Bacitracin methylenedisalicylic acid

Bacitracin methylenedisalicylic acid	Last updated: 15/09/2025
(Also known as: bacitracin MD)

GENERAL INFORMATION

Description

A broad spectrum antibiotic used primarily against gram-positive infections often in combination with other antibacterial compounds such as tetracyclin or prednisolone

Examples of veterinary uses

Used to treart mastitis in lactating cows. Sometimes used as a growth promotor but now banned in many countries.

Examples of species treated

Meat poultry; Pigs; Sheep; Cattle; Rabbits

Approval status

VMR 2013/2033 approval status (GB/UK)

Not approved

EU Regulatory approval status

Not approved

Chemical structure

Isomerism

Bacitracin methylenedisalicylic acid exhibits complex stereoisomerism due to its structure as a cyclic polypeptide bound to a methylenedisalicylic acid moiety. The bacitracin portion contains multiple chiral centres arising from its diverse amino acid residues, including both L- and D-configurations. These stereocentres give rise to diastereomers. Additionally, the methylenedisalicylic acid component introduces geometric and positional isomerism, particularly in the orientation of the two salicylic acid rings connected via a methylene bridge. The isomeric complexity is further amplified by the possibility of epimerization at sensitive stereocentres during synthesis or storage, which can affect the compound’s antimicrobial potency and stability.

Chemical formula

C₈₁H₁₁₇N₁₇O₂₃S

Canonical SMILES

CCC(C)C(C1=NC(CS1)C(=O)NC(CC(C)C)C(=O)NC(CCC(=O)O)C(=O)NC(C(C)CC)C(=O)NC(CCCCN)C(=O)NC(CCCN)C(=O)NC(C(C)CC)C(=O)NC(CC2=CC=CC=C2)C(=O)NC(CC3=CN=CN3)C(=O)NC(CC(=O)O)C(=O)NC(CC(=O)N)C(=O)O)N.C1=CC=C(C(=C1)C(=O)OCOC(=O)C2=CC=CC=C2O)O

Isomeric SMILES

CC[C@H](C)[C@@H](C(=O)N[C@@H](CCCCN)C(=O)N[C@H](CCCN)C(=O)N[C@@H]([C@@H](C)CC)C(=O)N[C@H](CC1=CC=CC=C1)C(=O)N[C@@H](CC2=CN=CN2)C(=O)N[C@H](CC(=O)O)C(=O)N[C@@H](CC(=O)N)C(=O)O)NC(=O)[C@@H](CCC(=O)O)NC(=O)[C@H](CC(C)C)NC(=O)C3CSC(=N3)C(C(C)CC)N.C1=CC=C(C(=C1)C(=O)OCOC(=O)C2=CC=CC=C2O)O

International Chemical Identifier key (InChIKey)

POMORUSPLDFVEK-PHXAWWDYSA-N

International Chemical Identifier (InChI)

InChI=1S/C66H105N17O17S.C15H12O6/c1-9-35(6)52(70)65-81-48(32-101-65)62(96)76-43(26-34(4)5)58(92)74-42(22-23-50(85)86)57(91)83-53(36(7)10-2)63(97)75-40(20-15-16-24-67)55(89)73-41(21-17-25-68)56(90)82-54(37(8)11-3)64(98)79-44(27-38-18-13-12-14-19-38)59(93)77-45(28-39-31-71-33-72-39)60(94)78-46(30-51(87)88)61(95)80-47(66(99)100)29-49(69)84;16-12-7-3-1-5-10(12)14(18)20-9-21-15(19)11-6-2-4-8-13(11)17/h12-14,18-19,31,33-37,40-48,52-54H,9-11,15-17,20-30,32,67-68,70H2,1-8H3,(H2,69,84)(H,71,72)(H,73,89)(H,74,92)(H,75,97)(H,76,96)(H,77,93)(H,78,94)(H,79,98)(H,80,95)(H,82,90)(H,83,91)(H,85,86)(H,87,88)(H,99,100);1-8,16-17H,9H2/t35?,36-,37-,40-,41+,42+,43-,44+,45-,46+,47-,48?,52?,53-,54-;/m0./s1

2D structure diagram/image available?

