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 the following dose
levels: 0.4 µg of medetomidine or 0.2 µg of
dexmedetomidine/kg of body weight (M0.4/D0.2), 4.0
µg of medetomidine or 2.0 µg of dexmedetomidine/
kg (M4/D2), and 40 µg of medetomidine or 20 µg
of dexmedetomidine/kg (M40/D20). Sedation and
analgesia were scored before induction. Anesthesia
was induced with propofol and maintained with
isoflurane. End-tidal isoflurane concentration, heart
rate, and arterial blood pressures and gases were
Results—Degrees of sedation and analgesia were
significantly affected by dose level but not drug.
Combined mean end-tidal isoflurane concentration for
all dose levels was higher in dogs that received
medetomidine, compared with dexmedetomidine.
Recovery time was significantly prolonged in dogs
treated at the M40/D20 dose level, compared with
the other dose levels. After induction, blood pressure
decreased below reference range and heart rate
increased in dogs treated at the M0.4/D0.2 dose
level, whereas blood pressure was preserved in dogs
treated at the M40/D20 dose level. However, dogs in
these latter groups developed profound bradycardia
and mild metabolic acidosis during anesthesia.
Treatment at the M4/D2 dose level resulted in more
stable cardiovascular effects, compared with the
other dose levels. In addition, PaCO2 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
propofol-isoflurane anesthesia. (Am J Vet Res