Horse Medications -
Their Use and Contraindications
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Table of Contents
- Recommendations for the Proper Use
of Horse Medicines
- Related Links
Veterinarians are very influential in the decision making and activities
related to horse health. We have to remember the following facts
when dispensing medications (indicated in italics):
People remember only 20% of what they
When a veterinarian is called in to diagnose a problem with an
owner's horse, it is a very stressful time. Owners often focus on
their animal's problem, especially if it is colic or a major injury.
When veterinarians are dispensing a medication, it is time consuming,
but necessary, that owners focus on hearing and understanding the
instructions. It is the veterinarian's responsibility to ensure
that owners understand what the medication is, how often it should
be used and the route of administration. Some medications may need
to be given 2 or 3 times daily. Is the owner or barn manager available
to give the medication every 8 or 12 hours for 5 or 7 days in a
One third (1/3) of horse owners are new
to the horse industry.
Since many of our horse owners are new to the industry, veterinarians
need to show the owner how to load a syringe, where and how a needle
should be placed and ensure that the owner can give the medication
without endangering the health of the horse or themselves. The neck
bones run just above the jugular furrow, not just under the mane.
The landmarks for injection sites should be clearly recognized.
The injection triangle in the neck is easily identified as illustrated
in Figure 1.
Figure 1. The Most Common Intramuscular Injection
Points of the Horse
Equivalent of Drawing
Young people, especially teenage women,
are the main workforce of the industry.
Women of all ages, but particularly teenage women, are very active
in all levels and disciplines of the equine industry. Some medications
that are commonly used in and around the stable can affect the menstrual
cycle of women or impact on their health, including pregnancy.
Products such as Regu-Mate® can be absorbed after skin contact
and especially if wearing latex gloves. The manufacturer warns that
the following people should not handle this drug:
pregnant women, those with thrombophlebitis, coronary disease, women
with breast cancer, estrogen dependant neoplasia or undiagnosed
vaginal bleeding (1). Veterinarians should provide owners with a
written protocol for the proper handling of medicines. This protocol
can be hung in the barn for future reference. For further information,
refer to the factsheet, Human Health Concerns when Working with
Medications around Horses.
People have achieved a level of information
The internet has dramatically increased peoples' access to information.
At the touch of a fingertip, one can obtain information on virtually
every disease. Unfortunately, this leads to self-diagnosis, misuse
of medications, use of homeopathic products of variable and often
unknown effects and a blur of what are proper and recognized treatment
regimens. Penicillin G procaine and similar penicillin products
are available in two strengths, 200,000 and 300,000 IU per mL. The
recommended dose ranges from 10,000 - 20,000 IU/kg intramuscularly
every 6 hours to 22,000 - 40,000 IU/kg every 12 hours (1). For the
owner, the calculation of the correct dosage can be a major obstacle.
The following is an example. When using the 300,000 IU/mL
penicillin and when recommended to use the 22,000 units per kg dosage,
divide the strength (300,000 IU per mL) by the dosage per unit of
weight (22,000 IU per kg) to get the dosage of 1 mL per 13.6 kg
(300,000/22,000 = 13.6). Many owners have difficulty understanding
that a milliliter (mL) is the same as a cubic centimeter (cc).
Instructions should be given, clearly indicating the dosage (e.g.,
10 mL), how the medication is to be given (e.g., by the intramuscular
or subcutaneous route) and the frequency and length of usage (e.g.,
every 12 hours for "X" number of days). The number of
days will depend on the response of the bacteria causing the infection
to the medication. This is determined by the resolution of clinical
signs (e.g., a return to a normal rate and depth of breathing) and
a return to normal core body temperature (38 + 0.5°C).
People are more conscientious about their
own health and the health of the environment.
Over the past ten years, society in general and, more specifically,
horse owners are more conscious of the impact of improper antibiotic
use, the ground water and environmental impact of manure run-off.
The avermectin products, such as Eqvalan® and Quest, are
excreted from the horse and are reported to be quickly bonded to
the soil. Approximately one million doses of these dewormers are
used in Ontario each year and, since residues may adversely affect
fish and water-borne organisms, safe disposal of residual materials,
such as syringes, is important.
As we get older, the print on medication
bottles is getting smaller and harder to read, especially if we
are not carrying our glasses to the barn.
The size of print used on bottles of medications seems to be getting
smaller and smaller. Those of us that are over forty and having
a struggle with the "length of the arm" when reading and/or
are too proud to carry or wear reading glasses or, heaven forbid,
bifocals to the barn, have great difficulty deciphering "Is
that 1 cc per mL or 2?". Reading beyond the dose to the fine
print is out of the question. Warnings on the package inserts for
the avermectin products, Eqvalan® and Quest, caution the
user to "Wash hands after use." "Dispose of by burial
or incineration." "Avoid direct contact with skin and
eyes." These are rarely read or followed. Veterinarians should
provide readable instructions for every medicine dispensed.
The barn is not a suitable storage area
for medications, unless medications are protected from freezing
Medications should be stored according to the manufacturer's recommendations.
Some will require refrigeration but are not able to withstand freezing.
The barn window or bright shelf in the tack room may not be a suitable
storage location for medications that may be sensitive to light.
Recommendations for the Proper Use
of Horse Medicines
- Develop a client-patient relationship with a veterinarian.
- Listen to the instructions being given. Ask for written instructions
if the treatment regimen is complicated or being administered
by more than one person.
- On an annual basis, in consultation with your veterinarian,
complete a Horse - Medication Inventory Form,
which lists and gives instructions for all of the medications
that are stored on your farm. Links to a sample form and a blank
form can be found at the end of this information sheet.
- When new medicines are being dispensed, veterinarians should
provide the owner with complete instructions for the medication(s).
The easiest way to do this is to have an instruction sheet made
up (similar to the Medication Inventory Form) for a number of
the commonly dispensed medications. The animal to be treated would
be included in the "Treated Animal" column. A copy of
these completed forms should be included in the animal-owner's
Plumb DC. Veterinary Drug Handbook 4th ed. Iowa State Press, 2002.