Analgesic and antihyperalgesic effects of dipyrone, meloxicam or a dipyrone–meloxicam combination in bitches undergoing ovariohysterectomy

Abstract

The analgesic and antihyperalgesic effects of dipyrone, meloxicam or a dipyrone–meloxicam combination were compared in dogs undergoing elective ovariohysterectomy. In a double-blinded, prospective, randomised design, 40 bitches premedicated with intramuscular pethidine (4 mg/kg) and anaesthetised with isoflurane received one of four intravenous treatments (n = 10 per group) before ovariohysterectomy: control (physiological saline), meloxicam (0.2 mg/kg), dipyrone (25 mg/kg) or dipyrone–meloxicam (25 mg/kg and 0.2 mg/kg, respectively). Glasgow composite measure pain scale (GCMPS) and mechanical nociceptive thresholds (MNT) were assessed before anaesthesia and at 1, 2, 3, 4, 6, 8, 12 and 24 h postoperatively. Rescue analgesia (0.5 mg/kg morphine) was administered intramuscularly if the GCMPS was ≥3.The GCMPS and MNT did not differ among groups. The frequency of rescue analgesia was significantly (P < 0.05) lower in the dipyrone group (30%) than in controls (50%), but there were no significant differences from the control group in bitches treated with meloxicam (70%) or dipyrone–meloxicam (40%). There was a significant reduction in the total number of rescue treatments in the dypyrone (n = 5) and dipyrone–meloxicam (n = 5) groups when compared with the control (n = 17) and meloxicam (n = 19) groups. Meloxicam and dipyrone–meloxicam significantly reduced the percentage of animals exhibiting severe pain during MNT measurements (30% and 0%, respectively) compared with the control group (50%). Dipyrone produced superior analgesia (reduced morphine consumption), while meloxicam produced better antihyperalgesia (fewer episodes of severe pain) in contrast to controls. When used in tandem, the beneficial effects were combined.