Why the Use of Ciprofloxacin in Companion Animals is a Bad Idea
Richard Brown, DVM - Clinical Practitioner's Advisory Committee representing AAFP

Veterinary pharmacologists are noticing an increasingly popular trend in companion animal veterinarian’s antibiotic choices that is causing considerable concern.  This choice is the use of Ciprofloxacin for dermatological and genitourinary infections.  Enrofloxacin, which is an approved veterinary drug, has been widely and successfully used for many years for these conditions.  Enrofloxacin is a moderately priced antimicrobial.  Ciprofloxacin has recently been made available in a generic form at small fraction of the cost of Enrofloxacin, a fact not lost on veterinarians seeking to provide treatment at a reduced cost to their patients.

The reason why the use of Ciprofloxacin, especially in canines and felines is not a sound medical decision is that the drug has a marked problem with bioavailability in these species.  According to pharmacologists who have expressed concern about Ciprofloxacin, the drug is only 40% available to dogs and in cats the bioavailability is as low as 20%.  This compares to humans who absorb almost 100% of oral Ciprofloxacin.  Enrofloxacin, which has good bioavailability is in fact metabolized to several active compounds, one being Ciprofloxacin.

Probably more important than being a poorly absorbed drug is the fact that Ciprofloxacin is a very important human drug.  Ciprofloxacin is currently the drug of choice for the control of bioterrorist spread Anthrax infection.  It is also considered important in treating Campylobacter diarrhea in people.  For many years the FDA has been focused on antibiotic use in food animals and antibiotic residues in the food supply.  Now the FDA is taking a very close look at antibiotic use in pet animals.  The concern is that overuse could lead to increased antibiotic resistance in bacterial populations and render these drugs ineffective for human medical conditions.  A possible outcome is that the FDA could restrict all fluoroquinolones for pet animal use as has recently been done in the poultry industry.

If a veterinary practitioner feels that a medical condition requires the use of an antibiotic in this class, it would be most prudent to choose a drug that is an FDA approved veterinary drug.