Pharmacokinetic, biochemical and tolerance studies on carprofen in the horse

Carprofen, a non-steroidal anti-inflammatory drug (NSAID) was administered to three Thoroughbred geldings and three Shetland ponies to determine its plasma disposition and tolerance. The main pharmacokinetic characteristics of carprofen in horses and ponies were a volume of distribution of 0.08 to 0.32 litres/kg (mean +/- se = 0.23 +/- 0.04) a systemic clearance of 26.4 to 78.5 ml/min (mean +/- se = 44.9 +/- 8.0) and a plasma elimination half-life of 14.5 to 31.4 h (mean +/- se = 21.9 +/- 2.3). There was no evidence of any accumulation of carprofen in plasma when the drug was given orally at a dose rate of 0.7 mg/kg for 14 consecutive days. Carprofen was well tolerated following intravenous (iv) and oral administration. Intramuscular (im) administration resulted in elevated levels of plasma creatine kinase suggesting muscle cell damage. According to the results of this study carprofen can be regarded as a long-acting NSAID in horses from a pharmacokinetic point of view. Either iv, im or the oral route of administration could be used to achieve high carprofen plasma concentrations.