Yes

General status

Veterinary substance type

Medicinal drug, Antibiotic, Antibacterial, Antimicrobial, Medicated feed additive

Substance groups

Polypeptide

Minimum active substance purity

Known relevant impurities

Substance origin

Natural

Mode of action

Inhibits the biosynthesis of bacterium cell wall

Molecular targets

[C55-isoprenyl pyrophosphate, Antagonist], [Insulin-degrading enzyme, Antagonist]; [Alpha-2-macroglobulin, Antagonist]

CAS RN

55852-84-1

EC number

259-862-3

CIPAC number

US EPA chemical code

PubChem CID

11980094

Therapeutic Class

Alimentary tract & metabolism: Intestinal anti-infective

ATCvet Code

QA07AA93

Controlled Drug?

Regulation 37/2010 MRL Classification

Allowed substance (Table 1: Bovine, Rabbit)

Molecular mass

1729.0

PIN (Preferred Identification Name)

IUPAC name

(4R)-5-[[(2S,3S)-1-[[(2S)-6-amino-1-[[(2R)-5-amino-1-[[(2S,3S)-1-[[(2R)-1-[[(2S)-1-[[(2R)-1-[[(1S)-3-amino-1-carboxy-3-oxopropyl]amino]-3-carboxy-1-oxopropan-2-yl]amino]-3-(1H-imidazol-5-yl)-1-oxopropan-2-yl]amino]-1-oxo-3-phenylpropan-2-yl]amino]-3-methyl-1-oxopentan-2-yl]amino]-1-oxopentan-2-yl]amino]-1-oxohexan-2-yl]amino]-3-methyl-1-oxopentan-2-yl]amino]-4-[[(2S)-2-[[2-(1-amino-2-methylbutyl)-4,5-dihydro-1,3-thiazole-4-carbonyl]amino]-4-methylpentanoyl]amino]-5-oxopentanoic acid;(2-hydroxybenzoyl)oxymethyl 2-hydroxybenzoate

CAS name

Forever chemical

Other status information

Banned in EU as growth promotor; Not approved as feed additive in EU

Relevant Environmental Water Quality Standards

Physical state

Related substances & organisms

bacitracin

bacitracin zinc

Commercial

Property

Value

Availability status

Considered obsolete but may be available in some countries

Introduction & key dates

1945, isolated

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

Lifecome Biochemistry Co. Ltd China
Yinuo Pharmchem

Example products using this active

Kemitracin 10
Fortracin
Md Bacitracin

Formulation and application details

Often sold as a premix or soluble powder

Commercial production

Bacitracin methylenedisalicylic acid is produced through a multi-step process that begins with leaching bacitracin from a premix using n-butanol as the extraction solvent. After soaking and filtering to remove microbial residues, the extract is concentrated at around 65 DegC. Separately, methylenedisalicylic acid is dissolved in n-butanol and added to the concentrated bacitracin solution to initiate complexation, typically for about 3 hours. The resulting complex is then subjected to acidic extraction using citric acid, followed by pH adjustment to 7.6 with sodium hydroxide to isolate the target compound in the aqueous phase. This solution is spray-dried to yield a crude product, which is then refined.

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

Released into the environment via the excretion of treated animals

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)

22.5

Soil & chicken manure at 20 °C for bacitracin

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

desamidobasitracin

Chickens; Pigs

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 3751

Mouse

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 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)

> 3751

Mouse

Low

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

Poisonous by intraperitoneal and intravenous routes

Mammalian dose elimination route and rate

Some metabolism, excreted in the urine and faeces within 24 hr

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 contact dermititis or skin sensitisation
May cause gastrointestinal problems
May cause delayed hypersensitivity

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

bacitracin methylenedisalicylic acid

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Danish

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Spanish

Greek

Polish

Swedish

Hungarian

Dutch

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Record last updated:	15/09/2025
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