Safety and clinical effectiveness of a compounded sustained-release formulation of buprenorphine for postoperative analgesia in New Zealand White rabbits.

OBJECTIVE: To determine the clinical effectiveness and safety of a compounded sustained-release formulation of buprenorphine, compared with effects of regular buprenorphine, for postoperative analgesia in rabbits.
DESIGN: Blinded randomized controlled clinical trial. ANIMALS: 24 purpose-bred adult male New Zealand White rabbits. PROCEDURES: Rabbits received titanium implants in each tibia as part of another study. Immediately prior to surgery, each rabbit received regular buprenorphine hydrochloride (0.02 mg/kg [0.009 mg/lb], SC, q 12 h for 3 days) or 1 dose of a compounded sustained-release formulation of buprenorphine (0.12 mg/kg [0.055 mg/lb], SC) followed by an equal volume of saline (0.9% NaCl) solution (SC, q 12 h for 3 days) after surgery. For 7 days after surgery, rabbits were evaluated for signs of pain by means of rabbit grimace and activity scoring and for adverse effects.
RESULTS: No significant differences were identified between treatment groups in grimace and activity scores at any point. No major adverse effects were detected for either drug. However, 3 rabbits that received regular buprenorphine had pain scores suggestive of moderate to severe pain by the time dose administration was due (ie, within the 12-hour administration interval). No clinically important differences were detected in intraoperative anesthetic or postoperative recovery variables. CONCLUSIONS AND CLINICAL RELEVANCE: Sustained-release buprenorphine administered SC at 0.12 mg/kg was at least as effective as regular buprenorphine in providing analgesia for rabbits following orthopedic surgery without any major adverse effects. This sustained-release formulation represents an important alternative for rabbit analgesia with potential to improve rabbit welfare over existing analgesic standards.