The aim of this study was to determine the pharmacokinetics and bioavailability of carprofen in sheep following single intravenous (IV), intramuscular (IM), subcutaneous (SC), and oral (PO) administrations of a parenteral formulation at a dose of 4 mg/kg. A total of eight sheep were used for the investigation. The study comprised four periods, according to a crossover design with a 21-day washout period between treatments. Plasma concentrations of carprofen were measured using HPLC-UV. Pharmacokinetic parameters were estimated by non-compartmental model analysis. Following IV administration, t1/2ʎz , ClT , and Vdss were 43.36 h, 1.98 ml/h/kg, and 121.36 ml/kg, respectively. The Cmax(obs) was 26.57 mg/ml for the IM, 23.76 mg/ml for the SC, and 15.90 mg/ml for the PO. The bioavailability following IM, SC, and PO administrations was 75.47%, 82.00%, and 62.51%, respectively. Plasma creatine kinase activity increased significantly at 3, 6, and 12 h following IM administration of carprofen. Despite differences in plasma concentrations and bioavailability among administration routes, carprofen at 4 mg/kg dose may provide the plasma concentration (>1.5 μg/ml) needed for analgesic effect during 144 h in all routes. However, because of the slow absorption rate after SC and PO routes, the IV route may be preferred primarily for the rapid onset in the analgesic and anti-inflammatory effect of carprofen in sheep. Despite the favorable kinetics, the muscle damage caused by IM injection limits use of carprofen via IM route.
Keywords: bioavailability; carprofen; pharmacokinetics; sheep.
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