Steroid Treatment: Effects in Cats

What are steroids?

Corticosteroids, commonly called steroids, are hormones naturally produced in the adrenal glands. They help regulate many functions in the body, including the stress response, immune system activity, inflammation, nutrient metabolism, and electrolyte balance.

The adrenal glands produce two forms of corticosteroids:

• Glucocorticoids, such as cortisol, help control carbohydrate, fat, and protein metabolism. They also reduce inflammation through several mechanisms.
• Mineralocorticoids, such as aldosterone, help control electrolyte balance and the amount of water in the body, primarily by causing the kidneys to retain sodium.

Why are corticosteroids prescribed?

Because of their anti-inflammatory properties, corticosteroids are a valuable class of medications. They are commonly used to treat mild inflammatory conditions or to suppress the inflammation associated with an allergic response. When administered in high doses, they act as immunosuppressants, which means they suppress or prevent an immune response.

Most forms of prescribed corticosteroids are synthetic, and include prednisone, prednisolone, dexamethasone, triamcinolone, and methylprednisolone. These synthetic forms of corticosteroids are many times more potent than the naturally occurring forms found in the body and typically last much longer. Due to this potency and increased duration of activity, pets using these medications must be carefully monitored or serious side effects may result.

For decades, this class of drugs has benefited humans and animals. They are a vital part of the treatment protocol for many life-threatening diseases. Their benefits far outweigh any risks in most cases. When used properly, very few side effects occur.

What side effects can corticosteroids cause?

Corticosteroids have both short- and long-term side effects that cause different problems in your cat.

Short-term side effects

Short-term side effects depend on the type of steroid prescribed and on the dosage administered, and may include:

• Increased thirst and urination
• Increased hunger
• General loss of energy
• Development or worsening of infections (especially bacterial skin infections)
• Vomiting or nausea (less common)

Some pre-diabetic cats may become diabetic with corticosteroid usage. In many of these cases, the diabetes is resolved once the steroid is discontinued. In rare cases, patients with significant heart disease (which may or may not be diagnosed yet) can develop congestive heart failure. This is suspected to be caused by an increase in blood glucose that occurs with corticosteroid use.  

Increased blood glucose causes the kidneys to retain more water, increasing the fluid in the circulatory system.  If the heart can’t effectively move the larger volume of blood around the body, it pools in the vessels of the lungs and fluid from the blood leaks into lung tissue, causing heart failure.

If any of these side effects occur, they can often be eliminated by lowering the dosage or frequency of administration. In some cases, your veterinarian may prescribe another type of corticosteroid to reduce the side effects. The objective is to determine the lowest dose of medication that controls the condition with the least number of side effects.

Long-term side effects

Some diseases and medical conditions require long-term treatment with corticosteroids, at either an anti-inflammatory dose or an immunosuppressive dose. When corticosteroids are used for more than three to four months, particularly at immunosuppressive doses, additional side effects become a concern. The most common long-term side effects include:

• Urinary tract infections (UTIs), which occur in up to 30% of patients. Your veterinarian will perform periodic urine cultures to monitor for UTIs, because steroids suppress the usual UTI symptoms. 
• Thin skin, blackheads, and a poor hair coat
• Poor wound healing
• Development of obesity due to increased hunger
• Muscle weakness secondary to protein catabolism (breakdown)
• Hard plaques or spots on the skin called calcinosis cutis
• Increased susceptibility to bacterial infections
• Increased susceptibility to fungal infections (especially of the nasal cavity)
• Predisposition to diabetes mellitus

Can corticosteroids cause Cushing's disease?

An excessive level of corticosteroids may cause Cushing's syndrome (also known as hyperadrenocorticism or hypercortisolism). When a cat is on long-term, high doses of glucocorticoids, there is an increased risk that a condition called iatrogenic (medication-induced) Cushing's disease will develop. 

The clinical signs of Cushing's disease include increased thirst and urination, UTIs, skin and ear infections, a “pot-bellied” appearance, thinning skin, and hair loss. In the treatment of some diseases, the risk of iatrogenic Cushing's syndrome is unavoidable. To minimize this risk, corticosteroid doses are tapered down over time or several different drugs may be used in combination.

How do I reduce the risk of these side effects in my cat?

Fortunately, most cats can safely use corticosteroids if a few simple guidelines are followed. Avoid giving glucocorticoids daily except when specifically instructed by your veterinarian. Long-term daily use is generally reserved for life-threatening immune-mediated diseases require. Most corticosteroid treatment plans require daily use only during the initial treatment phase.

If your cat is receiving corticosteroids to reduce itching or relieve musculoskeletal pain, your veterinarian may recommend giving them every other day. If you feel your cat needs the medication every day, contact your veterinarian rather than changing the dosing schedule. Your veterinarian may recommend an additional or alternative treatment.

If your cat requires corticosteroids for longer than three to four months, your veterinarian should re-evaluated their condition and treatment plan. Cats receiving long-term corticosteroids should have an examination every three months and urine cultures and blood tests every six months.

Corticosteroids can be life-saving medications and improve quality of life for many cats. By working closely with your veterinarian, you can use these medications safely and provide your cat with the best possible care. Contact your veterinarian if you have any questions or concerns about your cat's medications.