Physiologic and behavioral effects of long-acting subcutaneous and transdermal buprenorphine in rats

To investigate thermoregulation, thermal antinociception, food/kaolin intake, fecal output, and behavior following long-acting buprenorphine preparations in rats.

8 adult male rats (Rattus norvegicus) were administered long-acting SC buprenorphine (SB; 0.65 mg/kg), transdermal buprenorphine (TB; 10 mg/kg), and controls in a randomized, cross-over design.

Body temperature, self-injury, sedation, food/kaolin intake, fecal output, and thermal withdrawal latencies were measured 1, 4, 8, 12, 24, 48, and 72 hours posttreatment. Data analysis was performed with mixed linear models.

Self-injury was present between 1 and 12 hours and 4 and 12 hours following TB and SB, respectively; sedation was associated with TB at 12 to 24 hours. Withdrawal latencies were longer in both TB and SB groups than in the control group. Food intake decreased with time in all groups but was significantly lower 24 to 48 hours after TB and 24 to 72 hours after SB versus controls. Kaolin intake decreased from baseline 48 to 72 hours in the control group. Fecal output decreased from baseline 24 to 72 hours in all groups but was significantly lower than controls 24 hours following TB and 24 to 48 hours in SB. Body temperature increased from baseline at 1 hour, 1 to 12 hours, and 1 to 24 hours in the control, TB, and SB groups, respectively, and was significantly higher than the control group 1 to 72 hours following TB and 4 to 24 hours after SB. Transdermal buprenorphine and SB in normal rats produced antinociception, self-injurious behavior, hyperthermia, and decreased food/fecal output.

Although these buprenorphine preparations may produce antinociception, untoward effects such as hyperthermia, self-injurious behavior, and reduced food intake/fecal output may be seen.