposition it emits toxic fumes of nitroxides
IMDG Transport Hazard Class 6.1
Hygroscopic in air

CLP classification 2013

WHO Classification

Not listed (Not listed)

UN Number

UN2811

Waste disposal & packaging

Packaging Group III (minor danger)

Shelf-life, storage, stability and reactivity

TRANSLATIONS

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Name

English

procaine benzylpenicillin

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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