Erythromycin

Erythromycin	Last updated: 12/09/2025
(Also known as: EES; abomacetin; abomacetin; erythromycin A)

GENERAL INFORMATION

Description

A macrolide antibiotic produced by Streptomyces erythreus and used in veterinary medicine

Examples of veterinary uses

Used to treat a range of bacterial infections including mastitis, pneumonia, tick-borne infections like Lyme Disease, sinus infections, wound infections, skin infections, bone infections, and certain other types of bacterial infections

Examples of species treated

Poultry; Cattle; Sheep; Pigs

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

Erythromycin exhibits stereoisomerism, primarily due to its complex macrolide structure, which includes multiple chiral centres and sugar moieties. The molecule contains a 14-membered lactone ring with several asymmetric carbon atoms, leading to the possibility of different stereoisomers that can influence its biological activity. Additionally, erythromycin can undergo epimerisation under acidic conditions, particularly at the C-6 position, which may reduce its antimicrobial efficacy and contribute to gastrointestinal side effects. Some derivatives and analogs of erythromycin, such as clarithromycin and azithromycin, are chemically modified to stabilise these stereocentres and improve pharmacokinetics. The optically active isomers of erythromycin have also been explored to separate desirable antibiotic effects from unwanted actions like cardiac side effects.

Chemical formula

C₃₇H₆₇NO₁₃

Canonical SMILES

CCC1C(C(C(C(=O)C(CC(C(C(C(C(C(=O)O1)C)OC2CC(C(C(O2)C)O)(C)OC)C)OC3C(C(CC(O3)C)N(C)C)O)(C)O)C)C)O)(C)O

Isomeric SMILES

CC[C@@H]1[C@@]([C@@H]([C@H](C(=O)[C@@H](C[C@@]([C@@H]([C@H]([C@@H]([C@H](C(=O)O1)C)O[C@@H]2C[C@@]([C@H]([C@@H](O2)C)O)(C)OC)C)O[C@H]3[C@@H]([C@H](C[C@H](O3)C)N(C)C)O)(C)O)C)C)O)(C)O

International Chemical Identifier key (InChIKey)

ULGZDMOVFRHVEP-UMCXFAKASA-N

International Chemical Identifier (InChI)

InChI=1S/C37H67NO13/c1-14-25-37(10,45)30(41)20(4)27(39)18(2)16-35(8,44)32(51-34-28(40)24(38(11)12)15-19(3)47-34)21(5)29(22(6)33(43)49-25)50-26-17-36(9,46-13)31(42)23(7)48-26/h18-26,28-32,34,40-42,44-45H,14-17H2,1-13H3/t18-,19+,20+,21+,22-,23+,24-,25-,26+,28+,29+,30-,31+,32-,34-,35-,36-,37-/m1/s1

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
erythromycin B trihydrate	Variant
erythromycin A dihydrate	Variant
erythromycin B dihydrate	Variant
erythromycin A	-

General status

Veterinary substance type

Antibiotic, Antibacterial, Antimicrobial, Medicinal drug

Substance groups

Macrolide

Minimum active substance purity

Known relevant impurities

FAO: N-demethyl-erythromycin A; anhydroerythromycin A; erythromycin A enol ether; pseudoerythromycin A enol ether, erythromycin E, erythromycin F

Substance origin

Natural

Mode of action

Inhibits protein synthesis which is the basis of this antimicrobial action

Molecular targets

[3S rRNA, Antagonist], [50S ribosomal protein L22, Antagonist], [50S ribosomal protein L4, Antagonist]

CAS RN

114-07-8

EC number

204-040-1

CIPAC number

US EPA chemical code

PubChem CID

Therapeutic Class

Antiinfectants for systemic use: Antibacterials for intramammary use

ATCvet Code

QJ51FA01

Controlled Drug?

