Carprofen as an analgesic for postoperative pain in cats: Dose titration and assessment of efficacy in comparison to pethidine hydrochloride

The aim of this study was to titrate the optimal dose of carprofen for single dose usage, for alleviating postoperative pain, under a double-blind and randomised protocol, using both negative and positive controls. Renal tolerance was assessed by screening plasma urea and creatinine. Pre- and postoperative assessment of pain and sedation was made using a dynamic and interactive visual analogue scoring system in 60 cats undergoing ovariohysterectomy. The cats were randomly assigned to one of six groups: (1) carprofen at 1-0 mg/kg subcutaneously (sc); (2) carprofen at 2-0 mg/kg sc; (3) carprofen at 4-0 mg/kg sc; (4) pethidine at 5-0 mg/kg intramuscularly (im), (5) pethidine at 10-0 mg/kg im; and (6) no analgesics (injection of saline). All injections were given postoperatively on tracheal extuba-tion and administered in a double-blind manner. Assessments were made up to 20 hours post extubation. Prior to induction and at 20 hours post extubation, blood samples were taken for laboratory analysis of the urea and creatinine content to check for any adverse effect on renal function. Cats given pethidine did not appear more sedated than the groups receiving carprofen or saline. Cats receiving carprofen were in less pain postoperatively overall, with 4-0 mg/kg being the most effective dose rate (significantly better than the other doses of carprofen at four and eight hours post extubation). The highest dose of pethidine provided significantly better analgesia than the highest dose of carprofen up to two hours post extubation, but from two to 20 hours post extubation carprofen at 4-0 mg/kg provided significantly better analgesia than the pethidine. None of the analgesic regimens appeared to affect renal function adversely, as measured by urea and creatinine levels.