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Cefalexin
Last updated: 12/01/2024
(Also known as: cephalexin; ceporexin-E; cephanasten; cophalexin; CEX)

GENERAL INFORMATION
Description
A broad spectrum antibiotic commonly used in veterinary medicine
Availability status
Current
Introduction & key dates
1967, introduced
Examples of veterinary uses
Used to treat bacterial infections of the skin, urinary tract, respiratory tract, bones and joints
Examples of species treated
Dogs; Cats; Cattle; Pigs; Sheep
Approval status
VMR 2013/2033 approval status (GB/UK)
Approved
EU Regulatory approval status
Approved
Chemical structure
Isomerism
-
Chemical formula
C₁₆H₁₇N₃O₄S
Canonical SMILES
CC1=C(N2C(C(C2=O)NC(=O)C(C3=CC=CC=C3)N)SC1)C(=O)O
Isomeric SMILES
CC1=C(N2[C@@H]([C@@H](C2=O)NC(=O)[C@@H](C3=CC=CC=C3)N)SC1)C(=O)O
International Chemical Identifier key (InChIKey)
ZAIPMKNFIOOWCQ-UEKVPHQBSA-N
International Chemical Identifier (InChI)
InChI=1S/C16H17N3O4S/c1-8-7-24-15-11(14(21)19(15)12(8)16(22)23)18-13(20)10(17)9-5-3-2-4-6-9/h2-6,10-11,15H,7,17H2,1H3,(H,18,20)(H,22,23)/t10-,11-,15-/m1/s1
2D structure diagram/image available?
Yes
Cambridge Crystallographic Data Centre diagrams
Common Name Relationship Link
Cephalexin hydrate -
General status
Veterinary substance type
Antibiotic, Medicinal drug, Antibacterial, Antimicrobial
Substance groups
Cephalosporin
Minimum active substance purity
-
Known relevant impurities
-
Substance origin
Semi-synthetic
Mode of action
Interferes with the bacteria's cell wall formation, causing it to rupture, and killing the bacteria.
Molecular targets
[Penicillin-binding protein 3, Antagonist], [Penicillin-binding protein 2a, Antagonist], [Penicillin-binding protein 1b, Antagonist], [Penicillin-binding protein 2B, Antagonist], [Penicillin-binding protein 1A, Antagonist]
CAS RN
15686-71-2
EC number
239-773-6
CIPAC number
-
US EPA chemical code
-
PubChem CID
27447
Therapeutic Class
Antiinfectants for systemic use: Antibacterials for intramammary use
ATCvet Code
QJ51DA01
Controlled Drug?
No
Regulation 37/2010 MRL Classification
Allowed substance (Table 1: Bovine)
Molecular mass
347.39
PIN (Preferred Identification Name)
-
IUPAC name
(6R,7R)-7-{[(2R)-2-amino-2-phenylacetyl]amino}- 3-methyl-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene- 2-carboxylic acid
CAS name
7-(D-2-amino-2-phenylacetamido)-3-methyl-delta(sup 3)-cephem-4-carboxylic acid
Other status information
-
Relevant Environmental Water Quality Standards
-
Physical state
White crystalline powder
Formulations
Property
Product
Manufacturer
Authorisation Route
Legal Class (GB/UK)
Example products (past and present) using this active
Cefabactin Tablets Le Vet Beheer B.V. GB National authorisation Prescription only medicine to be authorised by a veterinarian (POM-V)
Cephacare flavour 50 mg tablets for cats and dogs Eucphar NV GB National authorisation Prescription only medicine to be authorised by a veterinarian (POM-V)
Cephorium Film-coated Tablets TVM UK Animal Health Ltd UK National authorisation Prescription only medicine to be authorised by a veterinarian (POM-V)
Ceporex Suspension Injection Solution MSD Animal Health UK UK National authorisation Prescription only medicine to be authorised by a veterinarian (POM-V)
Formulation and application details
Usually formulated as standard tablets, film-coated and chewable tablets as well as powders and intramammary suspensions for injection
ENVIRONMENTAL FATE
Property
Value
Source; quality score; and other information
Interpretation
Solubility - In water at 20 °C (mg l⁻¹)
1790
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
High
Solubility - In organic solvents at 20 °C (mg l⁻¹)
- - -
Melting point (°C)
197
Q3 Q = Miscellaneous data from online sources
