Effects of acepromazine, hydromorphone, or an acepromazine-hydromorphone combination on the degree of sedation in clinically normal dogs.

OBJECTIVE: To determine the effects of IM administration of acepromazine, hydromorphone, or the acepromazine-hydromorphone combination on degree of sedation in clinically normal dogs and to compare 2 sedation scoring techniques.
DESIGN: Prospective, randomized, blinded, controlled trial. Animals-46 random-source dogs. PROCEDURES: Dogs were assigned to receive IM administrations of acepromazine (0.05 mg/kg [0.023 mg/lb]; [DOSAGE ERROR CORRECTED] n = 12), hydromorphone (0.1 mg/kg [0.045 mg/lb]; 11), acepromazine-hydromorphone (0.5 mg/kg and 0.1 mg/kg, respectively; 12), or saline (0.9% NaCI) solution (0.05 mL/kg [0.023 mL/lb]; 11). Sedation scores were determined at 0 (time of administration), 15, 30, 45, and 60 minutes by use of a subjective scoring system (SSS) and a simple numeric rating scale (NRS).
RESULTS: Acepromazine caused significantly greater sedation than did saline solution at 15, 30, 45, and 60 minutes. Acepromazine-hydromorphone caused significantly greater sedation than did saline solution at 15, 30, 45, and 60 minutes and than did hydromorphone alone at 30 minutes. Hydromorphone alone did not cause significantly greater sedation than did saline solution. All treatments, including saline solution, caused significantly greater sedation at 45 and 60 minutes, compared with sedation at time 0. There was a significant correlation (r(2) = 0.72) between scores obtained with the SSS and NRS, but the NRS was less sensitive for detecting clinically important sedation. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of acepromazine or acepromazine-hydromorphone caused sedation in clinically normal dogs, whereas administration of hydromorphone alone did not. The NRS was a less-reliable measure of sedation.