Pr. Wilson et al., XYLAZINE AND A XYLAZINE FENTANYL CITRATE/AZAPERONE COMBINATION IN FARMED DEER .1. DOSE-RATE COMPARISON/, New Zealand Veterinary Journal, 44(3), 1996, pp. 81-87
Six 1-year-old farmed red deer were used to compare physiological and
behavioural responses to a range of doses of 5% xylazine with or witho
ut the addition of 0.4 mg of fentanyl citrate and 3.2 mg of azaperone
per mi. Each deer was randomly assigned to one of six treatments: xyla
zine alone at 0.4 and 0.6 mg/kg, the xylazine/fentanyl citrate/azapero
ne combination containing 0.2, 0.4 and 0.6 mg/kg of xylazine, or a ste
rile water control. Injections were given intramuscularly in the anter
ior neck, operator blind, on each of 6 sampling days between October a
nd January, such that each deer received all treatments with 9-28 days
between each treatment. Measurements included heart rate and respirat
ion rate. A 0-3 scoring system (normal to nil response, respectively)
was devised to record sedative responses (body stance, head position,
degree of eye closure, palpebral reflex, resistance to movement of the
head, response to noise) and analgesic responses to touch and pinchin
g of the ear, and response to a needle prick in the gluteal region. Sc
ores were added to produce a sedation score and analgesia score, respe
ctively, for each treatment. Records were taken immediately prior to i
njection and thereafter at 5, 14, 25, 35, 60, 90, 120, 150, 180, 210,
240 and 300 minutes. All deer given each dose rate of the xylazine and
the xylazine/fentanyl citrate/azaperone combination became recumbent.
There was a tendency for the time to recumbency and variation of time
to recumbency to be shorter at higher dose rates and with the additio
n of fentanyl citrate and azaperone to xylazine, particularly with xyl
azine at 0.4 mg/kg. These trends were not statistically significant (p
>0.05). The duration of recumbency was shorter with the low dose of th
e xylazine/fentanyl citrate/azaperone combination (0.2 mg/kg of xylazi
ne) than for the higher doses of xylazine alone or the combination of
drugs (p<0.05). There were no significant differences in heart rates o
r respiration rates between treatments, although all treatments signif
icantly reduced both heart and respiration rates (p<0.01). The sedatio
n scores showed similar peak responses and timing to peak responses (1
4-25 min) to both drug treatments and all dose rates, but the response
s were less persistent for lower doses. The analgesia scores showed a
similar pattern, with peak responses 14-35 minutes after administratio
n and more persistence at higher dose rates of both xylazine alone and
the xylazine/fentanyl citrate/azaperone combination. This study has s
hown that most physiological and behavioural responses to a range of d
oses of xylazine or the xylazine/fentanyl citrate/azaperone combinatio
n were statistically similar. However, there was a tendency for recumb
ency to occur more rapidly and with less variation in timing when the
mid-range dose of the drug combination was used, supporting the observ
ation by practitioners that the drug combination results in a more rap
id and reliable state of recumbency at a lower dose rate of xylazine.