Chemicals / Complex Chemical Agents/ Chemical:

Cephalexin (with special reference to Hedgehogs, Lagomorphs, Ferrets, Great Apes and Cranes)




Information in this page has been entered to support the current volumes of Wildpro and further information will be added as new volumes are completed. This page is not intended to substitute for the manufacturer's data sheet and the information is not yet complete for all species, or for all contra-indications etc.

CAUTION: Before any pharmaceutical product is used, the manufacturer's data sheet, containing information on uses, dosage and administration, contra-indications, warnings etc., should always be consulted. It is important to remember that licensing of pharmaceutical products for use in a particular species/condition, as well as mandatory meat and milk withdrawal times for food-producing animals, varies between countries and changes with time. Withdrawal times also may vary between different pharmaceutical formulations and depending on route of administration. In the EU, the prescription cascade must be followed (see LCofC1.2H and W564.Apr05.w1); note that specific restrictions apply for food-producing animals. In the USA, FARAD may be consulted regarding residues and meat and milk withdrawal times.

General Chemical Information

A bactericidal antibiotic in the cephalosporin group. (B263)

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Names and Formulae
Type First-generation cephalosporin antibiotic. (B263)
Alternative Names
  • Cefalexin. (B546)
  • "Cefanex; C-Lexin; Keflet; Keflex; Keftab; 7-(D-alpha-amino-alpha-phenylacetamido)-3-methyl-3-cephem-4-carboxylic acid monohydrate; Cefalexin; Ibilex." (W324)
Chemical Formula C16H17N3O4S (W324)
Chemical Structure --
Molecular Weight 347.388. (W324)
Related Chemicals --

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Physical Properties / Chemistry
  • Cephalexin monohydrate: white to off-white crystalline powder. (B263)

Melting point --
Boiling point --
Density --
Water solubility
  • Slightly soluble. (B263)
Other solubility
  • Practically insoluble in alcohol. (B263)
Acid/Base --

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Pharmacology & General Information
Pharmacology Inhibits mucopeptide synthesis in bacterial cell walls. This results in a defective cell wall and an osmotically unstable spheroplast. (B263)
Storage / Stability
  • Tablets, capsules, powder for oral suspension: store in tight containers at room temperature (15-30C). (B263)
  • Reconstituted oral suspension: stable for two weeks. (B263)
Legal Category (In UK) --

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Associated Techniques




(Further Reading)
Click image for full contents list of ELECTRONIC LIBRARY

Authors Debra Bourne (V.w5)
Referees Suzanne I. Boardman (V.w6); Becki Lawson (V.w26)

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Therapeutic Information

  • Generally very good against Gram-positive bacteria. (B263)
  • Variable to poor activity against Gram-negative bacteria. (B263)
  • Good activity in vitro against group A beta-haemolytic, group B Streptococcus spp., non-enterococcal group D Streptococci (Streptococcus bovis), Staphylococcus intermedius, Staphylococcus aureus, Proteus mirabilis. (B263)
  • Very active against some strains of Escherichia coli, Klebsiella spp., Actinobacillus spp., Pasteurella spp., Haemophilus equigenitalis, Shigella spp. and Salmonella spp.  (B263)
  • Most anaerobes are susceptible (not Bacteroides fragilis).  (B263)
  • Against most Corynebacterium spp. (not Corynebacterium (Rhodococcus) equi.). (B263)
Appropriate Use --
Limitations Generally not useful against:

Oral cephalexins may not be useful against Staphylococcus epidermidis. (B263)

