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

The effects of breed and routes of administration on the plasma pharmacokinetics and faecal excretion of robenacoxib in goats

Robenacoxib (RX) is a non-steroidal anti-inflammatory drug (NSAID) of the coxib class. This study aimed to evaluate the plasma dispositions and faecal excretion profiles of RX in Alpine and Saanen goats following oral and subcutaneous routes. Two different goat breeds were allocated into two treatment groups concerning the breed. RX was administered subcutaneously to animals at a dose of 4mg/kg b.w. Following a one-week washout period, RX was administered by oral route to the same animals at the same dose. Heparinized blood samples were collected from all animals before drug administration (0h) and subsequently up to 24h. Faecal samples were collected at various times between 8h and 36h. The concentrations of RX in plasma and faeces were determined by HPLC. The plasma half-life (T1/2λz) of RX in Saanen goats (1.21h) was significantly longer (P < 0.017) than in Alpine goats (0.90h) after subcutaneous administration. In both goat breeds, statistical differences were observed between subcutaneous and oral administration of RX for T1/2λz, Tlast, Cmax, AUC0-∞, and MRT0-∞. Faecal Cmax and Tmax parameters following oral administrations were 0.92µg/g and 0.85µg/g at 30h and at 24h in Alpine and Saanen goats, respectively. The difference in plasma protein ratio between Alpine and Saanen goats may have affected the T1/2λz of the drug. NSAIDs are among the drug groups frequently detected in aquatic and terrestrial ecosystems around the world and there are data on the effects of NSAID residues on wildlife and aquatic species. Therefore, revealing the excretion of NSAIDs, which are frequently used in the veterinary field, in faeces and urine should be considered for ecological sustainability.

Pharmacokinetics of robenacoxib following single intravenous, subcutaneous and oral administrations in Baladi goats (Capra hircus)

The purpose of this study was to assess the pharmacokinetics of robenacoxib (RX), a COX-2 selective non-steroidal anti-inflammatory drug, in goats after single intravenous (IV), subcutaneous (SC) and oral (PO) administrations. 5-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) unblinded, parallel study design, with a four-month washout period between the IV and SC treatment, and a one-week period between the SC and PO treatment. Blood was drawn from the jugular vein in heparinized vacutainer tubes at 0, 0.085 (for IV only), 0.25, 0.5, 0.75, 1, 1.5, 2, 4, 6, 8, 10 and 24 h. Plasma RX concentrations were measured using HPLC coupled to a UV multiple wavelength detector, and the data were pharmacokinetically analysed using ThothPro™ 4.3 software in a non-compartmental approach. Following IV administration, terminal elimination half-life, volume of distribution and total clearance were 0.32 h, 0.24 L/kg and 0.52 L/h/kg, respectively. For SC and PO, the mean peak plasma concentrations were 2.34 and 3.34 μg/mL at 1.50 and 0.50 h, respectively. The t1/2λz was significantly different between the IV and the extravascular (EV) administrations (0.32 h IV vs 1.37 h SC and 1.63 h PO), suggesting the occurrence of a flip-flop phenomenon. The significant difference in Vd values between IV (0.24 L/kg) and EV (0.95 L/kg SC and 1.71 L/kg; corrected for F %) routes might have also triggered the t1/2λz difference. The absolute average SC and PO bioavailability were high (98% and 91%, respectively). In conclusion, the IV administration of RX might not be suitable for goats, due to its short t1/2λz. The EV routes, however, appear to be convenient for the drug's occasional use.

Robenacoxib pharmacokinetics in sheep following oral, subcutaneous, and intravenous administration

The aim of this study was to evaluate the pharmacokinetics (PK) of robenacoxib (RX), a COX-2 selective non-steroidal anti-inflammatory drug, in sheep after single subcutaneous (SC), oral (PO), and intravenous (IV) administration. Five healthy female sheep underwent a three-phase parallel study design with a washout period of 4 weeks, in which sheep received a 4 mg/kg SC dose in phase 1, a 4 mg/kg PO administration in phase 2, and a 2 mg/kg IV administration in phase 3. Plasma RX concentrations were measured over a 48 h period for each treatment using HPLC coupled to a UV multiple wavelength detector, and the PK parameters were estimated using a non-compartmental method. Following IV administration, terminal elimination half-life, volume of distribution at steady state, and total clearance were 2.64 h, 0.077 L/kg, and 0.056 L/h kg, respectively. The mean peak plasma concentrations following SC and PO administrations were 7.04 and 3.01 μg/mL, respectively. The mean bioavailability following SC and PO administrations were 45.98% and 16.58%, respectively. The SC route may be proposed for use in sheep. However, the multi-dose and pharmacodynamic studies are necessary to establish more accurately its safety and efficacy in sheep.

Pharmacology, safety, efficacy and clinical uses of the COX-2 inhibitor robenacoxib

Robenacoxib is a veterinary‐approved non‐steroidal anti‐inflammatory drug (NSAID) of the coxib group. It possesses anti‐hyperalgesic, anti‐inflammatory and anti‐pyretic properties. Robenacoxib inhibits the cyclooxygenase (COX)‐2 isoform of COX selectively (in vitro IC₅₀ ratios COX‐1:COX‐2, 129:1 in dogs, 32:1 in cats). At registered dosages (2 mg/kg subcutaneously in dogs and cats, 1–4 mg/kg orally in dogs and 1–2.4 mg/kg orally in cats), robenacoxib produces significant inhibition of COX‐2 whilst sparing COX‐1. The pharmacokinetic (PK) profile of robenacoxib is characterized by a high degree of binding to plasma proteins (>98%) and moderate volume of distribution (at steady state, 240 ml/kg in dogs and 190 ml/kg in cats). In consequence, the terminal half‐life in blood (<2 h) is short, despite moderate body clearance (0.81 L/kg/h) in dogs and low clearance (0.44 L/kg/h) in cats. Excretion is principally in the bile (65% in dogs and 72% in cats). Robenacoxib concentrates in inflamed tissues, and clinical efficacy is achieved with once‐daily dosing, despite the short blood terminal half‐life. In dogs, no relevant breed differences in robenacoxib PK have been detected. Robenacoxib has a wide safety margin; in healthy laboratory animals daily oral doses 20‐fold (dog, 1 month), eight‐fold (cat, 6 weeks) and five‐fold (dog, 6 months) higher than recommended clinical doses were well tolerated. Clinical efficacy and safety have been demonstrated in orthopaedic and soft tissue surgery, and in musculoskeletal disorders in dogs and cats.