Enrofloxacin Veterinary uses, Pharmacokinetics, Side effects, Mechanism of action, Drug interactions, Precautions and contraindications

Enrofloxacin is a prototypical veterinary fluorinated quinolone developed exclusively for use in animals. It occurs as a pale yellow, crystalline powder that is slightly soluble in water. Enrofloxacin is related structurally to the human-approved drug ciprofloxacin, having an additional ethyl group on the piperazinyl ring. Like other quinolones, inhibition of DNA gyrase in susceptible bacteria is the primary mechanism of action.

Antimicrobial spectrum

Enrofloxacin has good activity against some gram-positive organism and many gram-negative bacilli and cocci including most species strains of Pseudomonas, Klebsiella, E.coli, Enterobacter, shigella, Camphylobacter, Salmonella, Haemophilus, Proteus, Serratia, Citrobacter, Yersinia and Vibrio. Other organisms susceptible to enrofloxacin include Brucella, Chlamydia, Staphylococcus and Mycobacterium species.

Pharmacokinetics

Enrofloxacin is well absorbed after oral administration with bioavailability of about 80% in dogs, 60% in adult horses and 40% in foals. The peak plasma concentration is attained within one hour of oral dosing. Absorption of enrofloxacin is nearly complete from IM or SC injection. It is distributed throughout the body including bone, synovial fluid, prostrate, aqueous humour and pleural fluid. It also accumulates in very high concentrations in WBCs. Enrofloxacin is eliminated primarily unchanged in urine, although up to 25% of the drugs is metabolised to active metabolite ciprofloxacin, which is subsequently metabolized to inactive metabolites. The elimination half-life of enrofloxacin in dogs and cats is approximately 4-5 hours and 6 hours, respectively.

Adverse effects

Adverse reactions to the enrofloxacin are limited. Cartilage deformities and joint growth disorders have been documented in young dogs, so it is contraindicated in growing dogs. Gastrointestinal disorders( vomiting and anorexia), crystalluria and CNS disorders (dizziness, stimulation) are similar to other fluorinated quinolones. Acute blindness has been reported in cats receiving high doses of enrofloxacin as it is retinotoxic.

Contraindications and precautions

Quinolones are contraindicated in patients hypersensitive to the group. They are not recommended in growing dogs under 12 (small medium breeds) to 18 (large breeds) months of age due to inhibition of the growth of load bearing articular cartilage. They should be used with extreme care in pregnant animals and in patients with seizures disorders. As quinolones have tendency to cause crystalluria in acid urine, animals should not be allowed to become dehydrated. Patients with renal insufficiency may require dosage adjustments to prevent drug accumulation. Quinolones should not be used in patients with a know predisposition to arrhythmias (e.g. hypokalaemia and bradycardia) or in patients those are receiving antiarrhythmic drugs or other medications which might prolongs the QTc.  

Drug Interactions

Quinolones are potent chelators of Mg⁺⁺, Ca⁺⁺, Zn⁺⁺, Fe⁺⁺, and Al⁺⁺⁺,  so products containing multivalent  cations, including sucralfate, non-systemic antacids, nutritional supplements, and multivitamin and mineral supplements taken within two or four hours of orally administered quinolones may interfere with their absorption. Probenecid is reported to block tubular secretion of some quinolones and may increase their blood levels and half-lives. Quinolones inhibit biotransformation of theophylline, resulting in its prolonged and potentially toxic levels. The combination of fluorinated quinolones with non-steroidal anti-inflammatory drugs increases the potential of fluoroquinolones to lower seizure threshold. Simultaneous use of corticosteroids has been associated with almost one-third of quinolones-associated tendon rupture in animals. A synergistic effect of quinolones with beta-lactam, aminoglycoside, clindamycin or metronidazole antibacterials has been reported.

Clinical Uses

Enrofloxacin is approved for use in dogs and cats and some other species like cattle, swine and poultry for the treatment of diseases caused by organisms susceptible to it. The treatment includes infections of skin, urinary tract and soft tissues in dogs and cats. The activity against mycoplasma suggests usefulness in respiratory diseases in cattle and enzootic pneumonia in pigs. Enrofloxacin is also recommended in most exotic animal species because of its safety and activity against a variety of pathogens.  

Brand Name

Enrox