Pharmacokinetics of a single oral dose of flunixin meglumine in the white rhinoceros (Ceratotherium simum).
Flunixin meglumine, a nonsteroidal anti-inflammatory medication, has been used in rhinoceros species at doses extrapolated from domestic animals. There is increasing evidence to suggest significant variations exist in metabolism of drugs in exotic species. Due to the differences in drug metabolism, dose extrapolation from domestic animals may not be appropriate for exotic species. The objective of this study was to investigate the pharmacokinetics of flunixin meglumine in five white rhinoceroses (Ceratotherium simum) administered a single (1 mg/kg) oral dose of a commercial equine flunixin meglumine paste. Concentrations of flunixin and its metabolite 5-OH flunixin were analyzed, and pharmacokinetic parameters were estimated for each animal. Mean observed plasma concentrations peaked at 1,207±601 ng/ml and occurred at 3±1 hr. The geometric mean of the apparent elimination half-life after oral administration was 8.3±1.2 hr. This data suggests that flunixin meglumine appears to be slowly metabolized or slowly absorbed in this species. No adverse clinical effects were observed during the study period. A single dose of 1 mg/kg appears safe for use in the white rhinoceros. Multidose studies are needed to determine if plasma accumulation of flunixin meglumine occurs and to evaluate safety.