The study was conducted in twelve healthy female dogs randomly divided into two groups of six animals each. One group was administered tramadol (2 mg/kg, IM) and another group was administered buprenorphine (0.01 mg/kg, IM) as preemptive analgesics, 30 minutes prior to atropine sulfate (0.04 mg/kg, IM) followed by diazepam (0.2 mg/kg, IV). In both groups, ovariohysterectomy from right flank region was performed under general anaesthesia induced by propofol (6.0 mg/kg) and maintained by propofol (4.0 mg/kg) by repeat bolus injections. Tramadol was repeated at the same dose rate after every six hours and buprenorphine was repeated at the same dose rate after every 12 hours up to second postoperative day.

Postoperative pain assessment (0-20 multifactorial numerical rating scale) was made at preoperative, immediate post recovery and 8, 24 and 48 hours postoperative stages. Blood biochemical, hematological and clinical parameters were also measured at same stages. Of the behavioural parameters, which included posture, vocalization, activity level, attitude, response to palpation, facial expression and mental status, activity level was found to be the least reliable whereas posture, the most reliable parameter for postoperative pain assessment. Mean total pain score at immediate post recovery stage in tramadol group was slightly lower than the buprenorphine group. Comparing between the two groups, mean plasma glucose concentration was significantly higher at immediate post recovery stage in buprenorphine group. Mean neutrophil and lymphocyte counts were significantly higher in buprenorphine than tramadol group at 48 hours postoperative stage. A marked cardiopulmonary depression in buprenorphine group was reported.