Comparison of a new metamizole formulation and carprofen for extended post-operative analgesia in dogs undergoing ovariohysterectomy

A newly developed slow-release tablet formulation of metamizole was compared with carprofen for postoperative analgesia in dogs undergoing ovariohysterectomy. Twenty-three dogs were randomly assigned to one of two groups, and administered 50 mg/kg metamizole PO (Group M) or 4 mg/kg carprofen PO (Group C) 1 h before anaesthetic induction and 24 and 48 h later. Anaesthesia was induced with propofol and maintained with isoflurane and fentanyl, after premedication with 0.005 mg/kg medetomidine and 0.3 mg/kg methadone IM. A blinded observer assessed post-operative sedation, and analgesia using a visual analogue scale, a dynamic interactive visual analogue scale, the Glasgow composite pain scale (GCPS), and a mechanical nociceptive threshold device (T = 0.5, 1, 2, 4, 8, 12, 18, 21, 24, 36, 45, 60 and 70 h after surgery). Rescue methadone was administered if the GCPS was >6/24 in ambulatory dogs, or >5/20 in non-ambulatory dogs. Plasma concentrations of test drugs were quantified. The dose range for metamizole was 39-.56 mg/kg. At T = 0.5 h sedation scores were significantly higher in Group C and GCPS scores were significantly higher in Group M. Three dogs required rescue methadone (Group M, n = 1; Group C, n = 2). Vomiting occurred post-operatively in 45% of dogs in Group M. Carprofen and metamizole were both well absorbed; peak concentrations occurred within 4-24 h, and 4-16 h for carprofen and metamizole, respectively. Both drugs provided adequate analgesia of similar duration. No side effects were observed with carprofen while vomiting was frequent following administration of metamizole. (C) 2015 Elsevier Ltd. All rights reserved.