VetSuite Veterinarians

Ciprofloxacin is a fluoroquinolone antibiotic and is related to enrofloxacin, marbofloxacin and orbofloxacin. Ciprofloxacin is one of the metabolites of enrofloxacin. It is well absorbed following oral administration, but its bioavailability is only half that of enrofloxacin when administered to dogs. Ciprofloxacin is most often used when bacterial sensitivity testing indicates it is potentially more effective than enrofloxacin.

Ciprofloxacin inhibits bacterial DNA gyrase, an enzyme that nicks and seals DNA in the process of transcription and reduces the size of intracellular DNA by supercoiling. Bacterial cell death occurs within 20 to 30 minutes after exposure. Ciprofloxacin is bactericidal and has good activity against many aerobic gram-positive and gram-negative bacteria. Many strains of Pseudomonas, Salmonella, Shigella, Camplyobacter, Yersinia, Brucella, Listeria and several Mycobacteriums are sensitive to ciprofloxacin. Ciprofloxacin also has good activity against many streptococcal and staphylococcal bacteria. It is inactive against most anaerobes, such as Bacteroides and Clostridium, and Nocardia is also routinely resistant to ciprofloxacin.

Resistance to ciprofloxacin and other fluoroquinolones is slow to develop. Plasmid-mediated resistance does not occur. Like other fluoroquinolones, the effects of ciprofloxacin are often additive to other antibiotics, such as the aminoglycosides, beta-lactam agents, clindamycin and metronidazole.

Systemic ciprofloxacin is metabolized by the liver and kidneys. It is excreted in the urine and some of the drug is also eliminated in the feces. Ophthalmic ciprofloxacin is absorbed into the systemic circulation following topical administration; however, there is no apparent systemic absorption following use of the otic form of the drug.

In the United States, ciprofloxacin is a prescription drug.

This drug has not been specifically approved and labeled for use in animals by the Food and Drug Administration. There is enough state of the art information published on its use in dogs, so that veterinarians can prescribe it legally as an extra-label drug.


This drug is registered for use in humans only. 
Human formulations: Oral preparation - Cipro® (Bayer), IV preparation - Cipro® I.V. (Bayer), Otic preparation - Cipro® HC Otic (Alcon) and Ophthalmic preparation - Ciloxan® (Alcon)
Veterinary formulations: None


Systemic ciprofloxacin is used primarily in the treatment of susceptible bacterial osteomyelitis. It is believed that ciprofloxacin has superior penetration in bone when compared with enrofloxacin. The systemic drug may also be used selectively in other cases, such as the enteric infections or as indicated by bacterial sensitivity testing

Topical ciprofloxacin is used for a variety of aerobic infections of the cornea and external ear canal. It is particularly good against multiple resistant bacterial infections of the ear and cornea.


Ciprofloxacin should not be used in animals with known hypersensitivity or allergy to the drug. It should also be avoided in young animals.

The most significant side effect associated with ciprofloxacin is cartilage damage. Bubble-like damage in the articular cartilage has been reported when ciprofloxacin, or any fluoroquinolone, is administered to small or medium sized dogs less than eight months of age, or in large or giant breed dogs before they reach full maturity, which may take up to two years, depending on the breed. Articular cartilage changes most often occur in animals between four to 28 weeks of age and when they are given two to five times the recommended dosage for over 30 days. Clinical signs associated with articular cartilage damage usually are not seen unless five times the dose is administered. Articular damage has not been demonstrated with the topical forms of ciprofloxacin.

Ciprofloxacin has been associated with crystalluria in humans so animals receiving ciprofloxacin should not be allowed to become dehydrated. In addition, ciprofloxacin has been associated with CNS stimulation in humans so it should be used with caution in animals with seizure disorders.

Animals with pre-existing renal and hepatic dysfunction may require a reduction in dose.

Ciprofloxacin has a good safety record and adverse reactions are uncommon. Occasionally, some animals develop anorexia, vomiting or diarrhea from ciprofloxacin.


When used concurrently with antacids, ciprofloxacin may be bound, with subsequent prevention of gastrointestinal absorption. Sucralfate may also inhibit absorption. For this reason, at least two hours should pass before sucralfate or antacids are administered after ciprofloxacin has been given.

When used concurrently with theophylline, ciprofloxacin may cause theophylline blood levels to rise. When used with cyclosporine, nephrotoxicity may be exacerbated.

Synergism may occur when ciprofloxacin is combined with 3rd generation cephalosporins, aminoglycosides, clindamycin, metronidazole, and some penicillins.


Oral ciprofloxacin is available in tablets of 100, 250, 500 and 750 mg size and as a 5% and 10% suspension. It is also available in an intravenous form in concentrations of 2 mg/ml and 10 mg/ml.

Ciprofloxacin otic is supplied as a suspension containing 2 mg ciprofloxacin and 10 mg hydrocortisone in a 10 ml bottle. Ciprofloxacin ophthalmic is supplied as a 0.3% solution in 2.5ml, 5 ml, or 10 ml bottles, and as a 0.3% ointment in a 3.5 gm tube.

Ciprofloxacin should be stored at room temperature and protected from moisture. Fluoroquinolones should also be protected from strong ultraviolet light.


Oral ciprofloxacin is typically given at 11 to 15 mg/kg PO every 12 hours.

Topical ophthalmic ciprofloxacin may be given as frequently as every two hours, and the otic suspension is usually instilled twice daily.


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Vaden SL and Papich MG: Empiric Antibiotic Therapy. In Kirk RW and Bonagura JD (eds): Current Veterinary Therapy XII. Philadelphia, WB Saunders Co, 1995, p. 278.

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