PHARMACOKINETICS OF MULTIPLE-DOSE ADMINISTRATION OF ELTENAC IN HORSES

Objective-To compare pharmacokinetics of eltenac after first and last IV administrations (0.5 mg/kg), using a multiple dosing schedule. Anim als-6 adult mares. Procedure-Eltenac (50 mg/ml) was administered IV at a dosage of 0.5 mg/kg of body weight every 24 hours for days 0 throug h 4. On days 0 and 4, blood samples were collected before, then period ically for 8 hours after eltanac administration. Concentration of elte nac in plasma samples was determined by use of high-performance liquid chromatography. Results-On day 0, median area under the plasma eltena c concentration versus time curve (AUC) was 6.77 mu g.h/ml (range, 5.6 1 to 8.08 mu g.h/ml), median plasma clearance was 1.23 ml/min/kg (rang e, 1.03 to 1.40 ml/min/kg), and median steady-stale volume of distribu tion was 191 ml/kg (range, 178 to 218 ml/kg). Median terminal half-lif e of eltenac was 2.36 hours (range, 2.30 to 2.98 hours). On day 4, med ian eltenac AUC was 6.70 mu g.h/ml (range, 5.21 to 7.44 mu g.h/ml), me dian plasma clearance was 1.23 ml/min/kg (range, 1.12 to 1.53 ml/min/k g), and median steady-state volume of distribution was 193 ml/kg (rang e, 172 to 205 ml/kg). Median terminal half-life of eltenac was 2.40 ho urs (range, 2.11 to 3.25 hours). Protein binding of eltenac, determine d by ultrafiltration, was > 99% at a total plasma concentration of 36 mu g/ml. Conclusion-Pharmacokinetic variables determined for each hors e were not different between days 0 and 4. Clinical Relevance-Under co nditions of this study, there was no clinically relevant accumulation of eltenac in equine plasma or alteration of pharmacokinetic variables after multiple IV dosing of 0.5 mg/kg of eltenac.