Effects of acepromazine or methadone on midazolam-induced behavioral reactions in dogs

This study evaluated whether acepromazine or methadone reduced behavioral parameters, overall excitement, and activity associated with midazolam administration to healthy dogs. Dogs received midazolam (M) alone [M: 0.25 mg/kg body weight (BW)] or with methadone (MM) (MM: 0.75 mg/kg BW) or acepromazine (MA) (MA: 0.03 mg/kg BW) or saline (S) solution alone, all intramuscularly. Two blinded observers evaluated behavioral parameters using video recordings 30 min before and after injection of drugs. Accelerometery was used to evaluate "total activity counts" (TAC) at baseline and post-treatment. Post-treatment excitement scores were significantly higher in M and MA compared to baseline, M and MM compared to S. and M compared to MA. Behavioral parameters showed significantly higher proportions of "pacing" post-treatment in all groups receiving midazolam, and "restlessness," "chewing/licking," and "sniffing" in M. No significant differences were found for TAC at baseline and post-treatment. Midazolam-induced paradoxical behavioral changes (excitation, panting, pacing, restlessness, licking/chewing, and vocalization) were not prevented by acepromazine or methadone in healthy dogs.