Comparison of medetomidine and dexmedetomidine as premedicants in dogs undergoing propofol-isoflurane anesthesia

Objective-To compare 3 dose levels of medetomidine and dexmedetomidine for use as premedicants in dogs undergoing propofol-isoflurane anesthesia. Animals-6 healthy Beagles. Procedure-Dogs received medetomidine or dexmedetomidine intravenously at th e following dose levels: 0.4 mug of medetomidine or 0.2 mug of dexmedetomid ine/kg of body weight (M0.4/D0.2), 4.0 mug of medetomidine or 2.0 mug of de xmedetomidine/kg (M4/D2), and 40 mug of medetomidine or 20 mug of dexmedeto midine/kg (M40/D20). Sedation and analgesia were scored before induction. A nesthesia was induced with propofol and maintained with isoflurane. End-tid al isoflurane concentration, heart rate, and arterial blood pressures and g ases were measured. Results-Degrees of sedation and analgesia were significantly affected by do se level but not drug. Combined mean end-tidal isoflurane concentration for all dose levels was higher in dogs that received medetomidine, compared wi th dexmedetomidine. Recovery time was significantly prolonged in dogs treat ed at the M40/D20 dose level, compared with the other dose levels. After in duction, blood pressure decreased below reference range and heart rate incr eased in dogs treated at the M0.4/D0.2 dose level, whereas blood pressure w as preserved in dogs treated at the M40/D20 dose level. However, dogs in th ese latter groups developed profound bradycardia and mild metabolic acidosi s during anesthesia. Treatment at the M4/D2 dose level resulted in more sta ble cardiovascular effects, compared with the other dose levels. In additio n, Paco(2) was similar among dose levels. Conclusions and Clinical Relevance-Dexmedetomidine is at least as safe and effective as medetomidine for use as a premedicant in dogs undergoing propo fol-isoflurane anesthesia.