Drugs and Your Horse- The Dangers of Medicating

By: Barbara Sheridan, Equine Guelph

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 horse racing 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 toxicity.

“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 tract.”

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 medications.

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.

Drug Compounding

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 flavoring 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 flavor 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.

Deworming Strategies

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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