Evaluation of self-injurious behavior, food intake, fecal output, and thermal withdrawal latencies after injection of a high-concentration buprenorphine formulation in rats (Rattus norvegicus)

OBJECTIVE To evaluate effects of high-concentration buprenorphine (HCB) on self-injurious behavior, food intake, fecal output, and thermal withdrawal latencies in healthy rats. ANIMALS 8 Sprague-Dawley rats. PROCEDURES Rats received 4 SC treatments (HCB at 0.075, 0.15, or 0.30 mg/kg [HCB0.075, HCB0.15, and HCB0.30, respectively] or 5% dextrose solution [0.20 mL/kg]) in a randomized, crossover-design study. Self-injurious behavior was assessed for 8 hours after injection. Food intake and fecal output were assessed for predetermined periods before and after treatment and separated into 12-hour light and dark periods for further analysis. Withdrawal latencies were assessed before (time 0) and at predetermined times after injection. Data were compared among treatments and time points. RESULTS Self-injurious behavior was observed up to 8 hours after injection for all HCB, but not dextrose, treatments. Preinjection food intake and fecal output amounts were similar among groups and higher during the dark period than during the light period. Food intake after all HCB treatments was higher during the light period and lower during the dark period, compared with preinjection results for the same treatments and with postinjection results for dextrose administration. Light-period fecal output was lower after HCB0.15 and HCB0.30 administration, compared with preinjection values for the same treatments and postinjection values for dextrose administration. Percentage change in withdrawal latency was significantly higher than that at time 0 (ie, 0%) for only 1 treatment (HCB0.30) at 1 time point (1 hour after injection). CONCLUSIONS AND CLINICAL RELEVANCE Although HCB0.30 produced a degree of thermal hypoalgesia in healthy rats, self-injurious behavior and alterations in food intake and fecal output were detected, potentially affecting clinical utility of the treatment.