3 = Unverified data of known source
-
Boiling point (°C)
727
Q3 Q = Miscellaneous data from online sources
3 = Unverified data of known source
-
Degradation point (°C)
- - -
Flashpoint (°C)
394
Q3 Q = Miscellaneous data from online sources
3 = Unverified data of known source
-
Octanol-water partition coefficient at pH 7, 20 °C
P
4.47 X 1000 Calculated -
Log P
0.65
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
Low
Fat solubility of residues
Solubility
- - -
Data type
- - -
Density (g ml⁻¹)
- - -
Dissociation constant pKa) at 25 °C
5.2
L3 L = Pesticide manuals and hard copy reference books / other sources
3 = Unverified data of known source
-
pKa(2) = 7.3
Vapour pressure at 20 °C (mPa)
4.31 X 10-10
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
Low volatility
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
Max: 260nm = 7750
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
-
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)
- - -
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
Kd (mL g⁻¹)
- - -
Koc (mL g⁻¹)
-
Notes and range
-
Freundlich
Kf (mL g⁻¹)
- - -
Kfoc (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)
> 20000
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
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
- - -
- - -
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
- - -
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 - Acute 7 day EC₅₀, biomass (mg l⁻¹)
- - -
Algae - Acute 72 hour EC₅₀, growth (mg l⁻¹)
- - -
Algae - Chronic 96 hour NOEC, growth (mg l⁻¹)
- - -
Mesocosm study data
NOEAEC mg l⁻¹
- - -
NOEAEC mg l⁻¹
- - -
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)
> 20000
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
Rat
Low
Mammals - Dermal LD₅₀ (mg kg⁻¹ body weight)
- - -
Mammals - Inhalation LC₅₀ (mg l⁻¹)
- - -
Other Mammal toxicity endpoints
Intraperitoneal LD₅₀ = 4000 mg kg⁻¹
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
Rat
-
Subcutaneous LD₅₀ > 6100 mg kg⁻¹
V3 V = ChemID Online Databases; Chemspider; PubChem. (ChemID )
3 = Unverified data of known source
Rat
-
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 (~80-90%) is excreted unchanged in urine within 6 hours of administration, remainder lost in bile and faeces
Q3 Q = Miscellaneous data from online sources
3 = Unverified data of known source
-
Health issues
Specific human health issues
Carcinogen
Genotoxic
Endocrine disruptor
No data found
A0 A = Chromosome aberration (EFSA database)
0 = No data
;
B0 B = DNA damage/repair (EFSA database)
0 = No data
;
C0 C = Gene mutation (EFSA database)
0 = No data
;
D0 D = Genome mutation (EFSA database)
0 = No data
;
E0 E = Unspecified genotoxicity type (miscellaneous data source)
0 = No data
No data found
Reproduction / development effects Acetyl cholinesterase inhibitor Neurotoxicant
Yes, known to cause a problem
No data found No data found
Respiratory tract irritant Skin irritant Skin sensitiser
Yes, known to cause a problem
Yes, known to cause a problem
No data found
Eye irritant Phototoxicant  
Yes, known to cause a problem
No data found  
General human health issues
May cause diarrhoea, dizziness, headache, indigestion, joint pain, stomach pain and tiredness
Handling issues
Property
Value and interpretation
General
Hazardous combustion or decomposition products are produced in a fire
CLP classification 2013
-
WHO Classification
Not listed (Not listed)
UN Number
-
Waste disposal & packaging
-
Shelf-life, storage, stability and reactivity
-
TRANSLATIONS
Language
Name
English
cefalexin
French
cefalexine
German
-
Danish
-
Italian
-
Spanish
cefalexina
Greek
-
Polish
-
Swedish
-
Hungarian
-
Dutch
-
Norwegian
-

Record last updated: 12/01/2024
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