Objective.

The aim of this study was to compare tissue and plasma concentrations of florfenicol (FFC) and its metabolite florfenicol amine (FFC-a) between sheep and rabbits, after intramuscular administration of 20 mg FFC/kg.

Materials and methods.

Five Suffolk Down sheep and six New Zealand rabbits were used in this study. Blood samples were collected before FFC administration and at 0.25, 0.5, 1, 1.5, 2, 3 and 4 hours after treatment. At 4 hours after treatment, euthanasia was applied to animals. Plasma and tissue concentrations of FFC and FFC-a were determined by HPLC.

Results.

For FFC, maximum plasma concentrations, absorption rate, absorption half-life, distribution rate, and area under the plasma concentration-time curve were all found to be significantly higher in rabbits than in sheep. Similarly, for FFC-a, significantly higher maximum plasma concentrations and area under the concentration-time curve were observed in rabbits as compared to sheep. The metabolite ratio was higher in rabbits (12.7±3.07%) compared to sheep (3.99±0.87%) (p<0.05), as were the tissue concentrations of FFC and FFC-a.

Conclusions.

Significant differences in the pharmacokinetics and tissue concentrations of FFC, and its metabolite FFC-a, were observed between these two animal species. The higher concentrations of FFC-a in rabbits indicate a greater level of FFC metabolism as compared to sheep. This should be considered when establishing dosage and frequency of FFC administration for rabbits.

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