In the management of horse health, injuries and disease, conscientious horse
owners would never put their horse at risk; however, improper use of some
commonly administered equine drugs can impact the health and safety of our
horses more than we think. Seldom does a month go by when media attention
doesn't focus on a positive drug test in the horseracing world. The news
leaves many in the horse industry to shake their heads and wonder how
trainers or owners could do such a thing to their animals. But did you know
that the majority of these positives involve some of the more commonly used
drugs that we administer to our horses on a routine basis and which can
produce some pretty unsettling results?
Under Diagnosis and Over Treatment
Used to relieve pain, allow or promote healing, and control or cure a
disease process, therapeutic medications can be effective when they are used
properly, but are quite dangerous when misused. Phenylbutazone, or "bute,"
is one of the most commonly administered prescription drugs in the
non-steroidal anti-inflammatory drug (NSAID) family. When used properly,
NSAIDs offer relief from pain and help in the reduction of inflammation and
fever. Found in the medicine kits of many horse owners, bute can be
prescribed for a plethora of ailments, including sole bruising, hoof
abscesses, tendon strains, sprained ligaments and arthritic joints.
NSAIDS are invaluable as a medication, says Dr. Alison Moore, lead
veterinarian for Animal Health and Welfare at the Ontario Ministry of
Agriculture and Rural Affairs in Guelph, Ontario. "When used appropriately,
they are very safe; however, some horse owners tend to give too much of a
good thing," she says. Dr. Moore goes on to say that this form of drug
(bute) is both economical and convenient, available in either injectable and
oral formulations; but is most likely to cause problems if given too long or
in improperly high doses, especially if horses are more sensitive to NSAID
"If you look at the chronic use of bute, there's certainly known
ramifications from it," says Dr. Moore. "There's health derived issues
including gastric and colon ulcers, as well as renal impairment. Renal
impairment is more prevalent in older horses that have developed issues with
their kidney function or with equine athletes that perform strenuous
exercise and divert blood flow from their kidneys. Chronic or repeated
dehydration is also a risk factor for renal impairment. Chronic exposure to
bute is more likely to cause signs attributable to the gastrointestinal
Clinical signs of toxicity include diarrhea, colic, ulceration of the
gastrointestinal tract (seen as low protein and/or anemia on blood work or
as ulcers on an endoscopic examination), poor hair coat, and weight loss. In
the event of such symptoms, the medication should be stopped and the vet
called for diagnosis and treatment. While a different type of drug, flunixin
meglumine (trade name Banamine), is found in the same NSAID family. "It's
not typically used as chronically as bute because it's more expensive and
mostly used for gastrointestinal , muscular or ocular pain, but if misused,
especially with dehydrated horses, kidney and digestive tract toxicity can
occur similarly to bute," Dr. Moore notes.
Because of the deleterious effect chronic NSAIDS can have on your horse, it
is even more important not to "stack" NSAIDS. This is the process where two
NSAIDS, usually bute and flunixin, or bute and firocoxib, are given at the
same time. Not only does the dual administration create gastrointestinal and
renal problems as listed above, but bute and flunixin given together can
cause a severely low blood protein that may affect interactions with other
That Calming Effect
The list of tranquilizers, sedatives and supplements intended to calm a
horse can be extensive, including some which can be purchased online or at
your local tack shop. For example, Acepromazine, known as "Ace," is commonly
used as a tranquilizer to keep a horse calm and relaxed by depressing the
central nervous system. It is available as an injection or in granular form
and does not require a prescription. If given incorrectly, it can carry a
risk of injury or illness for the horse.
"Tranquilizers can be used to keep horses quiet for training purposes or for
stalled horses due to injury, but it can be difficult to control the dose
when given orally," states Dr. Moore. "The difficulty with chronic
administration is you don't know how much you're dosing your horse or how
the horse is metabolizing it. Since it is highly protein bound in the
bloodstream, a horse with low protein may develop side effects more quickly
or react to a lower dose. Side effects include prolapse of the penis, which
is more of a problem in stallions, and low hematocrit, a measure of red cell
percentage in the blood. At very high doses, the horse will develop ataxia
[a wobbly gait] and profuse sweating."
