Determination of the route of excretion of robenacoxib (Onsior™) in cats and dogs: A pilot study.

Abstract

The objective of the studies was to determine the route of excretion, faecal or urinary, of the nonsteroidal anti-inflammatory drug (NSAID) robenacoxib (Onsior™) in cats and dogs. The studies employed a two-part crossover design in 4 beagle dogs (2 female and 2 male, age 36-41months and body weight 9.0-10.3kg) and a parallel group comparison of two groups each of 3 domestic short-hair cats (2 female and 4 castrated male, age 35-73months and body weight 3.0-5.7kg). Animals were administered single doses of 1 (dog) or 2 (cat) mg/kg of [14 C]-robenacoxib by intravenous (IV) and oral routes. Venous blood samples were taken and analysed for robenacoxib concentration. Faeces and urine were collected for 4 (cats) or 7 (dogs) days and analysed for radioactivity. Robenacoxib was eliminated rapidly from blood (≤ 8hr). In dogs, expressed as the percentage of the administered dose and adjusted so that faecal plus urine recovery was 100%, the mean (SD) excretion in faeces and urine was, respectively, 64.6% (4.30) and 35.4% (4.3) after IV and 66.7% (6.9) and 33.3% (6.9) after oral administration. The respective values in cats, in faeces and urine, were 72.5% (4.6) and 27.5% (4.6) after IV and 78.5% (2.6) and 21.5% (2.6) after oral administration. In conclusion, excretion of systemically available robenacoxib in cats and dogs was mixed via both faeces and urine, but predominately faecal (~64.6% in dogs and ~72.5% in cats) and assumed to be via biliary excretion.