Evaluation of the analgesic properties of acepromazine maleate, oxymorphone, medetomidine and a combination of acepromazine-oxymorphone

ObjectiveTo determine the presence and duration of analgesia after oxymorphone, acepromazine maleate, acepromazine-oxymorphone combination and medetomidine administration in dogs.Study designBlinded, controlled study.AnimalsSix adult beagle dogs.MethodsEach dog participated in five trials receiving acepromazine maleate (0.2 mg kg^?1 IM), oxymorphone (0.2 mg kg^?1 IM), acepromazine-oxymorphone drug combination (0.2 mg kg^?1 each IM), medetomidine (20 μg kg^?1 IM) and sterile saline (control). Two specially designed instruments were used for analgesia determination: a heat device (HD) utilized a linear ramped intensity incandescent bulb and a pressure device (PD) consisted of a pneumatic cylinder that protruded a 2.5-cm bolt. The minimum pressure and heat necessary to produce an avoidance response were determined. Analgesia testing was performed prior to and at 30-minute intervals for six hours after drug administration.ResultsOxymorphone, acepromazine-oxymorphone and medetomidine significantly elevated both pressure and heat response thresholds compared to controls and acepromazine. Both medetomidine and acepromazine-oxymorphone provided a significantly longer duration of analgesia than oxymorphone. No adverse effects were observed at any of the thermal or pressure application sites.ConclusionsOxymorphone, medetomidine and acepromazine-oxymorphone produced significant analgesia with medetomidine and acepromazine-oxymorphone providing the longest duration of analgesia.