Regulation 37/2010 MRL Classification

Allowed substance (Table 1: All food producing species)

Molecular mass

733.93

PIN (Preferred Identification Name)

IUPAC name

(3R,4S,5S,6R,7R,9R,11R,12R,13S,14R)-6-{[(2S,3R,4S,6R)-4-(dimethylamino)-3-hydroxy-6-methyloxan-2-yl]oxy}-14-ethyl-7,12,13-trihydroxy-4-{[(2R,4R,5S,6S)-5-hydroxy-4-methoxy-4,6-dimethyloxan-2-yl]oxy}-3,5,7,9,11,13-hexamethyl-1-oxacyclotetradecane-2,10-dione

CAS name

Forever chemical

Other status information

Relevant Environmental Water Quality Standards

Physical state

White to slightly yellow crystalline solid, slightly hygroscopic

Related substances & organisms

tulathromycin A

tilmicosin

Commercial

Property

Value

Availability status

Current

Introduction & key dates

1952, first isolated; 1953, patented; 1968, first reviewed; 1981, first total synthesis of erythromycin A

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

Ceva Animal Health Ltd
AdvaCare Pharma

Example products using this active

Erythrocin Soluble powder for Oral Solution
ErystinCare Tablets
Ery-tab
Ery-Ped

Formulation and application details

Available in enteric-coated tablets, slow-release capsules, oral suspensions, ophthalmic solutions, ointments, gels, and injections

Commercial production

Erythromycin is produced through a microbial fermentation process using the bacterium Saccharopolyspora erythraea. The production begins with inoculum development, where the bacterial strain is cultivated under controlled conditions to ensure high yield. This is followed by submerged fermentation, typically in large bioreactors, where the bacteria are fed a nutrient-rich medium containing sources of carbon, nitrogen, and essential minerals. During fermentation, the bacteria biosynthesize erythromycin as a secondary metabolite. Once fermentation is complete, the antibiotic is extracted from the broth using solvent extraction techniques, then purified. Advanced processes may also involve catalytic steps, such as using cytochrome P450 enzymes to optimize conversion of precursors into the final macrolide structure.

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.

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

2000

High

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

Melting point (°C)

135

resolidifies MP(2) = 190

Boiling point (°C)

Degradation point (°C)

Flashpoint (°C)

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

3.02 X 10⁰²

Calculated

Log P

2.48

Low

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

Dissociation constant pKa) at 25 °C

8.88

@ 25DegC

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

pH 6.3: 280nm

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)

Moderately persistent

DT₅₀ (lab at 20 °C)

DT₅₀ (field)

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

Note

USEPA data: >64 days in three soils - sandy clay loam, silty clay 7 silty loam

Manure DT₅₀ (days)

Temp and OM dependent data for sandy loam+cattle manure 20°C

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Note

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

Value

63.0

Moderately persistent

Note

at pH5 DT₅₀ 0.8 days; at pH9 DT₅₀ 35 days

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)

570

Notes and range

Estimated

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

2.25

Calculated

Transition state

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

des-N-methyl-erythromycin
Note: Major metabolite; Pharmacologically active

Humans (Liver)

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 4600

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)

349

Morone saxatilis

Low

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)

30.5

Daphnia magna

Moderate

Temperate Freshwater Aquatic invertebrates - Chronic 21 day NOEC (mg l⁻¹)

0.25

Daphnia magna

Moderate

Tropical Freshwater Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)

> 0.11

Ceriodaphnia dubia

Moderate

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) (LOEC)

> 1000

Lemna gibba

Low

Aquatic plants (rooted, growth rate, fresh) - 14 day (mg l⁻¹)

Algae - Acute (growth rate, fresh; mg l⁻¹) (EC₅₀)

0.02

Raphidocelis subcapitata

Moderate

Algae - Chronic (growth rate, fresh; mg l⁻¹) (NOEC)

0.01

Raphidocelis subcapitata

Moderate

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)

> 4600

Rat

Low

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

Mammals - Inhalation LC₅₀ (mg l⁻¹)

Other Mammal toxicity endpoints

Subcutaneous LD₅₀ = 427 mg kg⁻¹

Rat

Intravenous LD₅₀ = 426 mg kg⁻¹

Mouse

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

Largely (~95%) metabolised by the liver and excreted in the bile and to lesser extent the urine

Health issues

Specific human health issues

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

May cause diarrhoea, nausea, abdominal pain, and vomiting
Reported cases of hearing impairment
Kidney, liver and lungs toxicant

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

erythromycin

French

erythromycine

German

Danish

Italian

Spanish

eritromicina

Greek

Polish

Swedish

Hungarian

Dutch

Norwegian

Record last updated:	12/09/2025
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