Enrofloxacin is a synthetic, broad spectrum antimicrobial substance belonging to the fluoroquinolone group of antibiotics.

It is bactericidal in action with activity against many Gram positive and Gram negative bacteria and mycoplasmas. The mechanism of action of the quinolones is unique among antimicrobials - they act primarily to inhibit bacterial DNA gyrase, an enzyme responsible for controlling the supercoiling of bacterial DNA during replication. Resealing of the double stranded helix is inhibited resulting in irreversible degradation of the chromosomal DNA. The fluoroquinolones also possess activity against bacteria in the stationary phase by an alteration of the permeability of the outer membrane phospholipid cell wall but are inactive against strict anaerobes

The pharmacokinetics of enrofloxacin are such that oral and parenteral administration leads to similar serum levels. Enrofloxacin is lipid soluble and amphoteric and possesses a high distribution volume. Tissue levels 2-3 higher than that 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.

After subcutaneous administration of 7.5 mg/kg the mean peak plasma concentration is 0.8 µg/ml achieved within 6 hours. Enrofloxacin is partly metabolised in the liver. Approximately 45 per cent of the dose is excreted in the urine and 55 per cent in the faeces as active and metabolites.

Overdose: A dose of 25 mg/kg bodyweight administered for 15 consecutive days is tolerated without any clinical symptoms.

Clinical signs seen in gross overdosage include diarrhoea, ataxia, lameness and muscle tremors. In accidental overdosage there is no antidote and treatment should be symptomatic.