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Enrofloxacin for Veterinary Use
by Barbara Forney, VMD
Enrofloxacin is a broad-spectrum bactericidal antibiotic. Although the mechanism of action is not well understood, Enrofloxacin is effective against a broad spectrum of gram- positive and gram-negative bacteria including most species of the following: Pseudomonas aeruginosa, Klebsiella, E.coli., Enterobacter, Campylobacter, Shigella, Salmonella, Aeromonas, Haemophillus, Proteus, Yersinia, Serratia, Vibrio, Brucella, Chlamydia, Staphylocci
(including some methicillin
resistant strains), Mycoplasma and Mycobacterium
It is not effective against anaerobic bacteria and may be variably effective against Streptococcus
infections. Enrofloxacin has a similar spectrum of activity as ciprofloxacin but enrofloxacin has been shown to have better bioavailability. With the exception of cerebral spinal fluid, enrofloxacin attains therapeutic levels in most tissues of the body. This makes it a very attractive antibiotic choice for difficult to treat infections, particularly those that need long-term antibiotics. Some examples might be osteomyelitis, sinus infections, otitis, difficult soft tissue infections, peritonitis, and pleuritis or pneumonia.
Enrofloxacin is eliminated by both renal and hepatic metabolism. Animals with impaired kidney or liver function may need extra monitoring and dose adjustments to prevent excess drug accumulation.
Dogs and Cats
Enrofloxacin is approved for use in dogs and cats. In dogs it may be given orally, intramuscularly or intravenously. It is approved only for oral use in cats although there is published information regarding intramuscular use. One of the positive features of enrofloxacin is that it is absorbed well orally and in many cases may be given once per day.
Fluroquinolones including enrofloxacin have been shown to cause articular cartilage abnormalities when the drug is given at high dose-levels. The age and breed of the patient should be considered when using enrofloxacin. Large and giant breeds may be more at risk because of a longer period of growth. Enrofloxacin has been shown to be safe in pregnant dogs and lactating dogs, however because of the problems with articular cartilage it should be avoided unless the benefits clearly outweigh the risk to the puppies. This work has not been repeated in cats.
Enrofloxacin is well-absorbed orally and intravenously. It generally is not used intramuscularly because it is too irritating. Although studies have not been done in the horse, there is the risk of developmental cartilage abnormalities with the fluorquinolone antibiotics. Since horses are expected to be athletes, the use of enrofloxacin in the young horse should be weighed carefully against the potential risk of cartilage abnormality.
- Enrofloxacin and the other fluroquinolone antibiotics can cause developmental cartilage abnormalities. As a consequence most veterinarians try to avoid these drugs in young animals.
GI side-effects including vomiting, diarrhea and elevated liver enzymes; Rare CNS signs including ataxia, seizures, depression and anxiety.
GI side effects include vomiting, diarrhea, anorexia, elevated liver enzymes. CNS signs include ataxia, seizures, depression, vocalization and aggression. Rare ocular toxicity may occur.
When injectable enrofloxacin is given orally, it can cause mucous membrane irritation, redness, slobbering and swelling.
- Animals with severe kidney or liver problems may need a reduced dose of enrofloxacin. Hydration should be monitored and fluid therapy used in animals at risk for dehydration.
- Enrofloxacin should be used with caution or avoided in animals at risk for seizures. This drug is not used in humans due to central nervous system stimulation.
- Enrofloxacin should not be used for regional antibiotic perfusion because it is too irritating and will cause vasculitis.
About the Author
Dr. Barbara Forney is a veterinary practitioner in Chester County, Pennsylvania. She has a master's degree in animal science from the University of Delaware and graduated from the University of Pennsylvania School of Veterinary Medicine in 1982.
She began to develop her interest in client education and medical writing in 1997. Recent publications include portions of The Pill Book Guide to Medication for Your Dog and Cat, and most recently Understanding Equine Medications published by the Bloodhorse.
Dr. Forney is an FEI veterinarian and an active member of the AAEP, AVMA, and AMWA.
You can purchase books by Dr. Forney at
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