Pharmacotherapeutic group: Fluoroquinolone antibiotics
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-dependent with similar values of minimal inhibit 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 Enterobacteriaceae. Escherichia coli, Enterobacter spp., Klebsiella spp. and Proteus 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.
Pharmacokinetic properties
Enrofloxacin is approximately 100% bioavailable after oral administration. It is unaffected by food. Enrofloxacin is rapidly metabolized to form an active compound, ciprofloxacin.
After a dose of 5 mg/kg body weight, maximum plasma levels of approximately 1.5 µg/ml in dogs and approximately 2.5 µg/mL in cats are reached after 0.5-2.0 hours.
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 and 8% in cats. The half-life lies between 3.0 and 6.8 hours for dogs and cats, respectively.
Approximately 25% of the dose of enrofloxacin is excreted in the urine and 75% via the faeces. Approximately 60% (dogs) or 15% (cats) of the dose is excreted as unchanged enrofloxacin in the urine and the remainder as metabolites, amongst others ciprofloxacin. The total clearance is approximately 9 ml/minute/kg body weight.