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This information is provided by Provet for educational purposes only.

You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

Some antibiotics are contraindicated under certain circumstances

The following is a list of commonly used antibiotics and their contraindications :

Antibiotic Contraindications
  • Aminoglycosides - all unless otherwise indicated
  • Cats
  • Myasthenia gravis
  • Renal failure (care needed)
  • Pregnancy (gentamicin)
  • Use with other drugs (gentamicin)
  • Urinary obstruction (neomycin)
  • Amoxicillin (with or without clavulanic acid)
  • Ampicillin
  • Penicillin G (Benzylpenicillin)
  • Penicillin V (Phenoxymethylpenicillin)
  • Procaine Penicillin (Procaine Benzylpenicillin)
  • Benzylpenicillin (both Benzathine and Procaine)
  • Flucloxacillin
  • Pivampicillin
  • Ticarcillin (with clavulanic acid)


  • Not to be administered intrathecally
  • Animals with penicillin or cephalosporin sensitivity
  • Not to be used in gerbils, guinea pigs, hamsters or rabbits
  • Amoxicillin - not to be given to calves with rumen function
  • Cephalosporins - all unless otherwise indicated
  • Animals with cephalosporin or penicillin sensitivity
  • Chloramphenicols
  • Impaired liver function
  • Care in cats
  • Entire bulls (Florfenicol)
  • Macrolides and Lincosamides 
  • Clindamycin or lincomycin hypersentive animals
  • Not to be used in chinchillas,  guinea pigs, hamsters, horses, rabbits, other rodents,  ruminants, 
  • Intravenous injections in horses and goats (Tilmicosin)
  • Should not be used in pig feeds containing bentonite (Tilmicosin)
  • Nitroimidazoles
  • Small birds (mitronidazole)
  • Quinolones
  • Dogs under 8 months (Difloxacin)
  • Dogs under 12 months (Enrofloxacin and Marbofloxacin))
  • Cats under 8 weeks (Enrofloxacin)
  • Cats under 16 weeks (Marbofloxacin)
  • Sulphonamides - all (including potentiated) unless otherwise stated
  • Impaired kidney function
  • Impaired liver function
  • Animals with sulphonamide sensitivity
  • Animals with haematological disorders
  • Horses with drug-induced cardiac arrhythmia (Sulfadiazine with trimethoprim)
  • Dogs with keratitis sicca (Sulfadiazine with trimethoprim)
  • Oral use in calves with  a functional rumen (Sulfadiazine with trimethoprim)
  • NB Do not crush tablets for use in cats
  • Tetracyclines - all
  • Animals with impaired renal function (except for Doxycycline)
  • Last trimester of pregnancy
  • Neonates 
  • Oral use in ruminants
  • Patients with dysphagia
  • Patients with vomiting
  • Intravenous injection in dogs (some forms of oxytetracycline only)
  • Subcutaneous injection (in horses only)