By Dr. Gail Mason, DVM, MA, DACVIM
Chief Medical Officer, Portland Veterinary Emergency & Specialty Care
Corticosteroids are a class of steroid hormones, also known as steroids or cortisone, that are naturally produced in the body by the adrenal glands. Glucocorticoids are involved in a wide array of activities in the body including the stress response, immune system response, reducing inflammation, and nutrient metabolism. Mineralocorticoids, such as aldosterone, the second type of steroid produced in the adrenal glands control total body water levels, blood pressure, and sodium and potassium electrolyte levels. Both types of hormones are essential for life.
Glucocorticoids are by far the most common type of steroid prescribed in veterinary medicine. There are numerous forms of prescribed glucocorticoids including prednisone, prednisolone, triamcinolone, betamethasone, dexamethasone, flumethasone, fludrocortisone, hydrocortisone, budesonide, and methylprednisolone. These related compounds primarily differ in their potency and their duration of effect within the body.
What are they used for?
Though sometimes maligned and feared, corticosteroids comprise one of the most useful therapeutic drug categories in veterinary medicine. Corticosteroids can suppress inflammation and in higher doses, allergic responses, and an overactive immune system. They also can be utilized in certain cancer treatments. For decades, corticosteroids have benefited humans and animals immensely. They are an essential part of treatment protocols for many life-threatening and disabling diseases. They also can reduce arthritis pain, and itching, and increase appetite, water intake, and weight gain in dogs that are battling chronic illness or cancer.
Most forms of corticosteroids that are prescribed to patients are synthetic (manufactured) and are several times more potent than the naturally occurring forms found in the body, and they typically last much longer. Glucocorticoids can be administered to the patient by injection, by mouth, topically, or by inhalation. Ideally, the specific type of dose and duration of use of the corticosteroid is chosen to block an abnormal process while minimizing side effects for the patient. In general, they should be used at a dose and interval to accomplish the goal, and then either tapered and stopped, or used at the lowest effective dose. It is interesting to note that veterinary patients are much more tolerant of corticosteroid use than humans, which is where some of the “negative press” stems from.
What are the side effects?
Short-term: The short-term side effects are those we expect a dog to experience when initially placed on corticosteroids. These side effects depend both on the type of steroids prescribed and on the duration that it is administered. Most commonly these include increased thirst and urination, panting (not trouble breathing), increased hunger (warning: counter surfing is common!), low energy, weight gain, and thinning hair coat. More rarely, corticosteroids can escalate aggression in those dogs with pre-existing dominance/aggression. If the side effects are problematic, your veterinarian may adjust the drug dose and interval of administration. The duration of use should be the minimum required to produce the desired effect. However, many instances require that a dog be maintained on the drug for longer periods, or even indefinitely. In that instance, most veterinarians will prescribe the lowest-effective dose, and at every-other-day dosing intervals. This allows the body to produce its own cortisol on the “off days” to keep the adrenals functioning. Your dog’s gastrointestinal condition may be treated chronically with budesonide, a cortisone drug that has less systemic effects and more direct action on the gut.
Long-Term Side Effects
Some disease processes and medical conditions require long-term treatment with corticosteroids, either at an anti-inflammatory or an immunosuppressive dose (the latter is generally 4 times higher). Side effects from long-term use become more of a concern, but with judicious monitoring, they can be minimized. Side effects most often seen with long-term corticosteroid use include weight gain, a pot-bellied appearance to the abdomen (due to muscle weakness), thinning of the muscles of the head (temporal muscle atrophy) changes in haircoat in either color or density, and rarely, firm skin plaques called calcinosis cutis. Many of these issues are reversible by discontinuing or lowering the dose of corticosteroid. While gastritis or gastric ulcers can occur, it is rare. Similarly, pancreatitis has been thought to be occasionally caused by corticosteroids, but proof of this is lacking.
An increased risk of diabetes mellitus is possible, though it is mostly in dogs with other risk factors. Perhaps the most important issue is long-term suppression of the immune system. Sometimes this is the “goal” of treatment when the dog’s immune system is producing inappropriate responses. However, decreased wound/tissue healing, as well as an increased susceptibility to infection are issues that should be monitored. Your veterinarian will likely keep close tabs on any patient on chronic corticosteroids. The drug should not be stopped suddenly, and/or without your veterinarian’s knowledge or consent. A withdrawal reaction can occur! Routine blood work and urinalysis are prudent monitoring tests. The urinary tract can be a source of low-grade infection and may go undetected because the typical bladder “inflammation” is being suppressed. In summary, glucocorticoids have a major place in veterinary medicine. If used correctly and monitored properly, the benefits should exceed the risks. So, do not fear them, but DO ask questions!!!