Notes --

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Pharmacokinetics and Drug Interactions
Oral Absorption / Bioavailability
  • In humans: rapid and complete absorption following conversion from base to HCl (hydrochloride) form. (B263)
  • Absorption is not much affected by the presence of food. (B263)
  • In dogs: bioavailability following oral administration about 75%; mean oral dose of 12.7mg/kg resulted in peak serum levels of 18.6 g/ml after about 1.8 hours. (B263)
  • In cats: bioavailability following oral administration about 75%; mean oral dose of 22.9mg/kg resulted in peak serum levels of 18.7 g/ml after about 2.6 hours. (B263)
  • In calves: bioavailability following intramuscular injection of the sodium salt of cephalexin (Ceporex injection - Glaxovet) of 74%. (B263)
  • Widely distributed to most tissues and fluids, including in bone (increased levels in inflamed bone), pleural fluid, pericardial fluid, synovial fluid. (B263)
  • High levels in urine and may reach therapeutic concentrations in bile if no biliary obstruction. (B263)
  • Poor penetration into the prostate and into the aqueous humour of the eye. (B263)
  • Does not reach therapeutically effective levels in the cerebrospinal fluid even when the meninges are inflamed. (B263)
  • Low concentrations reached in milk. (B263)
  • Fetal serum levels may reach or pass 10% of maternal serum levels. (B263)
Plasma Protein binding / Storage
  • Wide, species-specific variation in plasma protein binding. (B263)
    • Less binding to equine and canine plasma proteins than to human plasma proteins. (B263)
Elimination Route
  • Excretion of cephalosporins is via the kidneys; tubular secretion and/or glomerular filtration. (B263)
Elimination half-life / Clearance Rate
  • Dogs: elimination half-life one to two hours. (B263)
  • Cats: elimination half-life one to two hours. (B263)
  • Calves: serum half-life about 90 minutes following intramuscular injection of the sodium salt of cephalexin (Ceporex injection - Glaxovet). (B263)
Drug Interactions
  • Potential additive nephrotoxicity if cephalosporins are used concurrently with parenteral aminoglycosides or other nephrotoxic drugs. (B263)
  • Synergistic or additive activity may occur when used concurrently with aminoglycosides, penicillins or chloramphenicol, against certain bacteria. (B263)
  • Use concurrently with bacteriostatic antibiotics is not generally recommended, particularly in acute infections with rapidly-proliferating bacteria. (B263)
  • Serum levels and serum half lives are increased by administration of probenecid as this blocks the tubular secretion by the kidneys of most cephalosporins. (B263)

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Formulations available
  • Oral: tablets, capsules and powder for reconstitution. (B263)
  • Injectable: sodium salt (Ceporex injection - Glaxovet) for intramuscular or subcutaneous use. (B263)


Doses / Administration Routes / Frequencies

Use of Drugs (Medication):

  • Before administration of any pharmaceutical product the manufacturer's datasheet must be consulted regarding operator safety, relevant withdrawal times etc.
  • Many drugs are not registered for use in particular species and additional care should be taken in their use, with proper regard for possible toxic effects. 
  • Consideration should be given to relevant legislation regarding the use of drugs.
  • In the UK, guidelines regarding the use of drugs are set out in the Royal College of Veterinary Surgeons' Guide to Professional Conduct 2000: (See: LCofC1 - RCVS Guide to Professional Conduct 2000 - Choice of Medicinal Products).

Erinaceus europaeus - West European Hedgehog:

  • 30 mg/kg orally or subcutaneously. Broad-spectrum bactericidal; especially useful for skin and soft tissue infections, particularly in cases of pyoderma, abscessation and infected wounds. (B284.6.w6)
  • 36 mg/kg once daily subcutaneously. (D107)

Lagomorphs - Oryctolagus cuniculus domesticus - Domestic rabbit:

  • 15 mg/kg subcutaneously twice daily. (B373.Guide.w41, B548.w8, B600.4.w4)
  • 11 - 22 mg/kg orally every eight hours. (B548.w8, B602.41.w41)
  • 20 mg/kg subcutaneously once daily. (B600.4.w4)
  • 15 - 30 mg/kg subcutaneously every 24 hours. (B603.5.w5)
  • 15 mg/kg orally every 12 hours. (B603.5.w5)
  • 15 - 20 mg/kg subcutaneously every 12 - 24 hours. (B546, B601.15.w15)
  • "Do not give orally." (B601.15.w15)

Ferrets - Mustela putorius furo - Ferret:

  • 15 - 25 mg/kg orally twice daily. "Good for urinary and respiratory infections." (B626.App.w22)
  • 15 - 30 mg/kg orally every 8 - 12 hours. (B602.41.w41, B631.21.w21)
  • 15 - 25 mg/kg orally twice or three times daily. Note: can potentiate aminoglycoside toxicity. (J213.3.w1)

