Corticosteroids, commonly called steroids, can quickly alleviate many symptoms, making both the cat and the owner feel better. For example, they have anti-inflammatory properties and can stop most seasonal itching, whether from grasses, flea bites, or bee stings. They also can effectively control more serious symptoms, such as internal swelling from irritable bowel disease or an autoimmune disease.
In 2017, an interesting study published in the Journal of Feline Medicine and Surgery Open Reports discussed a 6-month-old cat with bilateral quadriceps contracture, a disease caused by fibrous adhesions in the muscles. After several failed conventional treatments, the Australian researchers tried supplementary corticosteroid (prednisolone) treatment and got immediate and sustained clinical improvement and long-term resolution.
But corticosteroids have two drawbacks: They usually only treat symptoms, and long-term use can cause side effects.
Of course, they’re usually only prescribed long-term when the benefit outweighs the risk. A cat with Addison’s disease (in which the adrenal glands don’t produce enough natural corticosteroid) needs life-long corticosteroid therapy to remain healthy.
Cats with some autoimmune conditions such as pemphigus, stomatitis, autoimmune hemolytic anemia, and asthma also may require long-term steroids. While other immunomodulating medications may be used, corticosteroids are often the easiest, safest, and least expensive option for many cat owners.
What Are Steroids?
Corticosteroids, also known as steroids or cortisol, are naturally occurring hormones produced by the adrenal glands, a pair of glands located near the kidneys. Steroids are vital for a multitude of normal functions, from reproduction and brain development to regulation of the immune response.
Two types of steroids are produced by the adrenal glands, glucocorticoids, which affect nutritional metabolism, and mineralocorticoids, which influence electrolyte levels and body fluid volume.
The most common steroid side effect is increased drinking and urination. Many cats also have an increased appetite, sometimes breaking into cupboards to raid the food. Rarely, cats might show gastrointestinal upset, with some vomiting or diarrhea. These side effects usually subside once your cat is off the medication.
Its important to realize that controlled inflammation is a good thing, as it plays a vital role in the immune system’s response bacterial, viral, and fungal infections. When steroids decrease inflammation, therefore, there is an increased risk of infections by these microscopic organisms. This risk increases with long term use of steroids.
Cats on long-term steroids tend to gain weight from the increased appetite and may lose muscle mass. Hair coats may become thin, and some cats will develop thin, fragile skin.
A study published in the American Journal of Veterinary Research showed that giving cats methylprednisolone (a steroid) for up to 24 days can cause changes in blood glucose values and plasma volume. These changes in hemodynamics may predispose cats to diabetes and congestive heart failure, although the latter is controversial.
What You Should Do
- Be sure to tell your veterinarian about all medications and supplements your cat is taking. For example, it may not be appropriate to administer corticosteroids at the same time as other drugs in the nonsteroidal anti-inflammatory category.
- Make all environmental changes necessary to help your allergic cat avoid the long-term use of these drugs.
- Discuss the pros and cons of corticosteroid administration with your veterinarian and keep your cat’s comfort levels at the forefront.
- If your cat is on long-term corticosteroids, be diligent about recommended regular veterinary checkups and monitoring.
Steroids can cause changes in blood chemistry panels and blood counts, sometimes complicating interpretation of these tests. Cats on long-term steroids may develop an increased white blood cell count, and blood glucose levels tend to go up in cats on steroids, which can make it difficult to distinguish between true diabetes and drug effects. Liver enzymes, cholesterol, and amylase levels may increase.
Thyroid levels, which are commonly checked in senior cats, can be affected by long-term steroid use.
“Chronic steroid usage effects most endocrine assays. Cortisol is the one most often thought of, but total T3 and total T4 are also affected. Potentially hyperthyroid cats receiving chronic steroids should be tested using free T4 by dialysis,” says Barb Schanbacher DVM, Animal Health Diagnostic Center, Department of Population Medicine and Diagnostic Sciences, Cornell University College of Veterinary Medicine. “Free T4 is less affected by long-term steroid use. If a cat is being weaned off steroids, it is recommended to have a two-week ‘wash-out’ period after steroids have been discontinued before testing.”
The diagnosis of Addison’s and Cushing’s diseases, characterized by decreased and increased natural corticosteroid production, respectively, can be complicated by steroid administration as well.
Urinalysis also can be affected by steroid usage. Many cats will have a glucose “spillover” into the urine, which can predispose to urinary tract infections.
What to Do
The first step in avoiding long-term side effects from corticosteroids is to avoid the long-term repository versions, such as methylprednisolone, if possible. Shorter acting, oral medications can be gradually tapered while still retaining their beneficial effects.
For conditions like asthma, switching to a nebulized, inhalant version of corticosteroids will reduce some of the risks associated with systemic drug administration. Cats can usually be easily conditioned to use the face masks required for the delivery of nebulized medications.
Your veterinarian may be aware of alternatives to steroids that can be used (some of them off label) to keep your allergic or arthritic cat comfortable. Joint and skin supplements can reduce the need for steroids, sometimes to just a short time of the year or intermittently. These medications may include some immunosuppressive drugs with side effects of their own, however, so caution may be required with them too.
The reality is that some cats will need long-term corticosteroids to manage severe, chronic illnesses. In these cats, owners need to balance the risk of possible side effects with quality of life, working in close collaboration with their veterinarian.