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Pharmacological particulars
Pharmacotherapeutic group: Fluoroquinolones. ATCvet code: QJ01MA90
Pharmacodynamic properties
Enrofloxacin is a synthetic fluoroquinolone antibiotic that exerts its activity by inhibiting topoisomerase II, an enzyme involved in the mechanism of bacterial replication.
Enrofloxacin exerts bactericidal activity concentration-dependant with similar values of minimal inhibitory concentration and minimal bactericide concentrations. It also possesses activity against bacteria in the stationary phase by an alteration of the permeability of the outer membrane phospholipid cell wall.
In general, enrofloxacin exhibits good activity against most Gram-negative bacteria, especially those of the Enterobacteriacea. Escherichia coli, Klebsiella spp., Proteus spp., and Enterobacter spp. are generally susceptible.
Pseudomonas aeruginosa is variably susceptible and, when it is susceptible, usually has a higher MIC than other susceptible organisms.
Staphylococcus aureus and Staphylococcus intermedius usually are susceptible.
Streptococci, enterococci, anaerobic bacteria can generally be considered resistant.
Induction of resistance against quinolones can develop by mutations in the gyrase gene of bacteria and by changes in cell permeability towards quinolones.
According to the CLSI standard (CLSI July 2013), the veterinary breakpoints available for Enterobacteriaceae and Staphylococcus spp., are:
MICs values for enrofloxacin in dogs (skin, soft tissue, respiratory and UTI), S ≤ 0.5 μg/mL; I: 1_2 μg/mL; R ≥ 4μg/ml.
Pharmacokinetic properties
Enrofloxacin is rapidly metabolised to form an active compound, ciprofloxacin.
After oral administration of Xeden (5 mg/kg) in dogs:
- The maximal plasma concentration of enrofloxacin of 1.72 µg/mL was observed one hour following administration.
- The maximal plasma concentration of ciprofloxacin (0.32 µg/mL) was observed two hours following administration.
Enrofloxacin is primarily excreted via the kidneys. A major portion of the parent drug and its metabolites is recovered in urine.
Enrofloxacin is widely distributed in the body. The tissue concentrations are often higher than the serum concentrations. Enrofloxacin crosses the blood-brain barrier. The degree of protein binding in serum is 14% in dogs. The half-life in serum is 3-5 hours in dogs (5 mg/kg). Approximately 60% of the dose is excreted as unchanged enrofloxacin and the remainder as metabolites, amongst others ciprofloxacin. The total clearance is approximately 9 ml/minute/kg bodyweight in dogs.