Phenylbutazone pharmacokinetics in southern white rhinoceros (Ceratotherium simum simum) after oral administration

Abstract

Southern white rhinoceros (Ceratotherium simum simum) frequently develop painful conditions, such as traumatic injuries or osteoarthritis, necessitating the administration of pain-relieving medications. One of the preferred treatments is the nonsteroidal anti-inflammatory drug phenylbutazone because of the availability of oral formulations and the familiarity of its use in horses. For the main study, a single oral dose of phenylbutazone at 2 mg/kg was administered to healthy adult rhinoceros (n = 33) housed at six North American zoological institutions. Each rhinoceros had up to four blood samples collected under voluntary behavioural restraint at up to four predetermined time points (0, 1, 1.5, 2, 3, 4, 6, 8, 10, 24, 30 and 48 h). Drug analysis was performed by high-performance liquid chromatography. The population pharmacokinetic parameters were calculated with nonlinear mixed-effects modelling, and analysis showed a peak concentration (C MAX ) of 3.8 µg/ml at 1.8 h and an elimination half-life of 9 h. The concentrations achieved were similar to what has been reported for horses and were within the half maximal effective concentration for horses for at least 10 h.A multi-dose trial in five rhinoceros receiving 2 mg/kg orally once daily for five days found mild accumulation at a predicted factor of 1.2. This study represents the first pharmacokinetic data of phenylbutazone in any rhinoceros species.

Pharmacokinetics of Oral Flunixin Meglumine, Meloxicam, or Gabapentin in Three Black Rhinoceros ( Diceros Bicornis )

“…However, pharmacokinetic analysis in rhinoceros species is possible and has been reported for flunixin meglumine (FM) and phenylbutazone in white rhinoceroses (WR; Ceratotherium simum ). 4,8 Due to species-specific differences, such as oxidative stressor sensitivity in black rhinoceroses (BR; Diceros bicornis ) and differences in the preferred diet between browsing BR and grazing WR, pharmacokinetic analysis of analgesic medications in BR is needed. Single-dose pharmacokinetics of oral and IV FM and meloxicam, and oral gabapentin, were completed in three BR.…”