Objective—To compare hydromorphone with oxymorphone,
with or without acepromazine, for preanesthetic
sedation in dogs and assess changes in
plasma concentration of histamine after drug administration.
Design—Randomized clinical study.
Animals—10 healthy mixed-breed dogs.
Procedure—Dogs were treated IM with hydromorphone
(group H), oxymorphone (group O), hydromorphone
with acepromazine (group H/A), or oxymorphone
with acepromazine (group O/A). Sedation score, heart
rate, respiratory rate, systolic blood pressure, and oxygen
saturation were recorded at baseline immediately
after drug administration (T0) and every 5 minutes for 25
minutes (T25). Plasma histamine concentration was
measured at baseline and T25.
Results—Sedation was similar between groups H
and O at all times. Sedation was significantly greater
for groups H/A and O/A from T10 to T25, compared
with other groups. Systolic blood pressure was significantly
reduced at T25 in group H/A, compared with
group H, and in group O/A, compared with group O.
Prevalence of panting at T25 was 50% for groups H
and O, compared with 20% for group H/A and 30%
for group O/A. By T25, heart rate was significantly
lower in all groups. Oxygen saturation was unaffected
by treatment. Mean ± SD plasma histamine concentration
was 1.72 ± 2.69 ng/ml at baseline and 1.13 ±
1.18 ng/ml at T25. There was no significant change in
plasma histamine concentration in any group.
Conclusions and Clinical Relevance—Hydromorphone
is comparable to oxymorphone for preanesthetic
sedation in dogs. Sedation is enhanced by acepromazine.
Neither hydromorphone nor oxymorphone
caused an increase in plasma histamine concentration.
(J Am Vet Med Assoc 2001;218:1101–1105)