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

This research article assesses the effectiveness and behavior of the anti-inflammatory drug phenylbutazone in southern white rhinoceros. Administered orally, the drug exhibited a peak concentration at 1.8 hours and an elimination half-life of 9 hours, similar to responses recorded in horses. Accumulation of the drug was determined to be mild in a multiple-dose trial.

Research Context

• The southern white rhinoceros often experiences painful conditions like traumatic injuries or osteoarthritis, requiring pain management drugs.
• A commonly used medication is the non-steroidal anti-inflammatory drug, phenylbutazone, due to its easy oral application and familiarity from its use in horses.

Research Methodology

• The research involved administering a single dose of 2 mg/kg of phenylbutazone to 33 healthy adult rhinoceros across six North American zoos.
• The researchers took four blood samples from each animal at specified intervals ranging from immediately after administration up to 48 hours later.
• An analysis of the drug was carried out using high-performance liquid chromatography.

Research Results

• With the use of nonlinear mixed-effects modeling, they determined the population pharmacokinetic parameters.
• The calculated peak concentration (C) was 3.8 µg/ml, occuring 1.8 hours after administration with an elimination half-life of 9 hours.
• The results matched those reported for horses and remained within the half maximal effective concentration for horses for nearly 10 hours.

Additional Study

• The researchers also conducted a multi-dose trial in which five rhinoceros received 2 mg/kg orally once daily for five consecutive days.
• Results showed a mild accumulation of the drug at a predicted factor of 1.2.
• This research provides the inaugural set of pharmacokinetic data for any rhinoceros species subjected to phenylbutazone treatment.