Drugs and Your Horse: The Dangers of Medicating

Improper use of some common equine drugs can impact our horses’ health and safety more than some might think.
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In the management of horse health, injuries, and disease, conscientious owners would never intentionally put their horse at risk; however, improper use of some commonly administered equine drugs can impact our horses’ health and safety more than we typically think.

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 and beneficial when used properly, but can be 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 can offer pain relief and help reduce 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.

These NSAIDs are invaluable medications, said Alison Moore, DVM, DVSc, Dipl. ACVIM, ACVSMR, 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 said.

Moore added that Bute is both economical and convenient and available in both injectable and oral formulations. But, she said, 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,” Moore said. “There’s health derived issues including gastric and colon ulcers, as well as renal (kidney) 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 signs, stop administering the medication and call the vet for diagnosis and treatment.

Flunixin meglumine (trade name Banamine) is also 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,” Moore noted.

Because of the deleterious effect chronic NSAIDs can have on horses, it is important not to “stack” them, or give more than one at the same time.

That Calming Effect

The list of tranquilizers, sedatives, and supplements intended to calm a horse is extensive and includes 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. 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,” Moore said. “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 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, Moore stressed 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

Compounding is the manipulation of a 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 their related risks came to light in 2009 with the high-profile deaths of 21 polo ponies at the U.S. Open Polo Championships in Wellington, Florida. After being injected with an incorrectly mixed compounded vitamin supplement 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,” said 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,” Moore said. “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.”

Moore explained that without careful attention to the appropriate dosage and administration, such as shaking the bottle properly so that no residue settles in the bottom, 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 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. Still, Moore suggested contacting your vet to develop a deworming program that is right for your horse and your specific area.

A Question of Welfare?

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 regards to 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; and
  • 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,” said 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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