Pharmacotherapeutic group: antibacterials for systemic use, fluoroquinolones.
ATCvet code: QJ01MA90
Pharmacodynamic properties
Mode of action
Two enzymes essential in DNA replication and transcription, DNA gyrase and topoisomerase IV, have been identified as the molecular targets of fluoroquinolones. Target inhibition is caused by non-covalent binding of fluoroquinolone molecules to these enzymes. Replication forks and translational complexes cannot proceed beyond such enzyme-DNA-fluoroquinolone complexes, and inhibition of DNA and mRNA synthesis triggers events resulting in a rapid, drug concentration-dependent killing of pathogenic bacteria. The mode of action of enrofloxacin is bactericidal and bactericidal activity is concentration dependent.
Antibacterial spectrum
Enrofloxacin is active against many Gram-negative bacteria such as Escherichia coli, Klebsiella spp., Actinobacillus pleuropneumoniae, Pasteurella spp. (e.g. Pasteurella multocida), Bordetella spp., Proteus spp., Pseudomonas spp., against Gram-positive bacteria such as Staphylococcus spp. (e.g. Staphylococcus aureus) and against Mycoplasma spp. at the recommended therapeutic doses.
Types and mechanisms of resistance
Resistance to fluoroquinolones has been reported to arise from five sources, (i) point mutations in the genes encoding for DNA gyrase and/or topoisomerase IV leading to alterations of the respective enzyme, (ii) alterations of drug permeability in Gram-negative bacteria, (iii) efflux mechanisms, (iv) plasmid mediated resistance and (v) gyrase protecting proteins. All mechanisms lead to a reduced susceptibility of the bacteria to fluoroquinolones. Cross-resistance within the fluoroquinolone class of antimicrobials is common.
Pharmacokinetic particulars
The pharmacokinetic properties of enrofloxacin are such that both oral and parenteral administration leads to similar serum levels. Enrofloxacin possesses a high distribution volume. Tissue levels 2-3 times higher than found in the serum, have been demonstrated in laboratory animals and target species. Organs in which high levels can be expected are the lungs, liver, kidney, skin, bone and lymphatic system. Enrofloxacin also distributes into the cerebrospinal fluid, the aqueous humour and the foetus in pregnant animals.