• bioavailability.
• pharmacokinetics
• coxib
• goats
• NSAIDs
• Robenacoxib

Introduction: Robenacoxib is a cyclooxygenase-2 selective inhibitor used exclusively in veterinary medicine. Approved for use in cats and dogs, it has never been tested on goats. This study aimed to evaluate its pharmacokinetics in goats following single intravenous (IV), subcutaneous (SC) and oral (PO) administrations.
Materials and Methods: Five-month old healthy female goats (n=8) were used. The animals were subjected to a three-phase, two-dose (2 mg/kg IV, 4 mg/kg SC, PO) open, parallel study design, with a four-month washout period between the IV and SC treatment, and a one-week between the SC and PO treatment. Blood was drawn from the jugular vein in heparinized vacutainer tubes at predetermined times. The drug quantification was performed using a re-validated HPLC method (1). The data were pharmacokinetically analyzed using ThothProTM 4.3 software in a non-compartmental approach. Wilcoxon's rank-sum test was used to compare the data between the treatments (2).
Results: Plasma concentrations were quantifiable from 0.083 to 2 h after IV administration and from 0.25 to 6 h after extravascular (EV) administrations. The absolute Vd and Cl were 246 mL/kg and 522 mL/h/kg, respectively. For SC and PO, the mean peak plasma concentrations were 2.34 and 3.34 μg/mL at 1.33 and 0.51 h, respectively. The Vd was significantly higher in the EV groups than the IV group, which might have been attributed to the parallel study design, and the physiological and environmental shifts over a 4-month period. This caused an increase in HL (1.63 h PO, 1.4 h SC). The average SC and PO bioavailability were 98% and 91%, respectively. .
Conclusions: When administered intravenously, robenacoxib was quickly eliminated. Due to the larger EV Vd, the drug's HL was significantly longer following SC and PO treatments. Robenacoxib is not suitable for goats, unless it is administered frequently, due to the typically short HL.