Effects of butorphanol and carprofen on the minimal alveolar concentration of isoflurane in dogs.
OBJECTIVE
To evaluate the effects of butorphanol and carprofen, alone and in combination, on the minimal alveolar concentration (MAC) of isoflurane in dogs.


METHODS
Randomized complete-block crossover study.


METHODS
6 healthy adult dogs.


METHODS
Minimal alveolar concentration of isoflurane was determined following administration of carprofen alone, butorphanol alone, carprofen and butorphanol, and neither drug (control). Anesthesia was induced with isoflurane in oxygen, and MAC was determined by use of a tail clamp method. Three hours prior to induction of anesthesia, dogs were fed a small amount of canned food without any drugs (control) or with carprofen (2.2 mg/kg of body weight [1 mg/lb]). Following initial determination of MAC, butorphanol (0.4 mg/kg [0.18 mg/lb], i.v.) was administered, and MAC was determined again. Heart rate, respiratory rate, indirect arterial blood pressure, endtidal partial pressure of CO2, and saturation of hemoglobin with oxygen were recorded at the time MAC was determined.


RESULTS
Mean +/- SD MAC of isoflurane following administration of butorphanol alone (1.03 +/- 0.22%) or carprofen and butorphanol (0.90 +/- 0.21%) were significantly less than the control MAC (1.28 +/- 0.14%), but MAC after administration of carprofen alone (1.20 +/- 0.13%) was not significantly different from the control value. The effects of carprofen and butorphanol on the MAC of isoflurane were additive. There were not any significant differences among treatments in regard to cardiorespiratory data.


CONCLUSIONS
Results suggest that administration of butorphanol alone or in combination with carprofen significantly reduces the MAC of isoflurane in dogs; however, the effects of butorphanol and carprofen are additive, not synergistic.
Ko
J C
JC
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Oklahoma State University, Stillwater 74078, USA.
Lange
D N
DN
Mandsager
R E
RE
Payton
M E
ME
Bowen
C
C
Kamata
A
A
Kuo
W C
WC
D000818:Animals; D002077:Butorphanol / Q000008:administration & dosage / Q000494:pharmacology*; D002227:Carbazoles / Q000008:administration & dosage / Q000494:pharmacology*; D018592:Cross-Over Studies; D004285:Dogs / Q000378:metabolism*; D004353:Drug Evaluation, Preclinical; D004347:Drug Interactions; D007530:Isoflurane / Q000378:metabolism*; D011650:Pulmonary Alveoli / Q000187:drug effects* / Q000378:metabolism; D011897:Random Allocation
D002227:Carbazoles; D007530:Isoflurane; C007005:carprofen; D002077:Butorphanol