PHARMACOKINETIC PROFILES OF ORAL PHENYLBUTAZONE, MELOXICAM, AND FIROCOXIB IN SOUTHERN BLACK RHINOCEROS (DICEROS BICORNIS MINOR).

Abstract

The pharmacokinetic profile of selected NSAIDs in southern black rhinoceros (Diceros bicornis minor) were studied. Phenylbutazone (PBZ), meloxicam (MEL), and firocoxib (FIR) were administered orally to five captive, black rhinoceros, and blood was collected at predetermined time points for NSAID quantification and noncompartmental pharmacokinetic (PK) analysis. Phenylbutazone 4.0 mg/kg PO q12h for three doses, MEL 0.3 mg/kg PO q24h administered twice, and a single oral dose of FIR 0.1 mg/kg, were tested with a minimum washout time of 2 wk. PBZ reached a median (range) peak concentration (C_max) of 9.42 (2.74-11.5) g/ml at a mean (range) time (T_max) of 6.00 (4.00 to >12.00) h, and the median (range) elimination half-life (T_1/2) was 6.07 (3.95-6.49) h. Phenylbutazone pharmacokinetic parameters for black rhinoceros in this study were similar to domestic horses. Meloxicam reached a median (range) C_max of 0.576 (0.357-0.655) µg/ml at a median (range) time (T_max) of 6.00 (4.00-12.00) h; the median (range) T_1/2 of MEL was 14.0 (12.4-17.9) h. These results demonstrate that once-daily administration of MEL at 0.3 mg/kg resulted in a serum concentration of greater than 0.200 µg/ml from 2 to 24 h in four animals, which is within the analgesic range (0.200-0.400 µg/ml) for this drug in other species postulated by other studies. A single dose of firocoxib (0.1 mg/kg) reached a median (range) peak concentration (C_max) of 15.7 (9.65-17.3) ng/ml at a median (range) T_max of 4.00 (4.00-6.00) h. The median (range) elimination T_1/2 of FIR was 4.96 (4.47-6.51) h, which is faster than in the horse. The data suggest that extrapolation from equine FIR dosage recommendations is inappropriate for black rhinoceros.