Great Apes

  • Adult Pan troglodytes - Chimpanzee: 1 - 4 grams total dose, twice daily or three times daily. (W768.Jun2012.w1)
  • Primates: 25-40 mg/kg orally twice daily. Broad spectrum against Gram-positive organisms. Used in the treatment of respiratory, skin and urinary tract infections. (D425.3.15.w3o)


  • 35-50 mg/kg orally every six hours. (B12.56.w14, B115.8.w4, B336.20.w20)
    • Broad spectrum, useful against most Gram-positive organisms and some Gram-negative organisms, including a variety of enteric organisms. (B12.56.w14, B115.8.w4)
Monitoring parameters
  • For efficacy. (B263)
  • Intensified renal monitoring may be required in patients with diminished renal function. (B263)

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Withdrawal period / Withholding time
Notes Before the use of any pharmaceutical product in food-producing animals the label instructions for the product should be consulted regarding withdrawal requirements.

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Toxic Information

Toxic effects of Pharmaceutical Products
Contraindications / Precautions
  • Contraindicated in patients with a known hypersensitivity to cephalosporins. (B263)
  • Must be used with caution in patients with documented hypersensitivity to other beta-lactam antibiotics such as penicillins; in humans up to15% (estimated) of patients hypersensitive to penicillins will be sensitive to cephalosporins. (B263)
  • In pregnancy use only if potential benefits outweigh the risks, as cephalosporins cross the placenta and safe use of cephalosporins during pregnancy has not been firmly established. (B263)
  • Oral dosing is not recommended in patients with septicaemia, shock or other severe illness in which the absorption of drugs from the gastrointestinal tract may be significantly delayed or diminished. (B263)
  • Dose may need to be reduced in patients with renal failure. (B263)
Adverse Effects / Side Effects / Warnings Relatively low frequency of occurrence and generally not serious. (B263)
  • Hypersensitivity reactions:
    • Unrelated to dose. (B263)
    • May result in rash, fever, eosinophilia, neutropaenia, agranulocytosis, thrombocytopaenia, leucopaenia, anaemias, lymphadenopathy.
    • Interstitial nephritis has been reported as a hypersensitivity reaction with cephalexin and some other cephalosporins.
    • May cause full-blown anaphylaxis. (B263)
  • In dogs: salivation, tachypnoea and excitement have been reported. (B263)
  • In cats: emesis and fever have been reported. (B263)
  • Nephrotoxicity is rare with normal doses in patients with normal renal function, but susceptibility may be increased in patients with renal dysfunction, geriatric patients, or patients receiving other nephrotoxic drugs. (B263)
  • Gastrointestinal side effects such as anorexia, vomiting and diarrhoea may occur; these may be reduced by administration together with a small meal. (B263)
  • Antibiotic-associated diarrhoea may occur due to altered gut flora. (B263)
  • In the colon, resistant bacteria may maintain residence, being selected out. (B263)
  • Pain may occur at the injection site when cephalosporins are given intramuscularly. (B263)
Operator Warnings Before the use of any pharmaceutical product the label instructions for the product should be consulted regarding operator safety/warnings.
Overdose / Acute Toxicity
  • Gastro-intestinal effects are the most likely to be seen. (B263)
  • High dose or very prolonged use has been associated with tubular necrosis and with neurotoxicity, also (with an immunological component) neutropaenia, agranulocytosis, thrombocytopaenia, hepatitis, positive Coomb's test and interstitial nephritis. (B263)

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Detailed Toxicological Information
Classification --
Acute Toxicity --
Chronic Toxicity --
Reproductive effects --
Teratogenic effects
  • No documented teratogenic effects from use during pregnancy. (B263)
Mutagenic effects --
Carcinogenic effects


Organ toxicity --
Bird Toxicity --
Aquatic organism activity --
Other organism toxicity --

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Nutrient Information

Nutritional Data
Sources --
Biological Use --
Recommended Daily Allowance / Recommended level in food --
Stability in food (Storage time) --
Interactions --

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External / Environmental Information

External / Environmental Uses
Use --
Formulation --
Application method --
Application Concentration --
Persistence of Effect / Frequency of Application --

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Effects on the Environment
Effects in the aquatic environment


Effects on land --

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Persistence in the Environment
Breakdown in soil and groundwater


Breakdown in water --
Breakdown in vegetation --

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