Glucocorticoids, or “steroids,” are commonly used to treat disease in cats, and they can improve—and even save—your cat’s life. While they are an important tool for your veterinary team, there are some side effects of their use that you should understand. A good example of the benefits of glucocorticoids is their use in treating certain feline cancers.
“Prednisolone (a commonly used glucocorticoid) is often used as part of a multi-agent chemotherapy protocol to treat various types of lymphoma,” says Dr. Kelly Hume, associate professor in the section of oncology at Cornell University’s College of Veterinary Medicine. “It can also be used as a single agent in a palliative-care setting, when chemotherapy isn’t feasible for an individual family and their cat.”
Glucocorticoids are also used to treat a variety of diseases that involve activation of the immune system and/or inflammation, including allergies to inhaled allergens or fleas, asthma, inflammatory bowel disease (IBD), hypersensitivity reactions/anaphylactic shock, autoimmune diseases, and certain neurologic diseases.
These drugs are truly a mainstay of medical therapy in both animals and people, but they do cause side effects in some cases.
Short-Term Side Effects
The short-term side effects of glucocorticoids in cats include weight gain, diarrhea, and mood changes. They can also make managing diabetes difficult, so they are not recommended for cats with pre-existing diabetes. In some cases, their use may contribute to the onset of diabetes.
When glucocorticoids are used long-term, there is increased concern for a variety of harmful side effects, including:
- Dull dry hair coat
- Hair loss (alopecia)
- Thin, fragile skin
- Muscle wasting
- Stomach ulcers
- Pancreatitis
- Vomiting and diarrhea
- Loss of appetite
- Hypertension (high blood pressure)
- Diabetes
- Urinary tract infection (UTI)
- Iatrogenic Cushing’s syndrome
The higher the dose, the greater the risk of side effects. Doses prescribed for inflammatory 
disorders are generally lower than for immune-mediated or neoplastic conditions, making the likelihood of side effects less for these cases. The best way to minimize the side effects of glucocorticoids is to use the lowest effective dose that will manage whatever condition is being treated by your veterinarian.
There are certain health conditions besides diabetes that glucocorticoids can make worse, so they should be avoided or used carefully in cats with these conditions, including:
- Congestive heart failure. Glucocorticoids cause fluid retention, which can worsen heart failure.
- Chronic kidney disease (CKD). Many cats with CKD have hypertension that can be worsened by the fluid retention that glucocorticoids can cause.
- Hypertension. See above.
- Infectious diseases. Glucocorticoids can inhibit the immune system (which helps protect against invading organisms, like bacteria, viruses, and fungi), making cats more vulnerable to infections.
Glucocorticoids should never be given to pregnant cats as they may induce abortion, premature labor, dystocia (difficult labor), stillborn kittens, and retained placenta. They should also be avoided, if possible, in nursing queens, as they can be passed through the milk to the kittens.
Glucocorticoids should not be given with non-steroidal anti-inflammatory drugs (NSAIDs), as this combination is highly likely to result in gastric ulcers, which may be severe.
Caution should be exercised when giving them to cats that are receiving certain diuretics (i.e., furosemide), as this combination can cause significant potassium loss.
Tapering the Dose
When glucocorticoids are administered, it is critical that when discontinuing them, they are slowly tapered as opposed to stopping cold turkey. When they are given, the patient’s adrenal glands can become less active. This can happen even within the first week or two of treatment.
Withdrawing steroids suddenly can leave a cat with inactive adrenal glands that produce little or no glucocorticoids, which are essential for life. In this situation, since no glucocorticoids are being given to the cat and none are being produced by the adrenal gland, a potentially life-threatening lack of glucocorticoids can result.
Gradually tapering glucocorticoids over time allows the adrenal glands time to return to normal function. It is important that no changes to the dosing of glucocorticoids are undertaken without veterinary consultation.
Veterinary monitoring of feline patients while they are on glucocorticoids with physical examinations, bloodwork, and urinalyses is important to avoid harmful effects. If any are observed, a lower dose or an alternative drug may be considered.
Bottom Line
Glucocorticoids are an invaluable tool to treat a variety of diseases. Given their potential side effects, though, other therapies may be pursued first. Your veterinarian will discuss all your options, go over the pros and cons of corticosteroid therapy, and help you make the best overall decisions for you and your cat.