As every horse is different, and the correct dosage needs to be calculated
based on the horse's weight and other influences, Dr. Moore stresses the
importance of having a vet oversee any tranquilizer use. It is also
important to inform the veterinarian of any acepromazine given to your
horse, as it can affect the outcome of veterinary procedures, such as
dentistry that requires sedation.
In equine medicine, compounding is the manipulation of one drug outside its
original, approved form to make a different dose for a specific patient,
whether it's mixing two drugs together or adding flavouring to a
commercially available drug. However, mathematical errors can occur. Last
July, Equine Canada issued a notice asking their members to use compounded
drugs with caution citing that because these medications are not available
as a licensed product, they may contain different concentrations compared to
a licensed product. There have been several instances where the medication
contained too little of an active ingredient, leaving it ineffective, or too
much, which can result in death.
Compounded drugs and its related risks came to light several years ago with
the high-profile deaths of 21 polo ponies at the U.S. Open Polo
Championships in Wellington, Florida in 2009. After being injected with a
compounded vitamin supplement that was incorrectly mixed, all 21 ponies
collapsed and died. "The biggest issue with compounded drugs is that many
horse owners are not often aware of what it means," says Dr. Moore. "They
think it's a generic form of a drug, but it's not. It's the mixing of an
active pharmaceutical ingredient, wherever it comes from in the world, with
whatever flavour powder or product the pharmacy or veterinarian puts
together. When going from one jar to the next, the concentrations could be
different. It could be twice the strength, and that's harmful or half the
strength and have little effect."
Because this process is not regulated with respect to quality, safety and
efficacy, there can be risks associated with compounding drugs.
"Technically, veterinarians are not supposed to dispense a compounded drug
if there is a commercially available product already, such as phenylbutazone
[bute]," says Dr. Moore. "If your vet felt that there was a therapeutic use
for a combination product of bute and vitamin E, then that is a legitimate
reason for compounding it. But a lot of people want to use compounded drugs
because they're cheaper. But cheaper doesn't necessarily mean better."
Dr. Moore explains that without careful attention to the appropriate dosage
and administration, such as shaking the bottle properly so that no residue
will settle in the bottom (or the last few doses will be extremely
concentrated), health issues can occur. Compounded medications have provided
a lot of benefit to horse health by providing access to products or product
forms that would be difficult to obtain otherwise, but because of the
concerns regarding quality control, horse owners should fully understand the
potential risks of using a compounded product and discuss these concerns
with their veterinarian.
In the past, traditional deworming programs didn't consider each horse as an
individual, as common practice was to deworm the entire barn on a fixed,
regular schedule. However, over the past 10 years, studies have shown there
is a growing concern regarding parasite resistance to dewormers.
Veterinarians now recommend that horses be screened for parasites by way of
a fecal egg test first instead of deworming with a product that may not be
effective against parasite burdens. A fecal exam is far safer than
administering deworming medications that they don't need. Dewormers are safe
when used properly, including testing first and using a weight tape for an
accurate dosage. Dr. Moore suggests contacting your vet to develop a
deworming program that is right for your horse and your specific area.
A Question of Welfare?
Horse owners should be aware of the more frequent reactions to drug use in
their horses and consider both the short term and long term effects before
use. Consideration of the horse's welfare should not only for the present,
but also for its future.
With the use of drugs and horses, it's important to:
- Proceed with the guidance of your veterinarian;
- Use the lowest possible dosage possible in order to achieve the desired results;
- Calculate the correct dosage based on your horse's body weight through the use of a weight tape;
- Closely monitor your horse throughout the course of treatment.
"It's being very aware of the use of our common, everyday drugs. As good a
drug as it is, when it's misused, negative effects will occur," says Dr.
Moore. "There's a greater importance on knowing the overall health level of
your horse. It's always best to have a good base point first, and because
the kidneys and liver are the two main organs that process medication, it's
important to know that those organs are working properly. That's why those
annual veterinary wellness exams are so important."
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