Another benefit was that shortages of potent opioids
had less impact on my work as veterinarian.
I then started to adapt and investigate low opioid - low
α2 agonist combinations for other species. On average,
no more than 10-20 % of the traditional potent opioid
dosage is used in any species. Since 2014, I have
immobilized more than 10 000 animals with these drug
combinations. Although thiafentanil is now readily
available, I still use these combinations because, in my
opinion, it is much more effective and much safer than
the traditional combinations in most situations.
The low Opioid low α2 drug regime
Medetomidine has high affinity for α2 receptors
and has 10 times the binding specificity for these
receptors that xylazine. In addition, it has reduced side
effects such as bloating, regurgitation, abortions and
thermoregulatory depression compared to xylazine.
Opioids and α2 agonist drugs act synergistically, and
thus together have potentiated anesthetic effect.
Advantages:
1.
2.
3.
4.
More antidote possibilities for specific situations
– such as tailoring combinations for debilitated
animals or animals being transported different
distances. One can reverse the medetomidine
with either yohimbine or atipamezole for different
levels of anesthesia and the thiafentanil at very
low dose will keep the animal down but in a lower
plane of anesthesia.
Better muscle relaxation earlier in anesthesia.
(e.g. roan bulls) This benefit the animal as most
heat production in immobilization happens duo
to muscle rigidity/tremors. I found that animals
might take a few minutes longer to go down, but
their temperature remains lower than with the
traditional combinations.
Improved thermoregulation due to better muscle
relaxation. I found this combination safe at
even high ambient temperatures. I did not take
humidity into account and this is a subjective
observation.
Reduced occurrence of capture myopathy in
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
comparison with cases where I used high dose
opioid without medetomidine.
Safe in pregnant animals. I immobilized at least
600 pregnant buffalo cows without observing
any abortions. For one auction I immobilized
64 pregnant cows for disease testing twice and
took them to a boma. The same animals were
immobilized again to load 30-60 days later and
all of them were again confirmed pregnant. 142
sable cows tested for pregnancy on one farm and
all of them calved down in that season.
Better for semen collection in bulls when used
without the azaperone.
Better for walking of animals to safer area for
loading or working. The darted animals can very
easy be walked in the few minutes before the go
down, or soon after going down by using cattle
prodder to get then to stand up.
Safe anesthesia
Less need for ‘top-up’ ketamine doses.
Safer in debilitated animals. The atipamezole can
be given immediately and still have 30 minutes
plus to work with the animal only under low dose
thiafentanil which is very safe for old or debilitated
animals.
Less bloating, regurgitation or rolling. (e.g. buffalo)
Safer to use in long immobilization procedures.
(e.g. caesarian section)
Tranquilization regime for easier transport in most
species. For example: In spiral horned species do
not give yohimbine or atipamezole after loading.
This animals remain very calm for transport
purposes.
Animal handling less stressful as they become
less responsive and unaware much earlier in the
immobilization process.
Much more cost effective.
Disadvantages:
1.
2.
Some species need atipamezole/yohimbine
antidote. Roans, sables and waterbuck will
need atipamezole, yohimbine or a combination
otherwise they might go down again after opioid
reversal.
Slightly longer downtimes.
2020
ISSUE 01
7