Buprenorphine is a common analgesic administered to rabbits and high concentration formulations can reduce handling stress without sacrificing pain relief. The objective of this study was to evaluate the pharmacokinetics of high concentration buprenorphine and its metabolites following multiple subcutaneous doses in the rabbit. Laboratory variables (complete blood cell count, biochemistry profile, urinalysis) were compared for drug effects and injection sites were evaluated via histopathology.

High concentration buprenorphine (HCB) was administered subcutaneously (0.24 mg/kg) to six, 17-week-old, intact female, New Zealand white rabbits (Oryctolagus cuniculus) for three doses, 24 hours apart. Two control animals received an equal volume of saline. Blood samples were collected at -72, 0, 0.33, 0.66, 1.5, 3, 6, 12, 24, 48, 72, 96, 120, and 144 hours. Buprenorphine and its metabolites were measured via liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS). Blood and urine profiles were collected prior to and following HCB administration and compared within and between groups. Injection sites and major organ systems were evaluated grossly and microscopically for drug effects.