Dexamethasone. There’s a good chance you’ve heard of it before, whether from your veterinarian or in the news. It’s a steroid fairly commonly used in all of veterinary medicine, including equine medicine. But recent cases of misuse have brought new attention to the drug, because the side effects can pose serious – even fatal – dangers to a horse.

So what is dexamethasone meant to be used for, what are the risks, and how can horse owners know when it’s safe to use the drug?

Intended uses

Dexamethasone is a glucocorticoid steroid that may be used as an anti-inflammatory or immunosuppressive agent. It can be given intramuscularly or intravenously (IV), but is most commonly given orally.

Annie King DVM, an equine veterinarian based in Calgary, Alberta, says that dexamethasone might be used in any case where they want to reduce inflammation. She’s seen it used most often for horses with asthma or other inflammatory lung diseases. It might be prescribed by veterinarians to treat a number of equine health issues, including:

  • allergic reactions
  • asthma
  • bursitis
  • chronic obstructive pulmonary disease (heaves)
  • hives
  • myositis
  • osselets
  • sprains
  • tendonitis

According to Plumb’s Veterinary Medication Guides, dexamethasone can help an animal feel better within 1-2 hours and clinical signs should improve after that time.

Potential consequences and side-effects

Like anything, dexamethasone comes with side-effects, which King says should be carefully considered by your veterinarian. “It can cause laminitis, which can obviously be devastating and fatal in some animals,” she warns.

Horses that are obese or have equine metabolic syndrome are going to be more susceptible to laminitis, King says, so vets would be more careful with using a steroid like dexamethasone for those cases.

King also notes that dexamethasone is an immune suppressant. “It might make an animal more susceptible to a secondary infection or an opportunistic pathogen,” she says. “An environmental pathogen, like a bacteria, may not cause any problems in a normal horse, but may suddenly cause a problem in a horse that’s immune-suppressed due to steroids.”

Dexamethasone may also cause poor wound healing when used at high dosages or long-term. Since it suppresses the immune system, a fever may not appear when there’s a serious infection; the only signs that something’s wrong may be low energy levels, a non-healing wound, or poor appetite.

Additional side effects may include:

  • anorexia
  • drowsiness
  • enzyme elevations
  • greater appetite, thirst and need to urinate
  • lethargy (for up to 24 hours)
  • mild behavioural changes
  • weight loss

Long-term use (lasting weeks or months) may also result in weight gain, skin and coat changes, and muscle weakness. Owners should watch for additional side-effects that may be a cause for alarm, such as horses going off their feed, a high fever, severe behavioural changes (such as aggression or threatening behaviours), and excessive appetite accompanied by weight loss. One or more of these symptoms may indicate their horse has developed stomach or intestinal ulcers, perforation, bleeding, or diabetes.

How it’s misused

There are increasing concerns that dexamethasone is being used in hunter circles because the side-effects may make a horse appear quiet and possibly place higher.

But who is administering it? It’s not uncommon for horse owners to be given various medications to administer to their horses themselves (for their intended purpose), or even extra doses for the next time there’s an emergency, which may be a necessity due to the remoteness of a farm or a shortage of equine vets available to attend emergencies.

“If owners have [dexamethasone] and they aren’t necessarily knowledgeable, they might use it in the wrong instances or the wrong dosages,” King says, “in which case you may have increased risk of those secondary effects [such as laminitis] that we don’t necessarily like to see.”

Dangers of misuse

The potential dangers of misusing dexamethasone can be serious and even fatal. King says she’s seen cases where an overuse of dexamethasone has caused an animal to have a founder episode or become acutely laminitic. In one case, a horse received an unknown amount of dexamethasone and “quickly and severely had a laminitic episode.”

“It is of course very, very painful,” King says. While that horse did survive, King says it was “one of those cases where it does make you really think about considering your case selection for steroid use.”

The risk of laminitis may be of particular concern in the hunter ring, where horses already tend to be slightly overweight. Two separate studies conducted in 2021, one at the USEF Pony Finals and another that surveyed 1,000 hunter judges across the United States and Canada, found that hunter judges tended to favour fatness and place horses carrying too much weight.

There are concerns that horse owners may be keeping their horses at a higher level of body fat than is healthy in order to score better in the show ring. It’s well known that being overweight is associated with increased risk of laminitis, which could make misuse of dexamethasone all the more dangerous for a hunter horse or pony.

Use appropriately

Although it comes with risks, King says that she doesn’t want horse owners to be afraid of dexamethasone. “Rightly used, steroids can be super useful and can be lifesaving in some cases,” she says. “It’s a medicine that can be helpful, but does carry a risk that should be discussed with your veterinarian.”

For Taylor Brooks, hunter coach and owner of Fox & Oak Farm in Ashton, ON, it’s important to have open and honest conversations between horse owners, trainers, and veterinarians.

“You only ever hear of the nightmares of horses who pay the ultimate price for abuse of the medications,” Brooks says. “A lot of owners aren’t aware, and I think honesty is the best policy.”

Tips for drug-free warmups

Brooks provided us with some tips that she and her students use to keep their horses and ponies (and themselves!) relaxed on show day and before going into the ring.

1) Warm up early in the day. If you have a horse or pony that’s especially nervous, or one that will be affected by a hectic warmup ring with lots of two-way traffic, announcements or music, warm up earlier in the day to avoid that busy environment.

2) If possible, flat in the show ring. Give your horse or pony a chance to trot through the empty standards and sniff flowerboxes the night before the show, especially if they’re prone to be more reactive to those impressively-built rings.

3) Lunge to get out any sillies. It can be overused, but when done well (with safe booting and good footing), Brooks says lungeing can help the horse get some energy out and get in a positive, working frame of mind.

4) Listen to your horse. Try to figure out what brings out the best in them, whether that’s warming up 30 minutes before the class, or waking up earlier and getting a couple of jumps in.

5) Less is more. If you’ve done the homework at home, Brooks says, you shouldn’t need more than a handful of jumps. Don’t teach a long riding lesson that adds to the stress of the environment.

6) Do a little confidence-boosting warmup. If you do have to warm up in a stressful or hectic environment, Brooks suggests taking one of the jumps closer to the outside of the ring at a trot or soft canter. You can also choose a smaller height that will produce positive results and instill confidence.

7) Take a minute in a quiet spot. If you’ve been warming up in a stressful environment, remove your horse from it and give them a moment or two at the in-gate before heading into the ring.

8) Stay relaxed yourself. Brooks suggests using visualization tools, watching another horse go, and keeping a positive voice in the back of your mind. By staying calm yourself, you’re better able to help your horse relax.