Horse Welfare Dexamethasone: Its Use, Misuse and Abuse Use of this valuable medication as a would-be quieting agent is not only unethical, it’s dangerous. Tricia Booker B y R i ck M i t ch e l l , DV M 42 Rick Mitchell, DVM, of Fairfield Equine Associates, Newtown, Connecticut, and Wellington, Florida, has a special interest in equine sports medicine, particularly lameness and performance problems. His clients include many nationally and internationally recognized trainers, and he’s served as the official veterinarian to the United States Equestrian Team for the Pan American Games, the World Equestrian Games and the Olympic Games. USHJA IN STRIDE / AU GUS T 2011 D examethasone, also known as Azium® and commonly referred to as “Dex,” is a medication frequently used in the performance horse. Technically speaking, it’s a corticosteroid belonging to the family of glucocorticoids and acts as an anti-inflammatory and immune system suppressant. Dex functions similarly to the natural hormone cortisol, but it’s synthetic and is 20 to 30 times more potent than cortisol. The anti-inflammatory effects of this medication can be used for significant benefit in the treatment of the classic signs of inflammation—redness, swelling, heat and pain. Dex is useful for the management of allergic disease, especially in the case of sudden and severe allergic responses such as hives or respiratory distress. Acute trauma, such as tendon strain or an eye injury, is often treated with this medication. Dexamethasone was combined with a diuretic (which is meant for reduction of swelling) in a product known as Naquasone®. This medication was often used to treat the swelling and inflammation associated with trauma. However, it’s no longer available in the United States as that brand-name product. Long-term, chronic immune-mediated conditions such as pemphigus (a dermatologic condition) and chronic respiratory problems such as “heaves” often respond well to long-term treat- ment with dexamethasone because of its immunosuppressive functions. Many otherwise healthy horses have been restored to competitive form with this medication. Serious Consequences Unfortunately, despite all of its possible benefits, frequent or long-term use of dexamethasone can have serious health consequences. Since it mimics the action of cortisol in the horse’s body, it will cause the same symptoms that excess production of cortisol does, namely Cushing’s syndrome. Those readers who have had a horse so affected may recall the problems with excess body fat, recurrent infections, lethargy, laminitis (founder) and poor body condition related to muscle loss (atrophy). Chronic dexamethasone use can do the same thing. Frequent use and sudden withdrawal can also have side effects. It’s not uncommon to encounter “runaway” infections of the skin and respiratory tract in horses that have been on extended doses of dexamethasone and other corticosteroids. Likely, the problem was there all along, but the symptoms of the disease were being suppressed by the corticosteroid. Once removed, the horse demonstrates more symptoms, sometimes very severe. And the infection may be more aggressive because the immune system has been suppressed. Because dexamethasone reduces inflammation, and inflammation can produce pain, it’s possible to modify a horse’s pain response to injury with the use of this medication. Dexamethasone use could also mask the subtle signs of soreness related to tendon or ligament injury; therefore, careful scrutiny of the horse’s soundness while medicated is important. Dex has a reputation for increasing laminitis risk, perhaps because of its immunosuppressive actions. Certainly there seems to be an anecdotal relation- ship, but no one has proven the exact mechanism of the relationship. The stressful environment of horse shows along with shipment can depress the horse’s immune system. Add a few doses of dex to that situation, and the horse may be even more susceptible to infectious disease or toxic events. Another thing to remember is that because it’s an anti-inflammatory medication, dexamethasone may affect some of the same functions as non-steroidal anti-inflammatory medications, and thus may produce additive effects that could have physiological consequences, such as gastrointestinal ulcerations when given concurrently with such medications as phenylbutazone (bute) or flunixin meglumine (Banamine). Administering dexamethasone in close proximity to long shipment really puts the horse at risk for serious stress-related and infectious disease. The United States Equestrian Federation therapeutic medications rule recognizes the medical benefits of dexamethasone and allows for its use in the competing horse. Its use is restricted to a dose equivalent to 20 mg for a 1,000-pound horse 12 hours prior to competition. Allergic conditions and other types of inflammation may respond quickly to dexamethasone, thereby returning the horse to full and normal function. There’s solid justification for its use in cases where a diagnosis is established. A Welfare Issue Dexamethasone has been perceived by many trainers, owners and some veterinarians to have a calming effect on horses. There’s weak evidence in labora- tory rats that this might be true, but no controlled studies exist in the horse to substantiate this effect. As a result of this belief, many horses are medicated with dexamethasone for horse showing with the intent of modifying behavior, but under the guise that the horse requires it for some allergic or other medical condition. While the medication is legal for use in competition under USEF rules, the intent of use for calming in the otherwise healthy horse is strictly forbidden. So, unless the horse has a disease problem, use of dex isn’t legitimate. Horses that are so medicated are often treated several days each week during the show season, and the effects of prolonged use may emerge. As mentioned earlier, these side effects may include weight gain, skin conditions, gastrointestinal upsets and respiratory disease, among others. Laminitis can occur in some instances, and this can have a permanent and debilitating effect. Administering dexamethasone in close proximity to long shipment really puts the horse at risk for serious stressrelated and infectious disease. The unwitting veterinarian (who hasn’t been informed of repeated dexamethasone use) who injects a joint with corticosteroids for an orthopedic problem may further contribute to immunosuppression that can lead to illness. Certainly, none of the above scenarios are in the best interests of the welfare of the horse. It’s clear that while dexamethasone is a useful therapeutic agent for certain conditions in the competing horse, it’s also a very potent agent, and it should be used only on the order of a veterinarian for conditions requiring treatment of inflammation or immune reaction. Misuse can lead to more health problems, and abuse as a wouldbe quieting agent is unethical and in violation of USEF rules. AU GUS T 2011 / USHJA IN STRIDE 43