D Dexamethasone: Its Use, Misuse and Abuse

Horse Welfare
Dexamethasone:
Its Use, Misuse and Abuse
Use of this valuable medication as a would-be quieting agent is not only
unethical, it’s dangerous.
Tricia Booker
B y R i ck M i t ch e l l , DV M
42
Rick Mitchell, DVM, of Fairfield
Equine Associates, Newtown,
Connecticut, and Wellington,
Florida, has a special interest in
equine sports medicine, particularly lameness and performance
problems. His clients include
many nationally and internationally recognized trainers, and he’s
served as the official veterinarian to the United States Equestrian Team for the Pan American
Games, the World Equestrian
Games and the Olympic Games.
USHJA IN STRIDE
/
AU GUS T 2011
D
examethasone, also known
as Azium® and commonly
referred to as “Dex,” is a
medication frequently used in the performance horse. Technically speaking,
it’s a corticosteroid belonging to the
family of glucocorticoids and acts as an
anti-inflammatory and immune system
suppressant.
Dex functions similarly to the natural hormone cortisol, but it’s synthetic
and is 20 to 30 times more potent than
cortisol. The anti-inflammatory effects
of this medication can be used for significant benefit in the treatment of the
classic signs of inflammation—redness,
swelling, heat and pain.
Dex is useful for the management
of allergic disease, especially in the case
of sudden and severe allergic responses
such as hives or respiratory distress.
Acute trauma, such as tendon strain or
an eye injury, is often treated with this
medication.
Dexamethasone was combined with
a diuretic (which is meant for reduction of swelling) in a product known
as Naquasone®. This medication was
often used to treat the swelling and
inflammation associated with trauma.
However, it’s no longer available in
the United States as that brand-name
product.
Long-term, chronic immune-mediated conditions such as pemphigus (a
dermatologic condition) and chronic
respiratory problems such as “heaves”
often respond well to long-term treat-
ment with dexamethasone because of
its immunosuppressive functions. Many
otherwise healthy horses have been
restored to competitive form with this
medication.
Serious Consequences
Unfortunately, despite all of its possible
benefits, frequent or long-term use of
dexamethasone can have serious health
consequences. Since it mimics the action of cortisol in the horse’s body, it
will cause the same symptoms that excess production of cortisol does, namely
Cushing’s syndrome.
Those readers who have had a horse
so affected may recall the problems
with excess body fat, recurrent infections, lethargy, laminitis (founder) and
poor body condition related to muscle
loss (atrophy). Chronic dexamethasone
use can do the same thing.
Frequent use and sudden withdrawal
can also have side effects. It’s not uncommon to encounter “runaway” infections of the skin and respiratory tract
in horses that have been on extended
doses of dexamethasone and other corticosteroids.
Likely, the problem was there all
along, but the symptoms of the disease
were being suppressed by the corticosteroid. Once removed, the horse demonstrates more symptoms, sometimes
very severe. And the infection may be
more aggressive because the immune
system has been suppressed.
Because dexamethasone reduces
inflammation, and inflammation can produce pain, it’s possible to modify a horse’s
pain response to injury with the use of
this medication. Dexamethasone use
could also mask the subtle signs of soreness related to tendon or ligament injury;
therefore, careful scrutiny of the horse’s
soundness while medicated is important.
Dex has a reputation for increasing
laminitis risk, perhaps because of its
immunosuppressive actions. Certainly
there seems to be an anecdotal relation-
ship, but no one has proven the exact
mechanism of the relationship.
The stressful environment of horse
shows along with shipment can depress
the horse’s immune system. Add a few
doses of dex to that situation, and the
horse may be even more susceptible to
infectious disease or toxic events.
Another thing to remember is that
because it’s an anti-inflammatory medication, dexamethasone may affect some
of the same functions as non-steroidal
anti-inflammatory medications, and
thus may produce additive effects that
could have physiological consequences,
such as gastrointestinal ulcerations
when given concurrently with such
medications as phenylbutazone (bute)
or flunixin meglumine (Banamine).
Administering dexamethasone in close proximity to
long shipment really puts
the horse at risk for serious
stress-related and infectious
disease.
The United States Equestrian
Federation therapeutic medications
rule recognizes the medical benefits
of dexamethasone and allows for its
use in the competing horse. Its use is
restricted to a dose equivalent to 20
mg for a 1,000-pound horse 12 hours
prior to competition. Allergic conditions and other types of inflammation
may respond quickly to dexamethasone,
thereby returning the horse to full and
normal function. There’s solid justification for its use in cases where a diagnosis is established.
A Welfare Issue
Dexamethasone has been perceived by
many trainers, owners and some veterinarians to have a calming effect on
horses. There’s weak evidence in labora-
tory rats that this might be true, but no
controlled studies exist in the horse to
substantiate this effect. As a result of
this belief, many horses are medicated
with dexamethasone for horse showing
with the intent of modifying behavior,
but under the guise that the horse requires it for some allergic or other medical condition.
While the medication is legal for
use in competition under USEF rules,
the intent of use for calming in the otherwise healthy horse is strictly forbidden. So, unless the horse has a disease
problem, use of dex isn’t legitimate.
Horses that are so medicated are often
treated several days each week during
the show season, and the effects of prolonged use may emerge.
As mentioned earlier, these side
effects may include weight gain, skin
conditions, gastrointestinal upsets
and respiratory disease, among others.
Laminitis can occur in some instances,
and this can have a permanent and debilitating effect.
Administering dexamethasone in
close proximity to long shipment really
puts the horse at risk for serious stressrelated and infectious disease. The unwitting veterinarian (who hasn’t been
informed of repeated dexamethasone
use) who injects a joint with corticosteroids for an orthopedic problem may
further contribute to immunosuppression that can lead to illness.
Certainly, none of the above scenarios are in the best interests of the
welfare of the horse.
It’s clear that while dexamethasone
is a useful therapeutic agent for certain
conditions in the competing horse,
it’s also a very potent agent, and it
should be used only on the order of a
veterinarian for conditions requiring
treatment of inflammation or immune
reaction. Misuse can lead to more
health problems, and abuse as a wouldbe quieting agent is unethical and in
violation of USEF rules.
AU GUS T 2011
/
USHJA IN STRIDE
43