WildLife Group
of the SAVA
Low Dose Opioid, Low Dose a2
Agonist (HH Regime) for
Immobilization of Large Wild Ungulates
Dr. Hendrik J Hansen
In twenty-one years of immobilizing wildlife in a very
busy mixed veterinary practice in Bela-Bela, Limpopo,
the challenge has always been to find the ideal
immobilizing drug dosage for each specific situation.
Then in 2013, a new challenge presented itself to every
wildlife veterinarian in a booming wildlife industry in
South Africa. Components of our basic drug group
on which we had relied on for the last four decades
became unavailable for long periods. This put our
livelihood as wildlife vets at stake, and even at times
prevented us from dealing with emergency cases such
as dystocias.
At this point, I decided to do a trial to investigate
alternative drug combinations for immobilization. My
main objective was to determine the lowest possible
opioid dose to produce safe, efficient immobilizations.
I set up a drug trial using African buffalo (Syncerus c.
caffer) The animals were immobilized for pregnancy
diagnosis, weaning, semen evaluation, horn
measurements and collection of blood samples. Two
hundred buffalo were divided into groups of five
animals per pen. Each group was immobilized with a
different drug combination.
Each animal had its drug combination recorded and
was carefully monitored during the immobilisation.
Downtime and subjective observations on safety
and effectivity of the anesthesia were noted. After
completion of the work, each animal received reversal
drugs and these doses and reversal combinations were
recorded. Combinations of reversal drugs were also
investigated to find a good combination.
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At first, I tested combinations of thiafentanil with either
azaperone, acepromazine, xylazine, medetomidine,
diazepam or ketamine with DMSO or hyalase.
From the results of these primary trials, it was decided
to continue exploring combinations of thiafentanil,
medetomidine and azaperone. I tested this combination
with a constant azaperone dose and tapering the
thiafentanil dose lower and the medetomidine dose
higher for each consecutive group. I repeated this
method according to the results of the previous group.
Always trying a lower dose of opioid. I carried on until
the opioid was left out at which stage the combination
results in less effective immobilization. By following
this method, I established the lowest safest and most
effective dosage range for thiafentanil, medetomidine
and azaperone combination for immobilization of
African buffalo.
No mortalities occurred during this trial and all the
procedures was successfully completed. Animals
immobilized was both sexes and ages from 6 months
to 16 years old.
I was very exiting with the results. The effective
thiafentanil and medetomidine dosages were both
much lower than what I anticipated on starting the
trail. It was also much lower than dosages that was
published for African buffalo for both drugs. The
combination also turned out to be safer immobilization
option than the combination that I traditionally used
for immobilizations. The potentiating effect of the
thiafentanil and medetomidine used in the optimal
dosage rates for every specie turned out to be better
than anticipated.